Dossie 1758
[Robert Dossie], The Handmaid to the Arts, London [John Nourse] 1758.
Robert Dossie (1717–1777) was an English chemist and technologist from Sheffield. Trained as an apothecary, he later worked in various industrial centres across England. In 1760, with the support of the writer Samuel Johnson (1709–1784), he became a member of the Society for the Encouragement of Arts, Manufactures, and Commerce, founded in 1754. Dossie authored several substantial treatises on chemistry and various technologies, which were translated into several European languages. His extensive treatise Handmaid to the Arts (1758) ranks among the most detailed early modern texts on artistic techniques and materials. From this book we present selections concerning the nature and preparation of pigments, several painting techniques, the mixing of colours, and fresco painting. However, by “fresco,” Dossie understood not only painting on wet plaster but monumental architectural painting in general, whether executed on plaster or on canvas.
pp. 1–3
PART I.
OF THE
MATERIA PICTORIA:
OR,
The nature, preparation, and use of all the various substances employed in painting.
CHAP. І.
Of the substances in general used in painting.
THE principal kind of substances used in painting is the COLOURS: by which, is to be understood, all the various bodies employed by painters, for producing the difference of hue or teint: but, as several of these are of a solid consistence, and an earthy, or incohering texture, it was necessary, as well for the laying them on, and spreading them properly, as for the binding and making them adhere to the grounds on which they are laid, that, in many cases, somewhat of a fluid nature should be added to give them an unctuous consistence while used, and proper degree of tenacity when again dry: and, to this end, many different kinds of bodies have been applied; from whence proper VEHICLES have been formed, which, at the same time, answer the double purpose of reducing the colours to a state fit for their being worked with the brush or pencil, and of cementing them to each other and the ground they are laid upon; as also of defending them from being easily injured by accidents.
The substances used in painting may be therefore all considered as of these two kinds; Colours and Vehicles. For, though there are several used occasionally, which are not immediately subservient to the principal intentions of vehicles; yet, being employed to remedy the defects of those which are, they must be considered as subordinate to them; and ought, consequently, to be classed with such as compose vehicles.
The nature of these secondary intentions, I shall, therefore, point out in its due place; and reduce the substances serving to them to their proper classes accordingly: as it is necessary, in order to understand critically and completely the art of preparing and using the various articles of the materia pictoria, to comprehend clearly the general intention in which each is used, as well as to know the particular purpose to which it is applied. And, for the same reason, as also for the sake of being intelligibly concise, I shall treat of the whole under such methodical distinctions as refer to these intentions: adopting, nevertheless, on every occasion, the terms of art in common use; and explaining them, according to the meaning they bear when applied with any propriety or precision, by the particular relation they have to these intentions.
pp. 3–12
CHAP. II
Of Colours.
SECT. I.
Of colours in general.
COLOURS may be either PIGMENTS or fluids. By pigments, is meant all such solid bodies as require to be mixed with some fluid, as a vehicle, before they be used as paints, (except in the case of crayons, where they are used dry.) These make the far greatest part of the whole: the fluid colours being only a small number employed along with water colours; and asphaltum, which is sometimes employed in oil painting.
Colours are distinguished into several kinds, according to the vehicles in which they are worked; as oil colours, water colours, enamel colours, &c. As the same sorts of pigments, however, are, in many instances, employed in more than one kind of painting, as vermilion and lake in several, and ultramarine in all. I shall not distribute them into classes, in that view, till I come to speak of their particular application; but treat at present of them promiscuously in teaching their general nature and preparation; dividing them according to their affinity in colour only; since this method of arrangement will not only render each article more easy to be found; but, at the same time, exhibit to the artist together the whole stock of every kind from whence he must take what he wants on each occasion: by which, he will be the more enabled, to chuse what may best suit his particular purpose. For the same reason, also, this method is certainly more expedient than the disposing them in classes, according to their natural relation to each other, as earths, minerals, vegetables, &c; which would lead to the like kind of confusion and repetition.
The principal qualities in colours, considered with regard to their perfection or faultiness, are two; purity of colour, and durableness: purity of colour is, by the painters, called BRIGHTNESS; and the defect of it FOULNESS, or sometimes the BREAKING THE COLOUR: durableness is called STANDING; and the negation or want of it FLYING or FLYING OFF; which terms, for conciseness, I shall use in speaking of these qualities.
Brightness and standing well are the only properties, which are necessary to the perfection of every kind of colours; and they equally relate to all; but there are others, which are essential to many sorts, with regard only to particular purposes and uses: such of them, however, as do not fall within the general consideration of the nature of colours, will be treated of in those parts of the work where the particular uses of colours come in question.
The most considerable of the more general properties of colours after purity and durableness, or brightness, and standing well, are transparency and opacity; for according to their condition, with respect to these qualities, they are fitted to answer very different kinds of purposes. Colours which become transparent in oil, such as lake, Prussian blue, and brown pink, are frequently used without the admixture of white, or any other opake pigment; by which means, the teint of the ground on which they are laid retains in some degree its force; and the real colour, produced in the painting, is the combined effect of both. This is called GLAZING, and the pigments indued with such property of becoming transparent in oil, are called glazing colours. The same holds good also of such colours as are transparent in water; only when they are there used in this manner, they are not called glazing but WASHING colours. When colours have no degree of such transparency in the vehicle in which they are used, as vermilion, King’s yellow, and several others, they are said TO HAVE A BODY, and TO COVER. The property of glazing or washing is of so much importance, both in oil and water, that no other method can equally well produce the same effect in many cases, either with regard to the force, beauty, or softness of the colouring: and it is therefore very essential to the perfection of several kinds of pigments, that they should possess this property in a complete degree; but, in other instances, the using colours with a strong body is not less necessary, especially for the grounding or laying in, as it is called, of many objects to be painted.
There is another material quality in colours, that relates only to their use in oil, which is the drying well and (as it is called) not fattening. By FATTENING is meant, a coagulation of the oil, that frequently happens on its commixture with several kinds of pigments, by the effect they have upon it; from whence, after some time keeping, it is rendered of so viscid or glutinous a consistence, as to be wholly incapable of being worked with either brush or pencil. This quality, when found in them, destroys almost wholly the value of such pigments for the purposes of the colourmen; who sell a great part of them ground with oil, and tied up in pieces of bladder, where they are kept till there is a demand for them; which frequently does not happen soon; and, therefore, gives time for their spoiling in consequence of this quality. But to painters, who mix the colours for themselves, on their pallets, with the oil, this property is not an equal inconvenience, when in a lesser degree; only, in general, it must be observed, that colours, in proportion to their tendency to fatten, are flow in drying; and when the oil once contracts this state, it will be a very long time before it will become duly hard and firm in the paintings.
There are two other qualities of colour in general that relate only to their teint or hue; but which render them nevertheless fit or improper, in a very material degree, for different purposes. They are distinguished by the names of WARMTH and COOLNESS: terms which indeed are used very frequently by painters; but, for the most part, very indefinitely, and without any precise or clear meaning. What is meant, when properly used, by warmth, is that fiery effect which a small addition of yellow gives to a true red, and that glowing appearance which red imparts to either yellow or blue. By warmth, therefore, in red, is to be understood a small inclination towards orange; by the same term, applied to yellow, a like tendency by the admixture of red; and, by the same, again in the case of blue, must be understood its slightly verging on the purple.
By coolness, is to be understood, the opposite to warmth; but this term is seldom used, except in speaking of yellow and blue; and there it means, either the negation of that which causes warmth, or a tendency to green, in either colour, by a slight admixture of the other.
The sense of the word warmth, when applied to colouring or the combined appearance of various teints, must not be confounded with that, which it has when speaking of particular colours; for there it relates to the producing a strong effect, by the disposition or contrast of the colours, or the grossness of the teints, and not the qualities peculiar to, or inherent in the colours themselves.
The colours used in all the several kinds of painting, except some peculiar to enamel, are, as follows.
| RED. | CLASS I. Vermilion. Native cinnabar. Red lead. Scarlet oker. Common Indian red. Spanish brown. Terra de sienna burnt. Carmine. Lake. Rose pink. Red oker. Venetian red | Scarlet or tending to be orange. Crimson or tending to be purple. |
| BLUE. | CLASS II. Ultramarine. Ultramarine ashes. Prussian blue. Verditer. Cendre blue or sunders blue. Indico. Smalt. Bice. Litmus or lacmus. | |
| YELLOW. | CLASS III. King’s yellow. Naples yellow. Yellow oker. Dutch pink. English pink. Light pink. Gamboge. Massicot. Common orpiment. Gall stone. Terra de sienna unburnt. Turpith mineral. Yellow berry wash. Turmeric wash. Tincture of saffron. | |
| GREEN. | CLASS IV. Verdigrise. Distilled verdigrise, or chrystals of verdigrise. Prussian green. Terra verte. Sap green. | |
| ORANGE. | CLASS V. Orange lake. | |
| PURPLE. | CLASS VI. True Indian red. Archal. Logwood wash. | |
| BROWN. | CLASS VII. Brown pink. Bistre. Brown oker. Umbre. Cologn earth. Asphaltum. Spanish juice or extract of liquorice. | |
| WHITE. | CLASS VIII. White flake. White lead. Calcined hartshorn. Pearl white. Troy white. Egg-shell white. | |
| BLACK. | CLASS IX. Lamp black. vory black. Blue black. Indian ink. |
These are all the colours at present in use, in this country, in any kind of painting, except such as are peculiar to enamel; in which kind of painting, as but few of these are capable of combining with glass, and enduring the necessary heat without changing their nature, or being destroyed, others are employed more suitable to vitrification: for which reason, as the compositions for forming the enamel colours are very various, and bear no particular names, and the management of them has very little relation to other kinds of painting, I shall omit speaking of them till I come to treat particularly of enamel painting.
Of the above enumerated colours, but few are in universal use; most painters having only a select set out of them, and being, in general, unduly prejudiced against those they reject: and some of the best of them, as scarlet oker, terra de sienna, terra verte, true Indian red and umbre in oil painting, and bistre and gall stones in water painting, are, either through their scarcity, or the ignorance which prevails concerning their qualities, at present very little regarded; though some of them were formerly in common use; and all of them might be so with great advantage to the art.
It is no little impediment to their improvement in the profession, that painters are not more extensively acquainted with all the substances fit for their purposes; and more minutely informed of the good as well as the bad qualities of what colours they might use: for many labour under great disadvantages for want of a more copious choice, and the not being better apprized of some of those which suit their own particular manner of working; and which would, in many cases, remove difficulties out of their way, by enabling them to produce effects by more simple methods, and such as are yet more correspondent to their manner, than those they are now obliged to persue from their defect of proper colours.
