Читать книгу Practical Graining and Marbling - Paul N. Hasluck - Страница 4

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The art of graining consists in working transparent colour over an oil ground, the ground being of a colour that will match the lightest tone in the markings on the wood. The transparent colours used for the general markings match the colours in the real wood, and are applied with large brushes; the effect is further assisted by still darker touches of colour, put on here and there in places with smaller brushes. To produce a good piece of graining, the most important matters to be considered are—the ground on which the graining is to be worked, the figuring, the overgraining, the glazing, the tools, the state of the colour and the manner of applying it, and, because there are several modes of procedure, the particular process to be adopted. There are three different kinds of graining—namely, water colour (distemper), spirit colour, and oil colour—outdoor work is done in oil, water colour is used for facility and for fine gradation, and spirit colour for quickness. The several methods are frequently combined, as, for instance, water colour over oil, in order that the second coat of the figure may not disturb the first. If water colour is used over water colour, the under coat must be fixed with a mixture of equal parts of varnish and turpentine.

It is assumed that the reader already is acquainted with the practical elementary stages of brush work, as the plain painting is termed, and that he is capable of producing a good ground upon which the graining can be worked. The ground of the graining is very important, for although a skilful man could work on a while or even a poorly constituted ground, yet he could do far superior work on a ground of good tone and in good condition. The ground is a technical term involving two distinct ideas: namely, surface and colour. A properly prepared surface should be free from grittiness, from coarse brush marks, from dents, etc., and should be hard and smooth. The amount of gloss depends on the proportions of linseed oil and turpentine in the grounding paint, and is a matter for individual preference; some grainers prefer a groundwork of a brilliant bright tone, trusting to the brown glazing colour to break it down; others prefer to have the ground of a dull colour, and work a brighter tone of graining colour over it. Some prefer the colour mixed up with three parts oil to one of turps; others prefer the colour to be made up of half turps and half oil. The former gives a hard gloss suitable for oil-graining with steel combs. For water or distemper graining, more turpentine, giving a dull gloss, is better; for this class of work two coats of varnish are ultimately required, while, if the ground is hard and oily, only one coat of varnish is necessary, as the varnish binds the pigment when the water has evaporated. A good ground cannot be obtained by the use of dead or flatting paint; there must always be sufficient oil in the colour to allow it to be thoroughly spread and laid off, and so ensure the absence of coarse brush marks. The colour of the ground is determined by the wood about to be imitated. Correct judgment as to the combined effect of ground and graining colours is the result of much careful observation and experience.

The preparation of the woodwork has been already mentioned. Rough and imperfectly got-up woodwork is often grained in imitation of oak, the graining being supposed to hide the defects; but to obtain a serviceable grained surface, a smooth ground is essential. Ordinary woodwork as it comes in its rough state from the joiner can be filled up or levelled in the following manner: First, well rub it down with No. 1½ glass-paper, and then remove the dust with a painter’s dusting brush. Coat any knots with the transparent spirit varnish known as patent knotting (see p. 126), when this is dry, prime the wood with a paint made by mixing together three parts of white-lead, one part of red-lead, and one-tenth part of paste or liquid driers, then dilute with three parts of linseed oil and one part or less of turpentine. When this priming is dry, putty up any nail holes, etc., and allow the work to stand untouched for a day or two. The next coat should contain much less turpentine and no red lead, and should be stained a few shades darker than the desired ground, this being obtained by the application of a third coat. Strain the paints before using, and lightly glass-paper down between each coat.

Oil paint is apt, after a time, to present a greasy surface, so that it will ciss, even if oil colour is laid over it—that is to say, the colour will not lie, but will curl up into small beads. This tendency, as well as the want of affinity between water and oil, makes it necessary to prepare the ground for the reception of the graining colour. This may be done in several ways. A small quantity of dry whiting may be rubbed over the work with a piece of flannel, and the superfluous whiting brushed away; or the work may be brushed over with weak ale to which a small quantity of whiting has been added, or with water mixed with fuller’s earth; or stale beer alone, or even size, may be used, the liquid being allowed to dry before the graining is begun, but care should always be taken not to use too great a quantity or too strong a solution. Anything of a solid nature, such a whiting, should be cleared away when it has accomplished its purpose. The ground should be slightly glossy, and should not be glass-papered, especially for light woods, as the marks of the papering are liable to show.