As colours are obtained from very various substances, the means of preparing them are, consequently, very various: some being of a simple nature, and requiring only to be purified, and reduced to a proper consistence or texture; and others being compounds of different bodies, to be formed only by complex and elaborate processes. It is therefore very difficult to give such general directions, for the making every sort of colour, as may be intelligible to all; the utensils to be employed, as well as the methods to be persued, being such as belong to different arts and trades: but as the greater part may be done most commodiously by adopting the methods used for performing the common chemical processes, it is the most expedient way to treat of them correspondently to such a view: as, by that means, any who may make themselves acquainted with the common practice of chemistry, for which there are a number of books that afford sufficient assistance, may easily understand the whole art of making colours when taught in this manner. For the sake, however, of those, who may want leisure or disposition to proceed by this method, I will prefix such a description of the instruments, and explanation of the general nature of the operations, as together with the particular directions given in each process, may enable even such as are wholly ignorant of chemistry, if they give a due attention, to get over this difficulty: as indeed, without such a previous knowledge of the nature of the instruments and operations, it would be impracticable to attempt to prepare several of the most valuable colours.
Where, nevertheless, simple means, and the use of such utensils as are generally known, may be sufficient to perform what is wanted; I shall avoid all technical terms, and more complex methods of operation; confining myself to such a manner of instruction, as may be universally intelligible.
pp. 12–29
SECTION II.
Of the utensils, instruments, &c.
subservient to the making and preparing colours.
THE apparatus or set of utensils, &c. necessary for making the several colours used by painters, consists of, a furnace for subliming vermilion – another for subliming King’s yellow – a third for calcining ultramarine, the coal for Prussian blue, okers, &c. – sublimers – a pewter boiler with its proper furnace – a balneum mariæ – filters – boards for drying the pigments – levigating mills, stones and mullars – with several other smaller implements subservient to these.
As several of these implements are in common use for other purposes, and consequently to be had ready made of a proper constructure, I shall only enumerate them, without entering on any particular description of them: but with respect to that part of the apparatus, which relates to the more secret arts of making several of the colours, and has any thing peculiar in its fabrication, I will endeavour to give such a conception of the proper figure of every particular, and such directions for their construction, as may enable any to procure them to be made by proper workmen. As, without this previous information of the necessary means of performing them, the giving the recipes or processes alone for making the colours would be of very little consequence: and as, by this method, I avoid the necessity of repeating frequently the instructions for those particulars, which when given in a more general way will serve effectually for a multiplicity of occasions.
Of furnaces.
The furnaces are of the most difficult construction of any part of the apparatus for making colours; being most remote from common experience and conception: and yet it is indispensibly requisite, that they should be completely adapted to the purpose they are intended for. I shall therefore be most particular in my directions concerning them: but, before I enter on that task, it may be previously necessary, to teach the manner of making a composition, which I shall have occasion to direct the use of frequently in my instructions for the building them, as well as on other occasions. I mean the lute for making good the junctures that suffer a great heat, and securing bodies of a tenderer nature from the effects of the fire; which I shall call here, as is done elsewhere, the fire-lute: the composition of which is as follows.
“Take of green vitriol, or copperas, any quantity; and put it into an earthen pipkin, of which it may fill only three parts, and set it on a common fire; taking care that it may not boil over; which will be very liable to happen if the fire burn too briskly. When it has almost done boiling, throw in more of the vitriol, the quantity at first thrown in being now shrunk and contracted; and let that also boil to dryness; and repeat this till the pipkin be near full of the dried matter: raise the fire then round it; and let it continue in as strong a heat as can be conveniently made, till the whole contents become of a red colour; after which take it out of the fire; and, being cold, break the pipkin, and separate the calcined vitriol from it. Take then of this calcined vitriol powdered two parts, of the scoria or clinkers of a smith’s forge, finely levigated, – Sturbridge clay or Windsor loom dried, and powdered, – and fine sand, each one part: mix them well together; and then temper them, with the blood of any beast, till they become of the consistence of mortar; a twentieth part of the weight of the whole of short hair being beaten up with them.”
The furnace for vermilion, as well as the operation to be performed in it, are of the most nice nature of any objects relating to the art of making colours: it is indeed so difficult a thing to manage well the manufacture of vermilion, that it is given up in general in this country, even when the price of quicksilver would make it very profitable; and the greatest part, if not the whole of the consumption, is supplied from Holland: but if any will prepare well the apparatus as here directed, and execute properly the process given below, they need not doubt, with some experience, but to be able to carry on this manufacture as well as the Dutch. The manner of constructing the furnace may be as follows.
The first step must be to procure the proper iron-work, which consists of bars for bearing the fewel, – a frame, – doors for feeding the fire, – a strong plate for supporting the brickwork over them, – an iron frame and stopper for feeding the fire, and an iron ring for laying over the top of the furnace, for the better hanging the bodies or subliming vessels in it.
The bars should be of hammered iron, eight in number, eight inches in length, a quarter of an inch in breadth, half an inch in depth, and fixed firmly by each end, at the distance of a quarter and a half quarter of an inch from each other, into two strong cross-bars; which cross-bars must be sufficiently long to admit of their suffering the brickwork to have good hold of them; and must be made flat at their ends, on that account.
The frame and door must be also of hammered iron. They must be of the length of the area or fire-place as formed by the bars; but need not be more than four inches high. They may be of the usual form of those made for the furnaces of coppers, but stronger; and it is better to have the latch bigger than is common, and carried across the whole door; which will give it strength to resist the weight of the fewel, that, otherwise, when the iron is softned by violent heat, is apt to force the middle part outwards.
The iron bar to lay across the frame of the door may be three inches in breadth; and about three inches longer than the frame itself: it may be either of cast or hammered iron, as shall be found most easy to be procured. The frame and stopper for feeding the fire should be also of hammered iron: the frame may be four inches long, and three inches high. It may be formed of four plates of a moderate strength; of which those of the top and bottom must slope downwards towards the fire in a parallel; they must also project beyond their joining with the side plates; in order to their being fixed in the brickwork. The stopper must be formed of five plates, put together in fashion of a box; (as in the doors of portable iron furnaces;) and of such figure and proportion, as to slide into the hole formed by the frame, and fill it up exactly, so as to render that part of the furnace intire, when it is not taken out occasionally to feed or stir the fire. The hollow of this box or stopper must be turned towards the fire; and filled with fire lute; and a handle must be fixed in the middle of the outward part, for the more commodious use of it when hot.
The iron ring for hanging the bodies or subliming vessels in the fire must be made of cast iron. It should be of about four inches depth, and of a conic form, converging outwards. It should have an outward rim, or margin turning off from the ring horizontally; in order to its lying on the brickwork of the furnace. The diameter of the ring must be in proportion to the size of the sublimers to be hung in it: it should be about two inches wider in the lower part than their diameters; and must diverge or inlarge itself upwards half an inch. The iron work being thus prepared, and a proper quantity of Windsor bricks, and the loom they are made of, or Sturbridge clay, as well as common bricks, and coal-ash, and common mortar, provided, the dimensions of the furnace must then be thus settled.
Take the diameter of the greatest sublimer intended to be worked in it, and add to it two inches to allow for the lute, if any should be used round it; then add twenty-two inches, and it will give the diameter of the whole area of the furnace.
The dimensions of the furnace being thus settled, the ground plan must be made in the following manner.
A round of bricks must be laid of the diameter of the area of the whole fabric as settled above, and the bars must be laid in the center of it, in their proper position; and a line drawn close at the back of the furthermost cross-bar, which must begin a quarter of an inch beyond the insertion of the outermost of the long bars on one side, and extend to a quarter of an inch beyond the outermost bar on the other side. From the extremity of this line, two others must be drawn, parallel to the sides of the outermost bars, and extended to the circular line which marks the area of the whole fabric. The ground plan being so marked, a cylinder of brickwork must be raised in this circle, leaving a hollow square within the lines formed as above for the area of the fire-place and ashhole. This cylinder must be carried up about eight inches; and may be built of common bricks and coal-ash mortar: but they must be laid solid, that the whole mass may not shrink when subjected to a great heat. When this cylinder of brickwork is raised, the bars of the fire place must be laid over the innermost part of the vacuity left for the ash-hole; and the door, with its frame, must be also placed in their proper position, in the front of the bars: which will not be, in this manner of construction, on a level with the exterior surface or front of the furnace, as in those of the common kind, but only half the length of the bars from the center of the whole furnaces. The brickwork must be then again carried up six inches higher, in the same manner as before; only it must be made to take proper hold both of the cross-bars of the fire-grate and the frame of the door: but, in this part of the fabric, the courses next the fire should be of Windsor bricks; and laid in Windsor loom, or Sturbridge clay.
The fabric being raised to this height, the iron plate prepared for that purpose must be laid over the opening of the brickwork, from the top of the door frame to the exterior surface of the fabrick: that the brickwork may be carried intirely round above: and the cylinder of brick must be again proceeded with as before; only it must be now continued intirely round, forming only an area in the middle; which must be made sloping from that which is to hold the fewel; and must inlarge itself in such manner, that, in raising the furnace eight inches higher, the diameter of the cavity may be equal to the diameter of the subliming vessel, with the addition of fix inches, to allow for the space in which the fire must come round it on each side.
In the last course of bricks which raise the fabric to this height, the whole must be left for fixing the frame that is to form the opening for feeding the fire; which must be accordingly placed in it, in such manner, that the slope formed by the upper plates, which compose it, may incline towards the fire. The proper situation for this hole is in the front of the furnace, over the opening leading to the door of the ash-hole.
From this height the brickwork must be carried up, forming a hollow cylinder, for four inches more; when a course of bricks, of which the inner ends are cut sloping, must be laid so as to contract the circle of brickwork to the diameter of the iron ring for supporting the sublimer; which must be then let into this opening left at the top of the furnace, and fixed with fire-lute; the bricks surrounding it being well pointed with the same. This part of the furnace, from the fire-place to the top, should be intirely built of Windsor bricks, laid with Windsor loom or Sturbridge clay.
In the last course of bricks must be left an opening of four inches length, for venting the smoke into the chimney: over which opening, an iron plate must be laid, and carefully pointed with fire-lute; that the air may have no access to spoil the draught. The chimney may be about sixteen or eighteen feet high; and the hollow about fix inches square, or of an area equal to that; and need not be built of a greater thickness of bricks than is necessary in order to its supporting itself.
The furnace for subliming King’s yellow must have a sand-pot; as the heat of the naked fire would be too great. This pot may be of a greater or less size, according to the quantity of the King’s yellow proposed to be made: but, where there is no particular convenience in varying from it, the ordinary size will be found most commodious.
The sand-pot being procured, as likewise the rest of the iron work, according to the preceding directions given for the furnace for vermilion, except the iron ring for the top of the furnace, which in this case must be changed for a flat rim of cast iron of four inches breadth, with a groove to receive the pot, and support it hanging in the furnace, the plan of the furnace must be made out in the following manner. The diameter of the pot being first taken, six inches must be added to it, for the cavity to admit the fire to come round the pot, and the length of two bricks to allow for the thickness of the sides of the furnace: these being put together give the diameter of the whole furnace. To find the due height, the depth of the pot must be first taken; to which must be added ten inches for the distance betwixt the pot and the bars; eight inches for the distance of the bars from the ground, with the height of a brick, for a course that must be carried round the edge of the pot; which, being all put together, give the height. The building may be then carried on, in the same manner as was before advised for the furnace for vermilion, till all be completed but the last course; and the rim must be then laid on the top of the brickwork, and well pointed with fire-lute: after which, when these parts of the furnace are so dried as to hold well together, the pot should be let down into the furnace, where it will hang by its margin or turned edge, resting on the groove made for it in the iron rim: and another course of bricks must then be raised, in a continued line with the sides of the sand-pot, that part of them which touches the pot being laid in fire-lute.
The furnace for calcining the Prussian blue, oker, ultramarine, &c. may be constructed in the following manner. First prepare a set of bars, which may be a foot in length, and sixteen in number, with a strong frame and door of which the breadth must equal that of the bars, and the height be a foot, as also a plate, or two strong flat bars, to support the brickwork over the door frame, and another to support the brickwork over the ash-hole. A foundation or pedestal of bricks must then be raised, about three feet and a half high, and two feet four inches square; which may be done with common bricks and mortar; and need only, indeed, be four walls; the hollow formed by which may be filled up with rubbish, and floored over with bricks or tiles. On this pedestal, raise three other walls; one on each side, and one at the furthermost end, of the whole brick thickness, forming an area betwixt them, of the length of a foot, and of the breadth of ten inches; of which area the front will necessarily be open from the default of the fourth wall. Over this opening, in the front, lay the bars in the center of the brickwork; and place along with them a plate, that will reach from their edge to the extremity of the furnace, to bear the brickwork which must lie over that part of the hollow. Then carry up the sides as before, but with four walls instead of three, to inclose the area of the fireplace intirely; taking care, that the first course have good hold of the flat ends of the crossbars.
This part must rise eight inches above the bars: and then the door and frame must be fixed; and the other sides carried up as before.
When the building is carried to the height of the door and frame, the strong plate must be laid to bear the brickwork over it: and the hollow must then be made to converge, till it become so narrow as to form a chimney: of which the area of the cavity may be fix inches square; or it may be turned into a funnel, or flew, to communicate with any other chimney, if such there be sufficiently near. But, as the wind-furnace demands a very considerable draught, if the flew be made from it into the chimney of any other furnace, which may not happen to be at work when there is occasion to use this, care must be taken to stop the chimney of the other furnace, below the admission of this flew into it, to prevent a false draught which would otherwise intirely destroy its effects on the wind-furnace: and for this end, registers should be always put to the flews, or chimneys below where the flews enter, of each furnace, whenever two or more vent themselves into the same common funnel.
Sublimers must be of glass, and may be generally had ready made of a proper figure at the glass-houses, where glasses are blown for the common chemical purposes. They must be inquired for under the name of bodies, or cucurbits; which name they bear when applied to medicinal uses. They should be chosen of a spheroidal form; neither the conical shape in which some, nor the oval in which others are made, being so commodious for subliming colours, as a longish spheroid: but, where they cannot be obtained of this figure, an oval may be dispensed with.
The magnitude of the sublimers must be determined by the quantity of matter to be sublimed; and the dimensions of the furnace: but those used in sand-pots should be always at least two inches less in the diameter than the pot in which they are to be placed: and those used in the naked fire should never be more than four inches less in diameter than the iron ring of the furnace in which they are to be hung.
Where vermilion is made in great quantities, earthen sublimers are used; but we shall speak of them in their proper place.
A pewter boiler is necessary for boiling cochineal, brazil or other woods, French berries, &c, for making lake, brown pink, Prussian blue, and many other pigments. It is requisite that this metal should be used for it, be cause iron and copper, as they will necessarily be corroded in a greater or less degree by the saline substances requisite to be used for making several sorts, are extremely injurious to the colours; and should, therefore, never be suffered to approach the finer kinds.
The form of this boiler may be cylindrical, with a bottom making a section of a sphere. Its dimensions may be three feet in depth, and one diameter: but this may be varied, as the quantities of colours proposed to be made may vary the occasion. At the height of about two feet, must be joined to it, a strong margin or rim, by which it may be hung in the furnace; and a little above, must be two bow handles opposite to each other, by which it may be lifted in and out of the furnace. The whole must be wrought strong; as there will be frequent occasion to move it, when containing a considerable quantity of fluid.
The furnace for this boiler must be constructed in the following manner.
A rim of iron, such as was before directed to be used for hanging the sand-pot, together with the other iron-work, must be first procured. The diameter of the boiler being taken, as also its depth below the rim by which it is to hang, the proceeding in the fabrication may be the same as that of the furnace for the sand-pot, till the iron rim is to be fixed; when the course of bricks, which is raised upon the rim in that kind of furnace, must be in this wholly omitted. It is not improper, however, to allow two inches more distance, in this furnace, betwixt the boiler and the fire, than was directed for the sand-pot: because the boiler may otherwise be more liable to be melted on any negligent treatment. When the boiler is used, it is to be lifted into the furnace; and hang by the rim, which must rest in the groove made for that purpose, in the iron rim; and, if it is to be emptied while the furnace is hot, it should always be lifted out with two or three gallons of fluid remaining in it: otherwise the bottom will be melted by the heat of the furnace: and, as the round figure of the bottom renders it not proper for standing of itself, on the flat ground, a bass-work hassock or cushion should be made, sinking in the middle correspondently to the form of the bottom of the boiler.
A pewter-bowl, with a handle of proper length, should be had to this boiler, for lading out any matter boiled in it; as likewise an instrument of the same metal, made like a poker, but with a flatter end, for stirring about any solid matter that may be put along with fluids into the boiler.
Retorts are useful for some purposes in the making colours; and glass receivers of various sizes for many. They may both be of the form in which they are usually found ready made at the shops and glass-houses: but it is proper to have some receivers very large; and with necks so wide, that the hand may be introduced into them to clean them thoroughly.
A balneum mariæ, or evaporating bath is likewise necessary. It may be made by fitting a tin boiler formed like the pewter one to the above described furnace: but it need only be a foot in depth below the rim for hanging it in the furnace; and only one inch in height above. To which boiler, a pewter vessel for containing the matter to be evaporated, must be adapted. It must be at least two inches less in diameter than the boiler; and must have a rim like that of the boiler, by which it may rest on the edge of the boiler, hanging in the cavity.
Proper filters are extremely requisite for the preparation of many pigments. They should be made of pewter, in the form of the common earthen cullenders; and their size should be such as admits of their interior surface being wholly covered by a sheet of filtering paper, when laid into them. Their edge should be turned outwards, so as to form a margin or rim, by which they may hang on a proper frame, over the tubs, or other vessels, which are to receive the liquid they filter: and this frame may be only two narrow pieces of wood, of sufficient strength to bear the weight of the filter and its contents, fixed together by two other cross pieces, at such distance, that the filter may just pass betwixt the four, and hang by the rim. For these filters, must be provided, proper paper; as also linnen cloths, to lay over, or under, the paper occasionally. The kind of paper fit for this purpose is that called bloom or filtering paper: but care must be taken in the choice of it; for it is difficult to find, in common stationers shops, such as will even moderately well answer the end.
For coarse colours, such as rose pink, flannel bags may be employed, for expedition. They should be made in the form of pudding bags; and are called, when applied to this purpose in medicine, Hippocrates’s sleeve. They should have proper frames for fixing them; which may be made of three sticks or wooden rods, fixed together at such a distance, that the bag, being hung upon them by three loops fastned to it, may have its mouth or opening subtended to a due width for pouring in the matter to be filtered.
Long boards must be likewise provided for drying colours. They should be made of found wood; and very well plained, and it will be yet better, if the surface be made still smoother, by varnishing them with seed lac.
Chalk-stones are also proper on some occasions, for expedition, for the drying ultramarine, Prussian blue, washed okers, and several other kinds: but they must never be used for lake, carmine, or any colours made of vegetable matter; for their alkaline quality of chalk may be very detrimental to such colours. Where Prussian blue is made in very great quantities, there is a particular apparatus used for drying it: but we shall speak of that in its proper place.
The levigation of colours, being of the most general use of any operation, is likewise required in many cases to be most perfectly performed; and, therefore, proper instruments subservient to it are extremely requisite. Handmills, and sometimes even horse-mills, are used for grosser sorts of pigments, or where very large quantities are to be dispatched: but, as they are to be had of the proper workmen, duly constructed, it is needless to describe them here. The muller and stone are generally useful; and should alone be depended on, at least for completing the levigation after the grinding them in the mills, whenever the colours are of any greater value or nicer use. Basons should likewise be provided for washing over the colours according to the manner below described.
pp. 29–42
SECTION III.
Of the general operations subservient to the making or preparing colours.
THE operations subservient to the making and preparing colours are sublimation, – calcination, solution, – precipitation, – filtration, – and levigation.
As the practice of most of these operations is confined at present, in a great degree, to the purposes of chemistry; and therefore, very little understood by any, except those who concern themselves in that art, I shall endeavour to explain them, as far as they relate to the preparation and treatment of colours; and to give such general directions for the performing them, as may take away the necessity of repeating, on every occasion, those particulars, which occur in almost all the processes that partake of the same nature: but with respect to such operations, as are more commonly known and practised, I shall only touch on them, in a more general way, without entering into minuter considerations regarding them.
pp. 30–33
Of sublimation.
Sublimation is the raising solid bodies in fumes, by means of heat: which fumes are afterwards collected by condensation, either in the upper part of the same vessel where they are raised, or in others properly adapted to it for that purpose.
The end of sublimation is, either to separate substances from each other in order to the purification of one of them, or to mix them more perfectly than can be effected, without subjecting them to such a degree of heat as will necessarily render them volatile.
The means are, to put the matter, whether simple or compound, into a proper vessel or sublimer, and there give it a due heat, by placing it in a sand-pot, or the cavity of some furnace where the naked fire is required: in doing which the following particulars are the most material objects of attention.
The first care must be to provide glasses of the kind above mentioned, p. 24, and of a due size, which must be regulated as was before mentioned by the quantity of matter to be sublimed, and by the dimensions of the sand-pot, or cavity of the furnace where they are to be used.