Properly prepared graining colour works freely and cleanly not only from the brush but during the subsequent manipulation; it also combines the correct and particular colour with the transparency of the pigment which, when laid upon the ground, is to imitate the colour of the genuine polished wood. This matter of combined colour effect must be thoroughly grasped, as it is the chief working principle upon which the imitation of wood is based. An opaque body graining paint which shall give the appearance of oak, without necessitating the two distinct grounding and graining processes, is impossible. As soon a white-lead is mixed with the pigments from which the graining colour is made, the transparency and richness of the latter are decreased; whilst the graining colour alone, being only a stain, lacks the preservative qualities of a white-lead or body preparation.

The graining colours should be purchased in bulk, and if to be used merely for practice, obtain such cheap grainers and stainers as burnt umber, burnt sienna, vandyke brown, Venetian reds, Italian ochre. These may be obtained at 6d. per lb., and after a little experience the madder lakes, scarlets, Prussian blues, etc., may be procured. Graining colours should be of the best, and in every case be ground very fine, since they are always used as transparent colours.

Mathieson’s oak scumbling is supposed to be a good substitute for graining colour. It has the appearance of a pigment ground into a stiff paste with prepared linseed oil. In use, it merely requires thinning with linseed oil and turpentine in proportions to suit the time allowed for drying. It may be made to dry in one hour if diluted with liquid driers instead of oil, but unduly forcing the drying properties of paint is not advised. It should be borne in mind that the oxidising action set up by a drying agent is greatly in excess of that of the atmosphere, and does not cease with the drying of the surface, but continues and brings about a consuming and destroying process. Mathieson’s scumbling is made in three degrees of colour—light, deep, and dark. The inventor considers those to be sufficient, used either separately or compounded, to produce all the shades required for the many varieties of oak graining.

The following remarks apply to grounds and colours for oak graining. The basis of all oil ground colours for oak graining should be white-lead ground in linseed oil. Any coloured pigments that may be added to obtain a dark ground can be considered only as stains, as none of them furnishes the opacity, solidity, or durability, for all of which qualities white-lead is so noted. Of course, if a very dark ground—such as that for “antique” oak—is required, not so much white-lead is used in its composition as for light or medium grounds. It may not be out of place to say that the grainer who relies on the use of white-lead to obtain a good ground seldom produces those unnaturally bright and garish grounds that always offend the trained eye. As a general rule, in making grounding paint, sufficient white-lead for the purpose, together with one-tenth the quantity of patent driers, should be broken up in linseed oil, and the staining pigments added and well mixed in. The paint should be strained through a mesh, and then thinned to a working consistency with about two parts of linseed oil to one part turpentine. This gives a good gloss, but if a ground is required which may be quickly grained, the proportions of the linseed oil and turpentine should be reversed.

The following are recipes for ordinary oak grounds: (1) For light oak, use a mixture of white-lead and yellow ochre (sometimes with a touch of chrome to brighten it); Oxford ochre and Venetian red are used for dark oak, with the addition of burnt umber; and raw sienna for still darker wood. A rich tone of buff, given by vermilion and chrome, is sometimes adopted. (2) A buff ground is made with 7 lb. white-lead, ½ lb. of yellow ochre ground in oil, ½ lb. of driers, mixed with linseed oil 2 parts and turpentine 1 part, and strained when thin enough for use. (3) White-lead, stained with orange chrome, and thinned with one raw oil to two turps. (4) Mix 1 lb. of white-lead, 2 oz. of patent driers, and 2 oz. of Oxford ochre. Thin with oil and turps.

As regards the graining colour, for water colour work, it should be ground up very fine in beer, and kept in a bottle tightly corked; when used, it should be thinned with weak beer and water. A permanent water colour graining is obtained by melting gum arabic in hot water, and mixing enough of the gum with the graining colour to bind it. If the gum is in excess, it will cause cracks. Softness, flatness, variety, and permanence are produced by this method. The grain of oak is frequently done in spirit colour. Gliders’ whiting is ground up stiffly in turpentine, and stained to the required tint with burnt umber and raw sienna, which are also ground up stiffly in turpentine. A small quantity of japanners’ gold size and boiled linseed oil or ordinary varnish is now added to bind it, and it is then thinned with turpentine and strained through a piece of muslin into a large-mouthed pot, when it is ready for use. If too much varnish is used, the colour will set so quickly as to be unmanageable. Only a small portion of graining, just enough to allow for combing, can be done at a time, as the colour dries so quickly. The lights are taken out with a fitch, dipped in a fairly strong solution of soda in water or in turpentine. Both the soda and the turpentine should be stained with a little burnt sienna, otherwise the markings will be too staring. Hold in the left hand a rag on which to wipe the fitch, so as to prevent the fluid running down and spoiling the work. Spirit graining should not be varnished for twenty-four hours, and even then must not be rubbed too much.