The sublimer used for making King’s yellow, or for any other operation to be performed in a sand-pot, need no previous preparation. But those to be used for vermilion, which must be placed in the naked fire, should be first well coated with the fire-lute; and a rim of the same matter must be worked round the coat at about two thirds of the height of the sublimer, to support it in the iron ring when let down into the cavity of the furnace. This coat of lute should be laid on of such thickness, that it may be about half an inch thick when thoroughly dry: and, if it be laid on at several distances of time, so that the first covering of the glass may be pretty dry before the second be put on, it will be the better; but great care should be taken, that the whole be of sufficient dryness before the sublimer be let down into the furnace; and that the rim of lute fit well the iron rim; for otherwise ill success will most likely attend the process of the operation. In default of the fire-lute the following may be substituted in its place, for the coating sublimers; and is indeed, on account of its cheapness, most commonly used; though greatly inferior to the other with respect to the security of the glasses.
“Take of Windsor loom, or, if very good, common loom, fine Sand, and dung of horses which feed on hay, each equal parts. Temper them, with water, or the blood of any beast; and beat them well together.”
In fixing the sublimers in the sand-pots, an inch and half, or two inches of sand, must be first put into the pot; on which the sublime must be gently set. The pot must then be filled with sand up to the brim; and the matter to be sublimed must be put into the sublimer, through its neck or mouth; which must be afterwards covered by a piece of tile, or flat glass, laid loosely upon it.
The sublimers used without a sand-pot must be fixed, in the cavity of the furnace, by letting them through the ring of iron on the top of the furnace, till they hang by the rim of lute. After which the joint formed by the rim and ring must be made good by pointing with the fire-lute; which must, however, be of dryish consistence; and used sparingly, left it moisten the lute of which the rim is made, and, causing it to give way, occasion the sublimer to slip through, and fall into the furnace.
The sublimers being fixed the fire must be lighted; but must be kept in a moderate degree till the lute be thoroughly baked; when, being increased, the matter will rise in fumes; and form itself, in a cake, on the upper part of the glass: and this may be urged forwards by raising the fire, as strongly as it will bear to be without forcing the fumes out of the mouth of the sublimer: which, if it appear to happen, must be remedied as quickly as possible by abating the heat; but proper care must be taken, that the mouth of the glass or sublimer be not choaked up by the subliming matter; for which reason, the tile, or piece of glass, which covers it, should be lifted up at proper intervals, and an opening made, with the end of a tobacco-pipe, into the cavity of the sublimer. On the neglect of this caution, the glasses are very liable to be burst, by the rarefaction of the fumes, on the fires burning briskly. When no more fumes arise, which may be known by the abatement of the heat in the upper part of the sublimer notwithstanding the fire be equally strong, the operation may be concluded to be completed; and, the furnace being suffered to cool, the sublimer must be taken out, and broken; and the cake of sublimed matter in the upper part of the glass collected: observing carefully, that it be kept free from the dross or caput mortuum left in the bottom.
Of calcination.
Calcination is the operating on substances, by means of heat, so as to produce some change either in their texture or colour.
Calcination is sometimes performed, by exposing substances to the fire with as great extent of surface as possible: as in the case of lead for converting it into the red lead or minium, and antimony to prepare it for its conversion into glass: in other cases, it is performed, by putting the substances into a crucible, or other such vessel, in a more collected body; and surrounding the vessel with fire: and there is a case indeed, viz. that of the masticot, where bringing it near the fire will be sufficient.
The red lead, red oker, and antimony for making the glass, being calcined in large quantities by those, who make it their sole business, and have large furnaces like ovens constructed for these particular purposes, I shall be less explicit with regard to them; as it will be scarcely worth while for any, but those who carry it on as a gross manufacture, to concern themselves with them, unless as a speculative experiment.
The calcinatien of other substances for the preparation of colours may be performed, by putting the matter into a crucible, and placing it in a common fire; or, where greater heat or room is required, in the wind-furnace described p. 22 where the fire must be raised round it; and continued of such a degree, and for such a duration, as the occasion may make necessary.
This may be understood to be all that is requisite, where calcination is ordered, in the processes below given, without any particular direction for the manner of performing it: but where such direction is needful, it will be found to be inserted as each occasion occurs.
Of solution.
By solution is meant, the reducing any solid body to a liquid state by means of another, into which, being put, it is melted or converted itself also into a state of fluidity.
This is performed, by the simply putting one body to the other and mixing them well together, except in some cases, where heat is necessary to expedite the effect.
When therefore bodies are ordered, in the processes below given, to be dissolved in others, it is only to be understood, that they are to be put together, and stirred, or shaken, at proper intervals, till the solid body be melted: and where that appears to proceed too slowly, the vessel must be put into a proper heat to accelerate the operation: but this heat should be always understood to be less than will make water boil, except where the contrary be expressly directed.
Of precipitation.
Precipitation is the re-separating a solid body, from any fluid one in which it is dissolved or melted, by the addition of a third body, which is capable of producing that effect. As, for example, if feed-lac be dissolved in spirit of wine, and water be added, the feed-lac will be precipitated, that is separated from the spirit in which it was dissolved, and reduced to the state of an impalpable powder, which will subside to the bottom of the vessel containing the mixture.
The means of precipitation are therefore equally simple with those of solution: there being nothing more required, than to put the matter, which is to suffer the precipitation, into a proper vessel; and to add that which is to cause it; and when the effect is produced, to separate the fluid from the solid body precipitated, by pouring off what can be so parted from it; and draining off the rest in a filter.
Of filtration.
Filtration, though a very simple operation yet when it is required to be done through paper, and great quantities of fluid are to be filtered, demands some nicety and judgment in the management of it; otherwise accidents are very liable to happen, which retard greatly the work; and occasion frequently great delay and trouble; especially with those who are unpractised in it.
As the end of filtration is of two kinds, the one to free fluids from any solid bodies of a feculent nature with which they are mixed, the other to separate any precipitated powder, or other solid body, from superfluous fluid, the means must be varied. In the first case, paper, if it be of a right kind, is sufficient; in the other case, a coarse linnen cloth must be put over the paper; otherwise, in taking the filtered matter out of it, parts of the paper will unavoidably mix themselves with it, and irremediably foul it.
Where filtering through paper is necessary, the pewter cullenders described p. 24. will be found extremely commodious: but great care must be taken to accommodate rightly the paper to the cullender, as well as to pour the matter very slowly into it at first, till it be well settled, for on neglect of this caution, the paper will be very apt to burst, and delay the operation, by fouling the vessels with the unfiltered matter. If, as frequently happens, the paper, which is procured, prove of a bad texture, and want tenacity to bear the weight of the fluid poured into it, or when the fluid itself may be of a very relaxing nature, and weaken the paper, a coarse linnen cloth should be always used with the paper, whatever the intention of the filtering may be. For, though the fluid will pass faster through paper alone, yet much time will be saved from adding the linnen, by preventing the troublesome accidents that will else unavoidably occur.
In filtering large quantities, it will be frequently found, that, after the paper has been for some time soaked in the wet, the operation will proceed very slowly; the swelling of the substance of the paper, as well as the foulness of the fluid, diminishing, and at last choaking up, the percolating pores of the paper. When this is the case, the paper should be always changed as soon it is perceived, that the filter ceases to run moderately: for, otherwise, the operation becomes intolerably tedious.
Where great quantities of more ordinary colours are made, such as rose pink, the kind of Prussian blue used for paper-hangings, or other such grosser kinds, the flannel bags mentioned p. 28 may be used; as the filtering such great quantities of fluid through paper would be an almost endless labour. In doing this, nothing more is required than to hang the bags on the frames by their loops; and to feed them with the matter to be filtered: only the first quantity which runs through, being apt to be foul, must be returned into the bag, till it be perceived that the fluid come clear.
Of evaporation.
Evaporation, or the reducing moist bodies dryness by an artificial heat, where it is not required to be in balneo mariæ, may be performed by boiling in any commodious vessel, till the matter be freed from all humidity; the vessel being fed with a fresh supply as the fluid appears to be diminished: but in the case of vegetable or animal substances, where they are to be evaporated to dryness, or a thick consistence, as in the artificial gall-stones, lake or brown pink, it ought to be performed in balneo mariæ; that is, by putting the vessel containing the matter into another filled with water, and kept of a boiling heat: for, by this means, the substances are prevented from burning to the vessel as they grow dry; which would otherwise unavoidably happen.
The evaporation in balneo mariæ may be commodiously performed in the vessels I have described p. 27, by fixing the tin boiler in the furnace, and hanging the pewter vessel in it by the rim; the remaining cavity of the tin boiler, being filled with water, and made to boil till the matter be brought to a proper dryness or consistence. This is all that is requisite where the quantity of matter remaining after the evaporation is large; but, where it is small it is better to use some smaller vessel; as it would be so diffused on the sides and bottom of the pewter one as would render it difficult to be collected. The best expedient for this, is to use a China bason of a proper size; and to hang it, by packthread, to two sticks laid across the edge of the boiler, and fixed, at a proper distance from each other, by two other sticks tyed to them crossway: by which little machine, the bason may be suspended in the boiling water; and, being fed with the fluid to be evaporated as proper room appears in it for a fresh supply, will perform the office extremely well. But where the quantity of fluid to be evaporated is great, though the remaining matter when dry be small, a previous evaporation, by the naked fire, may be used till the quantity be properly reduced; taking care, that the matter do not acquire so thick a consistence, as may subject it to burn to the sides or bottom of the boiler.
Of levigation, and washing over.
Levigation of colours, where great quantities are in question, is performed in hand and horse-mills: but this fails to produce so perfect an effect, as the muller and stone, which is used in all other cases: the assistance of a pestle and mortar being indeed taken in the case of glass, and hard bodies, to prepare them for the mills or stone.
The method of using these several kinds of instruments, as well as the constructure of the instruments themselves, are so well known, that it is needless to dwell on any particulars regarding them: but the other method subservient to the intention of levigation, (that is to say to the reducing pigments to a due degree of fineness as powders) called washing over, being less generally understood, and yet of the greatest utility for procuring many colours in the most perfect state, I will explain fully the manner of performing it; which is as follows.
“The matter intended to be brought, by this operation, to an impalpable fineness, being first well levigated, or, if it be a body of a chalky texture as the okers, broken to a gross powder by pounding, let it be put into a deep bason almost full of very clean water; and there well stirred about: then, having rested a short time, that the grosser parts may sink to the bottom, let the water, together with the finer parts yet suspended in it, be poured off into another bason of the same kind; and suffered to stand at rest till the powder has totally subsided, and left the water clear. Let as much of this water, as can without disturbing the sediment, be then poured back into the first bason; and let the stirring, decantation, &c. be repeated as before, as often as shall be found necessary to separate all the powder that is of sufficient fineness. The remaining grosser part may be then again ground; and the same treatment continued, till the whole of the matter be obtained in that state. This operation is, however, in some cases, to be repeated several times before the colour can be rendered so perfectly fine as may be wished: but when it is duly executed, pigments may be reduced to the most impalpable powders, with great ease, even though, like vermilion, of the most obdurate texture: and the okers, or any such bodies of a chalky or clayey texture, which grow soft in water, may be freed from sand, stones, or other impurities, and rendered of the highest degree of fineness, even without any previous grinding. Where great quantities of matter are to be washed over, as in the case of okers, common Indian red, &c. tubs must be had to supply the place of basons; and lading with a bowl-dish must be used instead of decantation or pouring off.”
p. 42–46
SECTION IV.
Of the nature and preparation of
particular colours.
CLASS I. Of red colours.
Of vermilion.
VERMILION is a bright scarlet pigment, formed of common sulphur and quicksilver, by a chemical process: it is one of the most useful colours in every kind of painting; except enamel or glass; as it is of moderate price, spends to great advantage in any kind of work, and stands or holds its colour extremely well. It may be prepared in great perfection by the following process.
“Take of quicksilver eighteen pounds, of flowers of sulphur fix pounds: melt the sulphur in an earthen pot; and pour in the quicksilver gradually, being also gently warmed; and stir them well together, with the small end of a tobacco-pipe: but, if from the effervescence, on adding the latter quantities of the quicksilver, they take fire, extinguish it by throwing a wet cloth (which should be had ready) over the vessel. When the mass is cold, powder it, so that the several parts may be well mixed together; but it is not necessary to reduce it by nicer levigation, to an impalpable state: having then prepared an oblong glass body, or sublimer, by coating it well with fire-lute over the whole surface of the glass, and working a proper rim of the same round it, by which it may be hung in the furnace in such a manner that one half of it may be exposed to the fire in the cavity of it, fix it in a proper furnace; and let the powdered mass be put into it, so as to nearly fill the part that is within the furnace: and, a piece of broken tile being laid over the mouth of the glass, sublime then the contents, with as strong a heat as may be used without blowing the fumes of the vermilion out of the mouth of the sublimer. When the sublimation is over, which may be perceived by the abatement of the heat towards the top of the body, discontinue the fire; and, when the body is cold, take it out of the furnace; and break it: and, having collected all the parts of the sublimed cake, separating from them any dross that may have been left at the bottom of the body, as also any lighter substance than may have formed in the neck, and appears to be dissimilar to the rest, levigate the more perfect part; and, when reduced to a fine powder, it will be vermilion proper for use.”
Where great quantities of vermilion are manufactured, it is a practice, for the fake of cheapness, and to save the labour of coating, with so much care, glass sublimers with lute, to have earthen ones made of the same sort of clay as that employed for long necks. When this is done, these sublimers should be of a spheroidal figure, and about an inch less in their least diameter than the ring of the furnace in which they are to be hung; they must also have a rim worked at about two thirds of this height, of the same matter they are made of, by which they may hang in the iron ring, as the glass sublimers, by means of the rim of lute. It is much the best way, however, to give them a coat of good common loom, sand and horse dung.
The perfection of vermilion is to be of a very bright colour, and of a great degree of fineness, and that is most esteemed, which most inclines to a crimson hue: these appearances, besides the rendering it more advantageous for the purposes to which it is employed in painting, are the readiest proofs of its being unsophisticate.
Vermilion, when pure, will stand for any length of time, whatever vehicle it be used with; and may, therefore, be depended upon, for carnations, or the nicest purposes.
It is very usual, I might almost say general, for dealers to sophisticate vermilion with red lead: which renders it very liable to change, and lose its brightness; as the red lead is apt to turn black, whether used with oil, or water. This adulteration, when made in a greater degree, may be perceived by the difference in colour betwixt the sophisticated and pure; for the red lead, being considerably more of the orange hue than the vermilion, renders it less crimson. But to detect the fraud of mixing red lead with the vermilion with certainty, both with respect to the general fact, and the proportion, the following means may be used.
“Take a small, but known quantity of the vermilion suspected to be adulterated, and put it into a crucible; having first mixt with it about the same quantity, in bulk, of charcoal dust: put the crucible into a common fire, having first covered it with a lesser crucible inverted into it; and give a heat sufficient to fuse lead; when the crucible, being taken out of the fire, should be well shaken, by striking it against the ground. If the suspected adulteration have been practised, the lead will be found reduced to its metalline state, in the bottom of the crucible; and, being weighed, and compared with the quantity of cinnabar that was put into the crucible, the proportion of the adulteration may be thence certainly known: but, if no lead be found in the crucible, it may be safely inferred, that no red lead had been commixt with the cinnabar.”
It is very necessary, that vermilion should be extremely well levigated: as it both contributes to its brightness and spending further in the work: and this can scarcely be effectuated by mills without the subsequent use of th mullar and stone; though it has been usual for preparers to pass it off as it comes out of the mill: but whoever would have vermilion in perfection, especially for painting carnations or mixing with white, should improve its fineness by washing over.
pp. 46–47
Of native cinnabar.
Native cinnabar is a pigment compounded of quicksilver and sulphur; and therefore differs in nothing from vermilion but in the manner of its production, and the being sometimes of a more crimson colour. It is found naturally formed in the earth in many places; but seldom so pure as to be fit for the uses of painting, at least without being purified by sublimation; which operation, being probably not well known to those who have any concern in the finding it, has not been hitherto practised, as far as appears. On this account native cinnabar has as yet been scarce and dear: a great part of what has been fold as such, having been factitious: but the crimson colour of some quantities, and the mistaken notion that it would stand better than vermilion, because it was a natural production, have made it to be coveted by painters who are curious in colours. It is however never worth their while to be sollicitous about it, as it seldom excels the best vermilion in brightness; and as that may be likewise rendered equally crimson, if the proportion of sulphur be made only as one to six or seven of the quicksilver: and as, if there really was any superiority, with regard to standing, in the native cinnabar over the other, they never could be certain of having it genuine.
When native cinnabar is used as a colour, there is no other preparation necessary than a careful levigation; which may be best performed, with water, on the stone: but whoever would have it in the most perfect state must superadd washing over to the grinding. It has been usual to wash this colour as well as vermilion in urine, juice of lemon, and other fluid substances; but there is not the least alteration to be made in it, by any such means, if it be pure, for the reason before given with respect to vermilion.
. . .
pp. 49–50
Of Scarlet oker.
Scarlet oker, is the ochrous earth, or rather iron, which is the basis of green vitriol, separated from the acid of the vitriol, by calcination. It is of a broken orange scarlet colour: but, for its great certainty of standing, in which it equals any of the native okers, and its extreme great strength and warmth either as a ground or in the shades of carnations, it is nevertheless very valuable. It may be used as a colour in any kind of painting; (but in enamel it turns to a transparent yellow like brown pink, if the flux be strong): and is easily prepared in the following manner.
“Take, of green vitriol or copperas, any quantity: and being put into a crucible, of which it will fill two thirds, set it on a common fire to boil,(taking care that it do not boil over,) till the matter be nearly dry; when it will be greatly diminished. Fill then the crucible to the same height again, and repeat this, till the crucible be filled with dry matter. Take it then from this fire, and put it into the wind-furnace; or, if the quantity be small, it may be continued in the same fire, the coals being heaped up round it; and let the contents be calcined there till they become of a red colour when cold; which must be examined by taking a little of the matter out of the middle, and suffering it to cool: for so long as it remains hot the red colour will not appear, though it be sufficiently calcined. When duly calcined take the oker out of the crucible while hot, and put it into water, in which the parts of the broken crucible may be soaked likewise to obtain more easily what shall adhere to them; and stir the oker well about in the water, that all the remaining vitriol may be melted out of it. Let it then settle, and when the water appears clear, pour it off, and add a fresh quantity; taking out all the broken pieces of the crucible; and proceed as before; repeating several times this treatment with fresh quantities of water. Then purify the oker from any remaining foulness by washing over; and, having brought it to a proper state of dryness, by draining off the fluid by a filter, in doing which the paper used must be covered with a linnen cloth, lay it to dry on boards.”
pp. 50–51
Common Indian red.
The common Indian red, meant here, is of an hue verging to the scarlet: but the true Indian red, (of which I shall speak below) is greatly inclining to the purple: among which colours it may be well classed.
This common kind has been introduced as a counterfeit or substitute for the real kind brought from the East-Indies: and has, by its cheapness and serving equally well for common purposes, prevented that from being brought over for a long time. So that the true teint of the original kind, being in some measure forgotten, this has been gradually made to vary from it, till it is in fact a quite different colour. But though the common Indian red will not answer the ends of the true kind, it is yet a very useful colour for many other purposes: and is, therefore, on account of its standing and warm though not bright colour, much used as well in finer as coarser paintings in oil. As it is made of the caput mortuum of vitriol after the distillation of aqua fortis and oil of vitriol, it is afforded at a very moderate price, and may be thus managed.
“Take, of the caput mortuum or oker left in the iron pots after the distillation of aqua fortis from nitre and vitriol, two parts, and of the caput mortuum or colcothar left in the long necks after the distillation of oil of vitriol one part; break the lumps found among them and put them into tubs with a good quantity of water; and, having let them stand for a day or two, frequently stirring them well about, lade off as much water as can be got clear from them; and add a fresh quantity, repeating the same treatment till all the salts be washed out, and the water come off nearly insipid. The red powder which remains must then bewashed over, and being freed from the water laid out to dry.
When this is designed for nicer purposes, it should be washed over again in basons, the gross manner of lading it out of one tub into another not fitting it always completely to such ends.”
p. 52
Of Venetian red.
Venetian red is a native red oker, rather inclining to the scarlet than the crimson hue: it is not far different from the common Indian red, but fouler; and may, therefore, be easily prepared from mixing common red oker with the colcothar or caput mortuum taken out of the aqua fortis pots, and washed over.
As it is generally used by house-painters in imitations of mahogony, it requires no other preparation than to be well ground with the oil with which it is used: but when, as is sometimes the case, it is used in miniature painting, it should be carefully washed over.
pp. 52–53
Spanish brown.
Spanish brown, or brown red, is a native earth, found in the state, and of the colour in which it is used: it is nearly of the same colour with the Venetian red, but fouler. It was probably from its name brought originally from abroad, and was then most likely of a finer kind: but what is now used is the produce of our own country, being dug up in several parts of England.
It is used for grounds and primings for coarse work by house-painters; and by colourmen in the preparation of the cloths for pictures and other coarse work: but seldom in any more delicate paintings. It therefore needs no other preparation than freeing it well from stones and filth: tho’ if any who may be desirous to use it for nicer purposes, want to have it in a more perfect state, they may make it equal, in fineness and purity to any other pigments whatever, by washing over: and, if they can render it useful to them with regard to the colour, they may depend on its standing equally with any other pigment whatever; being a native ochrous earth, of which kind none are ever known to fail, whether they be used of their natural teint, or changed by calcination.
pp. 53–54
Of calcined or burnt terra de Siena.