When oil is the medium in oak colour, raw sienna, with burnt umber or vandyke brown, according to the depth of colour required, is finely ground in linseed oil. Patent driers is then added, this acting as a megilp, giving substance or body to the colour; ½ oz. of patent driers to 1 lb. of colour, mixed with equal parts of oil and turpentine, is the proportion. Without this megilp the colour will be flat and uninteresting. To get the ribbed appearance of the grain of oak, beeswax, soft soap, lime-water, and rain-water are often used when patent driers is not available. The method of preparation is as follows: Wax must be thoroughly incorporated with oil by shredding the wax into an earthenware receptacle, covering it with linseed oil, and stirring with a red-hot poker till the wax is thoroughly dissolved; then add the staining colour, well mix, and dilute it with turpentine. An excess of wax with the colour will cause the combing to stand up too much. In the natural wood the markings are depressions, but in the graining they appear as ridges of colour. The markings should not, therefore, stand up more than is absolutely necessary to produce the desired effect. The lines must to a certain extent be distinct, although softened down in places. Soft soap must be broken up with either patent driers or whiting, and thinned with boiled oil; or it may be made up into a lather with plain water, and in this state mixed with oil colour. The objection to soft soap is its alkaline nature, all alkalies weakening and destroying paint. Lime must be slaked in water (about 2 lb. of lime to 1 gal. of water), allowed to settle, and the clear liquid poured off for use. Sufficient lime-water is mixed with the graining colour, and well beaten up. But graining by this method is liable to fade, the lime destroying the colour, and causing the paint to crack. Rain-water used alone, and beaten up thoroughly with the colour, has many advantages; it does not exert injurious action, the colour does not spread, and as soon as the colour has set, the water evaporates.

The best megilp (seldom, however, used for graining on account of the expense) is made from mastic varnish and boiled oil. To make it, pour the boiled oil into the varnish, and use the jelly formed by the mixture. As a hard and fast rule cannot be laid down for mixing graining colours, the proportions depending on the conditions under which the work is done, the colours should always be tested before use. The colour should rub out cleanly, easily spread, and the lines left by the comb should keep their place, not running into each other or settling down. A method of oak graining now seldom practised consisted in first laying the markings in with a flat, square-edged fitch, dipped in a mixture of sweet oil and beeswax. When this was dry, the graining colours (made up with weak beer) were applied. When the work had thoroughly dried, the beeswax was carefully washed off with turpentine. Ordinary graining colour is best made with about equal parts of oil and turpentine, to which is added paste driers (one-eighth of the whole bulk) with sufficient colouring matter.

The colouring pigments used as ingredients of all oak grounding and graining paints may be briefly classified as either opaque or transparent. Of the former class are the chromes, Oxford and yellow ochres, and Venetian red, which should be used only in making stains for grounding paints. Raw and burnt sienna—or Terra di Sienna—raw and burnt Turkey umber, and vandyke brown, may be considered as being transparent, though that quality is possessed by them in a varying degree. They are sufficiently translucent to give due effect to any coloured ground upon which they may be superimposed. For purposes of glazing and overgraining, ivory and blue-blacks and Prussian and indigo blue may be used, though the two latter are required seldom.

Prussian blue is a good working and staining colour, and a quick drier. Venetian red is cheap but permanent, and must be procured ready ground in oil. It is useful for grounds.

Lemon and orange chromes, when of best quality, are chromates of lead. They are brilliant, have good body and covering power, and make good tints when mixed with white. When used in oil they must be protected by varnishing, especially if exposed to impure air, which in time will turn them black. The chromes destroy Prussian and some other blues. The yellow chromes are made in three shades, known as Nos. 1, 2, and 3; the No. 4 shade is the orange chrome, a deep rich colour. The shades are varied by increasing the chromate for deep orange, and lessening it for the pale yellows. These colours are injured by damp and impure air, sulphur fumes, and hydrogen; but the orange chrome is said to last better than orange oxide of lead.

Chrome, of either middle or orange tint, may be useful to a slight extent in staining ground colours, when very bright and rich imitations are required. Generally, however, chrome conduces neither to good colouring nor to the attainment of a natural woody effect. The chrome-yellow tint sometimes forms a ground for light oak, whilst orange-red is used for medium oak.

White-lead, the basis of all graining grounds, is one of the most frequently used pigments, and also one of the most faulty. It is made by suspending rolls of ordinary thin sheet lead over malt vinegar or pyroligneous acid, in close vessels, the evaporation from the acid being kept up by a steam bath underneath. The lead is thus reduced to a white powder ready for being ground with linseed oil into a paste. White-lead improves by keeping, and for good work should be stocked for at least twelve months after purchase. Very pale and old linseed oil should be used in the thinning, otherwise it will probably soon discolour. It is, however, about the best pigment for preserving wood, etc., from the effects of the weather. Tests for white-lead are described on p. 125. Zinc white is an oxide of zinc, but it does not possess so much covering power as white-lead. It, however, does not discolour, and is a very pure pigment. It is a substitute for white-lead, but is not so employed in the practice of graining.

Vermilion is used only in the most exceptional cases; it can be had as a fine dry powder, free from grit, and is a very brilliant colour in oil. The best quality only is permanent, and that is a sulphuret of mercury. Chinese red, or vermilion, is of a deep crimson tone, but has bad covering power, and, unless well protected, will soon fade under the action of light and impure air.

Indigo possesses great body, and is a good glazing colour. It is not very durable, and is injured by impure air.

Ivory black is made by placing ivory dust in a covered crucible exposed to a great heat. An inferior colour known as bone black is made by treating bones in a similar way. Ivory black, the deepest and purest of the blacks, being somewhat hard, requires very careful grinding, and unless ground very fine is useless. It is best ground in turpentine, and diluted for use with turpentine, gold size, and a little varnish. In drying it will become dull, so that it should not be used unless it is afterwards to be varnished. If thinned down too much with turpentine it will not bind, so that when the varnish is applied it will rub off on to the rest of the work and spoil the whole. Ivory black, when purchased unground, resembles “drops,” and is sometimes called “drop black,” but bone black is prepared in the same way.

The various ochres—Oxford, yellow, Italian, etc.—are used only in the composition of grounding paint, and never in graining colour. Really, commercial yellow ochre is the only one of this class of pigment there is need to use, since the addition of a little Venetian red will give any warmer tint desired. This latter tint—a kind of burnt ochre—can alone be commended for obtaining warmth in grounds. Yellow ochre is not a very bright colour; it is best purchased in tubes, otherwise it is not thoroughly ground. Ochre is an earth found in most countries, and is of all shades, from the warm yellow of the Oxford ochre to the pale straw yellow of the French earth. The ochres are not liable to change through any chemical action, and may therefore be considered permanent.

Umbers, natural pigments consisting of a mixture of clays and brown hematite, are valuable on account of their transparency and of their good drying qualities when in oil; the latter qualities are so pronounced that umbers may be employed as drying agents. Raw umber is unsurpassed as a graining colour for light imitations, whilst burnt umber may be used for “antique” oaks from light to the darkest. In mixing grounds, also, umbers are invaluable. Raw umber does not injure colours with which it is mixed. Burnt umber is very permanent, and is sometimes used instead of vandyke brown.

Raw sienna is the yellow pigment used for very rich and light oak, but, properly, should seldom be required, as decided yellow and bright tones are not characteristics of real oak. The siennas are used in oak colours to produce a forced richness. Similar in nature and preparation to the umbers, they are more transparent, but lack the natural drying qualities of umber when used in oil. Siennas are used to produce those imitations which are obtained by the use of pigments ground in water; they are useful for graining in mahogany, maple, walnut, etc. Raw sienna is rather an impure yellow, but has more body than the ochres and is also more transparent. By burning it becomes burnt sienna, which has similar properties. Burnt sienna is a rich, transparent, and red brown pigment; gold size may be used as a drier with it. It dries better than raw sienna, and is very permanent, as it is not liable to change by the action of light and oxygen, or by damp and impure air.