The terra de Siena is a native oker brought hither from Italy in the state it is naturally found: it is yellow originally; (of its qualities in which state we shall treat in its proper place below;) but when moderately calcined, it becomes an orange red, though not very bright. Being, however, semi-transparent in oil, it is of great use where a strong brown red shade is wanted; as in the face in portrail painting, and on many other occasions.
The calcination may be performed by putting lumps of it, either in a crucible, or naked, in a common fire: and continuing it there, till the colour be changed from yellow to red in the proportion wanted; after which, it must be well levigated and washed over.
With respect to the goodness of terra de Siena, we have but one kind brought here: and whoever can obtain it crude, in the unburnt lumps, may be certain it is not adulterated.
. . .
p. 66
Red oker.
Red oker is a native earth: but what is commonly used is made red by calcination: being when dug out of the earth yellow, and the same with the yellow oker commonly used. It is chiefly brought from Oxfordshire, where it is found in great plenty, and burnt in large ovens. The quality it has, in common with all other okers, of standing infallibly, renders it very useful, as well in the more delicate as coarser paintings in oil, notwithstanding it is not bright: but in order to its being fit for nicer purposes, it ought to be washed over; though for others, it may be used in the state in which it is found in the shops.
The cheapness of red oker renders it scarcely worth while to adulterate it: but, either from such practices, or from the difference of their natural state, some parcels are greatly better than others. The marks of goodness are brightness of colour; and the being of a crumbly chalky texture, shewing no gritty roughness when rubbed betwixt the fingers.
pp. 67–73
CLASS II. Of blue colours.
Of ultramarine.
ULTRAMARINE is a preparation of calcined lapis lazuli. It is, when perfect, an extreme bright blue colour, with a transparent effect in oil, and in some degree in water; and will stand, when used in painting, without the least hazard of flying, with whatever vehicle, or pigment, it be mixed. For these reasons, ultramarine is of the highest value in every kind of painting; being equally serviceable in all, even in enamel: and though the invention of Prussian blue, on account of its much lower price, has greatly lessened the use of it, yet this exclusion of it may be considered as an injury to painting in general; as the skies of landschapes, and many other parts of modern pictures, shew the loss of it, by their changing from a warm, or clear blue, to a faint greenish or olave teint.
There have been a great variety of methods taught, and practised, for preparing the ultramarine. The older methods were, after a calcination in a crucible, to mix a composition of pitch, resin, Burgundy pitch, sope, wax, and other ingredients; and to form a paste of them with the calcined matter; which paste was then put into water for several days; and afterwards dissolved, by successive quantities of warm water poured on it, till it let go the colour of the calcined ultramarine; which was recovered by the same means as is directed for the washing over colours in p. 40. But this method of employing a variety of ingredients, in the cement, was not only unnecessary, but injurious to the colour; which was never perfectly freed by the warm water from them: and for this reason, the methods have been continually varied by those, who have attempted to prepare this pigment. I shall however give the best of the more modern; and subjoin one of older date; which I believe, nevertheless, to be equally good, though not near so troublesome.
“Take the lapis lazuli, and break it into very small pieces, or rather a gross powder. Put it into a crucible; and cover it securely to prevent the coals from falling amongst it. Calcine it then, with a strong fire, for an hour if there be any large quantity, or less time in proportion; and quench it, when taken out of the fire, in vinegar; stirring them well together; and suffer it to remain in that state for a day or two. Pour off then the vinegar; except what may be necessary for moistning the calcined lapis lazuli in grinding; which operation it must then undergo, in a mortar of flint or glass, till reduced to the greatest degree of fineness those means may effect; but, if it appear yet too hard to be easily ground, give it another short calcination; and quench it a second time in vinegar. The vinegar must then be washed off from the powder, by the putting to it several successive quantities of clean water; each of which must be poured off when the lapis lazuli has been well stirred about in them, and is again settled to the bottom. It must then be ground on a porphyry stone, with a muller, till it be perfectly impalpable; and then dried: in which state it is duly prepared to mix with the following cement. – Take of Burgundy pitch, nine ounces, – of white resin, – and Venice turpentine, six ounces, – of virgin wax one ounce and half, – and of linseed oil one ounce and a quarter. Mix them together by melting in a pipkin over the fire; and suffer them to boil till they acquire so stiff a consistence, that, being dropt into water while of this boiling heat, they will not spread on the surface of it, but form a roundish mass or lumps. The cement being thus formed, may be poured out of the pipkin into the water: and made into cakes or rolls for use. Of this cement, take an equal weight with that of the calcined lapis lazuli; and melt it in a glazed earthen pipkin; but not so as to render it too fluid. Then add to it the calcined matter by very slow degrees; stirring them together with an ivory spatula till the whole appear perfectly mixed. Being thus mixed, heat the composition to a something greater degree, and cast it into a large bason full of cold water: and, when it has cooled to a consistence to bear such treatment, knead it well like the dough of bread, with the hands rubbed over with linseed oil, till all the parts be thoroughly incorporated with each other: then make the mass into a cake; which may be either kept till some other convenient time in cold water, or immediately proceeded with in the following manner. Put the cake into an earthen dish or bason; the bottom of which should be rubbed with linseed oil, and pour on it water of the warmth of blood: let it stand a quarter of an hour; and, as the water softens the cake, it will let loose the finest part of the calcined matter: which, on gently stirring the water, but without breaking the cake or separating it into lesser parts, will be suspended in the water; and must be poured of with it into another vessel. The quantity of water must be then renewed: and the same operation repeated a second or third time: and, as the mass appears slack, in affording the colour, it must be moved and stirred, in the manner of kneading, with the ivory spatula, but not broken into fragments or small parts: and, when so much of the colour is extracted, as to render it necessary for the obtaining more, the heat of the water must be encreased to the greatest degree. The quantities of the calcined matter, (which is now the lapis lazuli,) that were first washed off, and appear of the fame degree of deepness and brightness, may be put together: and the same of those of the second degree; the last washings making a third. The water being then poured off from each of these parcels, put on a lixivium formed of two ounces of salt of tartar, or pearl- ashes, dissolved in a pint of water, and filtered thro’ paper after the solution is cold: which lixivium must be put on boiling hot, and the lapis lazuli stirred well about in it; and then the mixture set to cool. The powder being subsided, the clear lixivium must be poured off, and clean water put in its place: which must be repeated till the whole of the salts of the lixivium are washed away. The lapis lazuli must afterwards be dried; and will be then duly prepared for use.
Another method of purifying the ultramarine from the cement may be used; which is, the pricking the yolks of eggs with a pin, and moistning the matter to be purified with the soft part that will run out, and working them together in a glass or flint mortar: after which the mixture must be put into the lixivium; and proceed with as is above directed.
In order to free the ultramarine from that part of the water, which cannot be poured off from it without carrying away part of the powder, let it be put in a deep pot, such as the cups made for coffee; and, after the whole is poured off that can be without loss, set the pot so on a table or stand, that strings put into it may hang below the bottom; and then take three or four thick threads of loose twisted cotton; and, having wet them, put one end of each into the fluid; and let the other, being brought over the edge of the pot, hang three or four inches below the bottom of it: by which means, the water, being attracted by the threads, will drop from the lower end till the whole be nearly drained away. The matter may then be poured upon a porphyry, or polished marble; and suffered to dry.”
The other method, I have proposed to give, differs, from the above, only in the using virgins wax and the best white resin, melted together in equal quantities, instead of the more compound cement: and this gives up the colour, on its being infused in warm water, much sooner than the other.
The other methods of preparing ultramarine differ chiefly in the manner of separating the colour from the cement and feculencies: which some recommend to be done, by squeezing and working the mass with the hand in warm water, after it has lain in it some time to soften. Others advise the putting the mass in the form of a flat cake, on a board, in a situation somewhat declining from an horizontal position, and making water drop on the board above the cake, that it may flow through it, and wash out the ultramarine: to facilitate which, the parts of the cake must be frequently opened and stirred with a stick. But this method is more troublesome and less efficacious than that above given.
Ultramarine may be also prepared, without any cement, by calcining it; and, when levigated and washed over, soaking it in distilled vinegar made hot. The ultramarine will, in this way of preparation, be produced in greater quantity; but it will be lighter coloured than when refined by the cement. It is, however, a very good method of preparing it for the skies, and some other uses.
As it is of the last consequence to the producing fine ultramarine, that the lapis lazuli, of which it is made, should be good, it may be judged of by inspection from the deepness and clearness of its blue colour; and in order to be more certain of its value, it is proper to heat a small piece red hot; which, if it retain afterwards its hardness and colour, may be accounted good, but if it become crumbly and turn brown, or appear to have specks of dulness, it may then be justly suspected, or rather condemned.
The different parcels of ultramarine produced from the same parcel of lapis lazuli, according to the above process, will differ greatly in their value: the manner of judging of which must be by the degree of brightness and deepness of the colour; but there is no being precisely certain of the worth of any but by comparing it with a specimen of known value; and to do that with great accuracy, a little of each should be thinly rubbed on white paper, or mixed with white flake and oil, by means of a pallet knife, so as to form light teints of the same degree; where the brightness will shew itself more distinguishably than in darker.
pp. 74–77
Of ultramarine ashes.
The pigment called ultramarine ashes is the residuum or remains of the lapis lazuli after the ultramarine has been extracted from it by the above given, or any similar process. But as the coloured particles which remain are mixt with those of another kind contained in the lapis lazuli, whether earths or metalline substances, these ashes must of course be much less valuable than even the worst ultramarine: sometimes, nevertheless, when the operation of the extracting the colour from the calcined lapis lazuli has not succeeded well, a considerable share of the ultramarine is left behind with the recrement, and greatly enhances the worth of the ashes: and indeed, as it is certain, that what colour they possess when genuine will never fly, they always bear a good price. The appearance of these ashes is that of ultramarine a little tinged with red, and mixed with white: but they are frequently adulterated; and made by the sophistication to look better than they would in a genuine state. This adulteration renders them much less certain of standing, if, as is most frequently the case, it be made by precipitated copper, in the manner before mentioned in the case of the adulteration of the ultramarine. This is easily, however, detected by the method above given of putting some of it into a small quantity of spirit of nitre, which, if there be any copper in it will be tinged green. But there is another means of sophistication, that will not render the colour liable to fly and indeed it is well it is so, because the difficulty of distinguishing it, when not in a high degree, is much greater. This is, the commixing, with the ultramarine ashes, smalt ground and washed over: which, when good, and thus treated, has so much the appearance of the other, that it is scarcely possible to perceive any difference by inspection.
The smalt nevertheless, however well ground, will never mix kindly with oil; but fall from it if much moistned, or with less oil forms a pasty matter: nor will it spread when mixed with white and oil, in any proportion like the ultramarine ashes. By these properties, therefore, suspected quantities may be best judged of: as the adulteration becomes apparent; if the quantity of the smalt commixed with the true ashes render them predominant.
The method of preparing the ultramarine ashes is as follows.
“Take the cement of the ultramarine, which remains after the colour is extracted; and mix it with four times its weight of linseed oil. Let the mixture be set in a glazed pipkin over the fire; and, when it is thus boiled a short time, put it into a glass vessel, sufficiently large to contain it, of a cylindrical figure: of which vessel the diameter must be small in proportion to the length. But care must be taken, that the matter when put into this glass be cool enough not to endanger the breaking it. This glass must then be put into a balneum mariæ; which must be made as hot as possible without boiling; and kept there till the colour appear to be all subsided to the bottom. The oil must then be poured off till the colour appear to rise with it; and the remainder, with the colour in it, must be put into another glass of the same kind with as much fresh oil as will rise five or six inches above the colour. This glass must be treated in the same manner as the first: and, when the colour has subsided, the oil must be poured off, and a fresh quantity put in its place. This having been likewise poured off, the colour must then be well washed, to free it from the remaining oil, first in boiling water, and afterwards in some of the lixivium abovementioned made boiling hot also. As much of the lixivium being poured off, when the colour has subsided, as can be separated from it that way, the colour must be thoroughly freed from the remainder by frequent ablutions with clean water. After which the water must be taken off by the means above directed for the ultramarine, till the matter be of a proper degree of moisture for grinding. It must then be thoroughly well ground on a porphyry; and washed over; that all the harder and insufficiently calcined parts may be reduced to an impalpable powder: in order to which, the remaining grosser parts, after the finer have been separated by the washing over, must be again ground till the whole be perfectly fine. The same means must be afterwards used to bring the ashes to a dry powder that were before directed for the ultramarine.”
. . .
pp. 88–89
Of smalt.
Smalt is glass coloured with zaffer, and ground only to a very gross powder. Its texture does not permit it to be worked with either brush or pencil; but it is used for some purposes, by strewing it on any ground of oil-paint while wet; where it makes a bright warm blue shining surface, proper for large sun-dials, and other such applications.
It is prepared from fluxing zaffer with glass of salts: the proportion of which may be one seventh part, or more or less according to the degree of deepness required in the smalt.
The goodness of smalt consists in its being dark bright and cool, though it always verges on the purple.
CLASS III. Of yellow colours.
. . .
pp. 91–93
Of Naples yellow.
Naples yellow is a warm yellow pigment rather inclining to orange, but in a very minute degree. It is seldom used but in painting with oil: where it is generally found to stand well; but, if it touch iron along with the least watery moisture, it will be changed by it. As it is brighter than most yellows used in oil, and indeed than all at present in use, except the king’s yellow, it is much received into practice. It has been supposed to be a native earth, and is said to be found in the neighbourhood of Naples; but this is dubious, as the different parcels of it vary too much from each in specific qualities to allow the supposition of their being native earths of the same kind, at least with respect to such as are to be obtained from our shops; for I have met with some that was of a very different composition from the common. The uncertainty with regard to the genuineness renders this pigment less valuable, as it is less to be depended upon with respect to its holding its colour. Whether, however, it is an earth that is at present generally sophisticated, or what the preparation of it is, we are at present ignorant of, as it is brought from abroad; and this makes it more difficult to give marks of its genuineness; which may therefore be best gathered from its appearance and manner of mixing with the oil, in which the more adulterate kinds differ from the common.
Though Naples yellow is of a gritty texture, yet it is best to use it as it is obtained, and only grind it with the oil; for it does not well bear levigation with water. But if such levigation be nevertheless practised on it, the greatest care must be taken to employ an ivory spatula in the place of a pallet knife; which would certainly injure the colour, if it were touched with it while wet; and even when moistened with oil, the iron is in some degree injurious to it.
p. 93
Of yellow oker.
Yellow oker is a mineral earth, which is found in many places, but of different degrees of purity. When free from other earths and heterogeneous matter, it is a true yellow of moderate brightness: and, as its texture suits it for all kinds of painting, and that it will never fly in the least, it is a very valuable colour with respect to its utility, though of low price.
There is no other preparation of yellow oker necessary than levigation: and for nicer purposes washing over; to undergo which its texture is extremely suitable.
The goodness of yellow oker may be distinguished by the brightness and fulness of its yellow colour; and if it be bright, it cannot be too cool. But as it is not unusual to mix it with Dutch pink, and set an extraordinary price upon it as being extremely good, that imposition must be guarded against; which may be done by heating it to the degree that will turn paper brown; which if it be genuine will make little or no alteration in it; but if it be adulterated in this manner will give an apparent foulness to it.
. . .
p. 100
Terra de Siena unburnt.
Terra de Siena, as we have said before, speaking of it as a red when calcined, is a native ochrous earth, brought from Italy. In its uncalcined state it is a deepish warm yellow, and but slightly transparent either in oil or water. It is much less used uncalcined than calcined: but, nevertheless, as it is a deeper yellow by many degrees than any of the other okers, and of a superior brightness, it might be used with advantage, as it will stand equally with the best.
When terra de Siena is used uncalcined, it ought to be extremely well levigated and washed over otherwise it is apt to lie heavy in the oil; which is probably the chief reason why it is so seldom used in an uncalcined state; though as much wanted for some purposes as the calcined for others.
CLASS IV. Of green colours.
. . .
p. 110
Terra verte.
Terra verte is a native earth, which in all probability is coloured by copper. It is of a blue green colour, much of that teint which is called sea-green. What we have in common here, is not very bright, but being semitransparent in oil, and of a strong body in water, and standing equally well with the best pigments, it is very much adapted to answer some purposes in both kinds of painting; though it is not so generally used by those to whom it would be serviceable as it merits. Mr. D’Acosta says, in his book of Fossils, that there is a kind which is very bright, and is found in Hungary: if it could be procured here, it would certainly be a very valuable acquisition to oil painting; as the greens we are forced at present to compound from blue and yellow, are seldom secure from flying or changing.
Terra verte, as brought from abroad, is of a very coarse texture; and requires to be well levigated, and washed over: but no other preparation is necessary previously to its use. The only method of distinguishing its goodness is by the brightness and strength of its colour.
CLASS VI. Of purple colours.
p. 112
Of the true Indian red.
The true Indian red is a native ochrous earth, of a purple colour; and, before the cheapness of the fictitious kind, occasioned it to be rejected by the colourmen, and consequently disused by painters; was constantly brought from the East Indies, and sold in the shops. At present it is very rarely to be found; but when it can be met with, it is certainly very valuable (there being no other uncompounded purple colour in use with oil) as well for the force of its effect, as for the certainty of its standing: but the common kind, now fallaciously called by its name, has been, by degrees, from accommodating it to the purposes of house painters, made to vary from it till it is become intirely a different colour, being a broken orange instead of a purple.
The true Indian red, when it can be procured, needs no other preparation than grinding or washing over: and it may be easily distinguished from any fictitious kind, by its being more bright than any other oker which can be made so purple; and if it be rendered artificially purple by any addition, the fire will soon betray it; into which the genuine may be put without any hazard of change.
CLASS VII. Of brown colours.
pp. 118–119
Of brown oker.
Brown oker is a fossile earth, the same with the other okers, except with regard to purity, and the teint of its colour, which depends on calcination, either in the earth or artificially. It is of a warm brown or foul orange colour; and, as it can be absolutely depended upon for standing, it is valued by some in nicer kinds of painting, but most used, being of very low price, for coarser purposes.
When brown oker is used for more delicate kinds of painting, it ought to be well levigated after it comes out of the hands of the colourmen, if had of them in the gross state in which it is commonly sold: but whoever would have it in the most perfect condition, must wash it over: which treatment should indeed be bestowed on all pigments of an earthy texture.
p. 119
Of umbre.
Umbre is an ochrous earth of a brown colour. It was formerly used in most kinds of painting; but is at present neglected except by some in water colours. It is valuable on account of its property of standing well, which it has in common with most other native earths; and it is supposed to have a more drying quality than other okers, which has occasioned it to be much used in the making drying oils, the japanners gold-size, and the black oil lacquer.
The umbre is frequently burnt previous to its being used; which renders it more easy to be levigated; but it gives it at the same time a redder hue. Whether it be used in a burnt or unburnt state, it is necessary, however, to wash it over, when it is used in miniature painting, or for any nicer purposes; and that is all the preparation it requires.
. . .
CLASS VIII. Of white colours.
p. 127–129
Of troy white or Spanish white.
The troy white or Spanish white is chalk neutralized by the addition of water in which alum is dissolved, and afterwards washed over.
It is used by some in water colours as a white, and may be thus prepared.
“Take a pound of chalk; and soak it well in water. Then wash over all the fine part; and, having poured off the first water, add another quantity in which two ounces of alum is dissolved. Let them stand for a day or two, stirring the chalk once in six or eight hours; wash then the chalk again over, till it be rendered perfectly fine, and pour off as much of the water as can be separated from the chalk by that means, taking off the remainder of the dissolved alum, by several renewed quantities of fresh water. After the last is poured off, put the chalk into one of the cullender filters, with a linnen cloth over the paper; and, when the moisture has been sufficiently drained off from it, lay it out in lumps to dry on a proper board.”
p. 128
Of egg-shell white.
Egg-shell white is used by some in water colours; and preferred to flake or the troy white. It may be thus prepared.
“Take egg-shells; and peel off the inner skins. Then levigate the shell to proper fineness; and wash over the powder.”
CLASS IX. Of black colours.
p. 129
Of lamp black.
LAMP black is the soot of oil collected as it is formed by burning. It is a brownish black: but nevertheless, being of a good texture for mixing either with oil or water, and drying well with oil, it is the principal black at present used in all nicer kinds of painting: for notwithstanding ivory black far surpasses this in colour, the gross and adulterate preparation of all that is to be now obtained has occasioned it to be greatly rejected.
The lamp black is made by burning oil in a number of large lamps in a confined place, from whence no part of the fumes can escape; and where the soot formed by these fumes, being collected against the top and sides of the room, may be swept together and collected: and this being put into small barrels is sold for use without any other preparation.
The goodness of lamp black lies in the fullness of the colour and the being free from dust or other impurities. The lightness of the substance furnishes the means of discovering any adulteration if to a great degree: as the bodies with which lamp black is subject to be sophisticated are all heavier in a considerable proportion.
. . .
pp. 131–132
Of blue black.
Blue black is the coal of some kind of wood, or other vegetable matter, burnt in a close heat where the air can have no access. The best kind is said to be made of vine stalks and tendrils: but there are doubtless many other kinds of vegetable substances from which it may be equally well prepared. It is, when good, a fine bluish black colour useful in most kinds of paintings for many purposes; but is rarely to be had at present well prepared, and therefore much neglected in most nicer cases.
Those, who desire to have blue black perfectly good, may prepare it in the manner above directed for the ivory black, from the vine stalks or tendrils, or any other twigs of wood of an acid taste and tough texture, but the soaking in oil, prescribed for the ivory, must be here omitted.
The goodness of the blue black consists in the cleanness and blue cast of its black colour; and the perfectness of its levigation, which should be managed as directed for the ivory black.
. . .
pp. 162–165
CHAP. IV. Of the manner of compounding and
mixing the colours, with their proper
vehicles for each kind of painting.
SECT. I. Of the colours proper to be
used with oils, and the manner of
compounding and mixing them with the
oils and dryers.
THE colours proper to be used in oil, for red, are, vermilion, native cinnabar, lake, scarlet oker, common Indian red, terra de Siena burnt, (and mixt with white), red oker, Spanish brown, Venetian red and red lead : – for blue, ultramarine, Prussian blue, ultramarine ashes, verditer, indico, and smalt; – for yellow, King’s yellow, Naples yellow, yellow oker, Dutch pink, light pink, masticot, common orpiment, terra de Siena, unburnt and mixed with white, and turpeth mineral; – for green, terra verte, verdigrise, distilled verdigrise, or chrystals of verdigrise, and Prussian green; – for purple, true Indian red; – for brown, burnt terra de Siena (unmixed with white,) brown pink, brown oker, umbre, and asphaltum; – for white, white flake, and white lead; – for black, lamp black, ivory black, and blue black : these are all the colours which are at present in use for oil painting in this country; and when they are perfect in their kinds are fully sufficient to answer every purpose. The immediate preparation of them, and the manner of compounding them with the oils and dryers may be managed thus.
Okers of every kind, as also all the earthy and metallic bodies, in which are included ultramarine and its ashes, ought to be well levigated by a good stone and muller, with water; and washed over, before they be mixed with the oils, when they are intended for more delicate purposes : and lake, brown pink and Prussian blue, which being of a gummy or glutinous nature, would again acquire a cohesion if levigated in water, may be ground to an impalpable powder by adding spirit of wine to them instead of the water, in which state they will then continue when they again become dry; and be much more easily and thoroughly commixed with the oils. Lamp black demands no preparation; nor does the asphaltum require to be commixed with oil; but with spirit of turpentine to thin it, if it be of too thick a consistence to work with the pencil.
In levigating lake or any of the pinks, as also King’s yellow, Naples yellow, or verdigrise, with water or spirit of wine, great care must be taken not to use a knife or other iron implement; which would greatly injure the colours. Instead of such knife, a thin piece of horn may be employed to take the colours off from the stone, or to scrape them together as they are grinding : and caution should likewise be used with regard to the boards on which they are dried; and the place where they are reposited during the drying : for the sun or dust will be very apt to deprave some of them in this state, if they be not well kept out.
The pigments being thus duly prepared may be ground with the oils, either on a stone or muller, when they are wanted in greater quantities; or are intended to be kept; or by the pallet-knife, on the pallet, where they are immediately to be used : but they should be perfectly mixed; or the oil will be apt to separate, and the colours fail of their due brightness and effect. For convenience the colours designed for the nicer kinds of painting, after they are ground with the oil, are put into pieces of bladders; and tied into a kind of ball; in which state such as be perfect will continue good a long time; and the bladder being prickt and squeezed, the colour is forced out by small quantities, as is required for use.
For coarser work, the colours demanded in great quantity are ground by hand or horsemills with the oil; and the others on a stone with a muller. After which, they are put in pots; and mixed there with oil of turpentine and drying oil, according to the particular purposes to which they are employed.
Vermilion, Lake, Prussian blue, brown pink, King’s yellow, and sometimes vermilion, are apt to be backward in drying; and require, therefore, to be mixed with oil that is old and well disposed to dry; and where brightness is requisite, the nut or poppy oil should be used with oil of turpentine: but where the brightness is of less moment, old linseed oil with a third of drying oil, and the same proportion of oil of turpentine, may be substituted. But the proportion of these, and all dryers, must be adequated to the occasion, as discretion may dictate, according to the quicker or slower disposition of the pigments used; and the time that may be conveniently allowed for them to dry. Flake white should be also used with nut or poppy oil only; and to these oils many add white vitriol and sugar of lead, as well as the oil of turpentine, when they are to be used with this or other pigments that are too slow in drying; but the effect of those substances, when used in this manner, is very dubious, as I have observed before.
pp. 174–175
SECTION III.
Of the colours fit to be used in fresco;
or, painting with size; and
the manner of mixing or compounding
them with the proper vehicles.
BY fresco painting was originally meant all paintings on walls, or other parts of buildings exposed to the open air; but at present it signifies in common language the grosser paintings in water, where size is used. The same colours which are employed in miniature painting, may be used in this kind with size: only this method being principally confined to scenes and grosser sorts of work, where the effect depends more on the perspective art and the opposition of the colours, than on their brightness, the dearer kinds are wholly omitted, or sparingly used.
The best method of compounding the colours with the vehicles, is to mix the size in water; then to levigate the colours in part of it; and afterwards to put each kind in a proper pot; adding as much more of the melted size as will bring it to a due consistence for working; and mixing the whole well together in the pot with a proper brush, or wooden spatula. If the quantity of water originally put to the size, do not render it sufficiently fluid for grinding the colours, the fault may be easily remedied by adding warm water to it; and the same may be done likewise, if, after the mixture of colours, the whole be found too stiff for working.
The compositions of the colours and size must be prevented from drying, by tying bladders over the pots, or some other such means; for when once they are grown dry, they cannot be brought again to a working state without difficulty and trouble.
Though the grounds and the laying in, and grosser parts of this kind of painting, be done by this mixture of the colours with size; yet in higher finished works, that require the finer colours, the more delicate parts may be best executed by using the gum-waters or ising-glass, as above directed in miniature painting: by which means the mixing up greater quantities of the dear colours may be avoided, though otherwise necessary; as it is impracticable to keep minute quantities from drying; which, in the size, renders them unfit for working, till they are again reduced to proper condition by means of heat; but, in the others, is not attended with the least inconvenience.
pp. 201–204
CHAP. VI.
Of the grounds for the several kinds
of painting.
SECT. I. Of the grounds for oil painting.
THE substance or matter on which oil paintings are made, unless in very particular cases, are canvas, wood, or copper-plate. The preparation or covering of these, in order to their receiving the proper colouring, must be therefore different according to the different substance in question.
The pieces of canvas prepared by proper primings, are then by painters called cloths. But these cloths, though they are dispensed with in general, because painters think it too much trouble to prime them themselves, and therefore make shift with what the colourmen will afford them, who on their side likewise consult nothing but the cheapest and easiest methods of dispatching their work, are yet at present prepared in a faulty manner in several respects. In the first place, the whole covering is apt to peel and crack off from the cloth, by the improper texture of the under coat, which is formed of size and whiting; and is both too brittle, and too little adhesive, either to the cloth or upper coat, to answer well the purpose. In the second place, the oil used in the composition of any paint used on such grounds, is extremely apt to be absorbed or suckt in by them; and consequently to leave the colours, with which it was mixt, destitute in a great degree of what is necessary for their proper temperament. This is called, though improperly, the sinking in of the colours, and is attended with several inconveniencies; particularly, that the effect of the painting appears very imperfectly while the colours are in this state, and deprives the painter, as well as others, of the power of judging properly of the truth of the performance. It is indeed practised sometimes to varnish over the ground, which will prevent the sinking in; but there is a hazard in this, that the upper coat may leave the ground; and the painting consequently come off. Whoever therefore would have good cloths, free entirely from this disadvantage, must direct the preparation of them themselves; and they may produce them in perfection by the following means.
“Let the cloths be first well soaked with drying oil laid on hot, and when nearly dry, let two or three coats of drying oil and red oker, mixed as thick as can be worked, be spread over it. Then, the last being dry, let the cloth be brushed over with hot drying oil, as long as it appears to sink in: and, lastly, let it be covered with a coat of white lead and oil, rendered grey, or of any other colour desired, by admixture of the proper pigments. This last coat may be polished to a due degree by rubbing with a pumice stone, or by glazing it with the glass polishers used for linnen, and called callender stones.”
In priming wood, or preparing it to receive the oil colours, the same errors are generally committed: for the method almost universally practised is to clear-coat it, (as it is called) with size and whiting; and then to cover it with white lead and oil: but the ill effects of such a method are still greater, in this case, than in that of canvas; as if any moisture find access to the wood, the paint rises in blisters, which are liable to be burst, and to cause a flaking off and peeling of the paint, in a very detrimental manner. For paintings of any value the wood should, therefore, be brushed over with hot drying oil, as long as it will soak it in; and then covered with a coat of white lead, or flake, coloured according to what may be desired. Even in the case of house or coach painting, the clear-coating with size and whiting, ought to be omitted; and, in its place, a coat of drying oil with some white lead and oker, but not so much as to make it stiff, should be used as the first priming, instead of the size and whiting; which method would both preserve the wood much better, and prevent both the blistering and peeling; and in some degree the sinking in of the colours that attend the common method.
When copper-plates are used, there is no occasion for any other priming than one coat of oil, and lead, or oker, rendered of the colour desired: but such plates are seldom employed but for delicate and elaborate paintings. The surface of the priming ought to be made as smooth as the plate itself, by rubbing with the pumice stone, or glazing with the callender stone. But there is another method very effectual for making a fine ground on the copper-plates; which is the using flake white and fat oil, with any colour required; which being laid on the plates placed in an horizontal position to dry, will polish itself very highly, by the running of the oil. The oil used for this purpose should be thoroughly fat: which, though not at present to be had of colourmen, may be easily made by the method below taught, with very little expence trouble; and this method of producing grounds by fat oil, perfectly smooth, secured from any sinking in of the colours, and in all other respects much better than any other, may be practised with advantage on cloths or wood, as well as copper-plates; the cloths being first prepared for the last coat in the manner before directed; and the wood soaked with drying oil.
p. 207
SECTION III.
Of the grounds for fresco painting.
THE substance or matter on which fresco are generally made, is either plaster or canvas [sic!].
When plaster of Paris without lime is used, and the surface made smooth, there need no further preparation: but when any lime is used in the plaster, and any other colours are employed, except earths, or such as are prepared from mineral substances, the surface should be washed over several times with size and plaster of Paris free from lime, and suffered to dry then thoroughly before it be painted upon.
When canvas is used, as for scenes, &c. it must be coated with strong size and whiting till it be of a thickness to take a water polish, and then it should be primed with plaster of Paris free from lime, and mixed up with size as before directed for the plaster; as it will then bear lake, carmine, or other colours prepared from vegetables without preying upon, or changing them. The manner of giving the water polish is by rubbing over the ground with a wet cloth till it be perfectly smooth.