Vandyke brown, a transparent earth pigment, is a very slow drier, and, if used in oil, requires to be diluted with little else than terebine or similar drying agent. It has a dark colour, inclining to neither yellow nor red, but yet extremely rich and deep. In oak graining, it is generally ground in water, its colour being warmer and richer than when used in oil. It is the principal pigment used in overgraining oak. It is a bog earth.

Neutral black and blues, previously mentioned, are also to some extent transparent. Blue-black in conjunction with vandyke brown is largely used for overgraining oak. Black enters into the composition of the dark, “drabby” grounds for “antique” oak. The effects of transparent blues may be regarded by some grainers as questionable; but it must be remembered that richness of colour in woods is only a matter of comparison and contrast, and, therefore, if instead of forcing the colour values by bright grounds, bright graining colour, and rich overgraining, some contrasting cool tones are introduced, it is possible to obtain more natural colour variety and yet retain the subdued contrasts of the real oak. Prussian and indigo blues are vastly different when ground in water from what they are in oil; whilst the tints are considerably mellowed by the final coating of copal or oak varnish. The first stages of oak graining should be worked in subdued tones rather than in false bright ones, and any desirable enrichment should be left for the glazing and overgraining to accomplish in preference to struggling in the final phase to modify early faults.

Megilp, which is mentioned on p. 34, is added to oil graining colour to ensure that the latter shall not spread when combed. In ordinary and cheap oak graining an excess of the drying agent is made to serve the purpose, but the megilp generally acknowledged to give the most satisfaction is a preparation of beeswax. A few ounces of pure wax is shredded and dissolved, by the application of heat, in linseed oil; add to the dissolved beeswax 1 pint each of linseed oil and oil of turpentine, 1 gill of terebine, and the pigments ground in oil. The wax must be thoroughly mixed with the other constituents, or the drying qualities of the colour will be affected (or the method given on p. 31 can be followed). It must be remembered that wax is not added as a drying agent, but solely to make the colour more amenable to the dividing and wiping out action of the combs.

The following are recipes for oak graining colours: (1) Light oak: 6 oz. of linseed oil, 2 oz. of turps, 2 oz. of burnt umber, and 1 oz. of patent driers. Mix well together and strain through muslin.

(2) Two oz. burnt timber and ½ oz. japan gold size, thinned with equal parts of boiled oil and turps; adding oil and turps lightens it.

(3) Four oz. of burnt timber, 1 oz. of patent driers, 2/3 by weight of raw linseed oil, and 2/3 of turpentine. For a warm colour add 2 oz. of burnt sienna; for a cold colour or new wood add 2 oz. of raw sienna.

(4) Half lb. of raw umber in oil, ¼ lb. of Oxford ochre in oil, ¼ lb. of putty well rubbed up on palette, ¼ lb. of driers. Well mix with equal parts of linseed oil and turpentine. Strain well.

(5) Dark oak and knotted oak: Mix ½ lb. of burnt umber with ½ gill gold size, or ½ gill terebine. Thin it with 3 parts of boiled oil and 1 part turpentine. Strain well.

(6) Two oz. of vandyke brown or 2 oz. of burnt umber; for a warm shade add 1 oz. of burnt sienna; for a cold shade, 1 oz. of raw sienna. Thin with equal parts of oil and turps, and add 1 oz. driers to ever pint of colour.

Distemper graining pigments are bound by the use of beer. Vandyke brown, however, does not require a binder for overgraining in water, nor do the sienna very often. When using black or the cool tones—either alone or in combination with warmer colours—a little beer is necessary, because black has no binding power; if mixed with vandyke brown in equal proportions, no binder will be required, but it is always best to ensure that the overgraining will not work up when the varnish is applied. In finishing “antique” oak in black alone, the wash must be strong in beer; for mixed washes, one-half beer is a safe proportion.

For a very light oak, the ground colour is made from white-lead paint, and is tinted to a decided cream with yellow ochre. The graining colour may be stained with raw sienna and raw umber, or the latter alone; the work may be overgrained in water with vandyke brown and weak blue-black, or indigo.

Ordinary light oak requires a clean buff ground, stained by ochre, and occasionally a touch of Venetian red or umber. Raw umber is suitable for the graining colour, though burnt umber gives a richer cast. For the overgraining, vandyke brown and blue-black are used.

Medium oak looks best on a warm buff, the red and ochre therein being slightly toned down with umber. Burnt umber alone makes a good graining colour, whilst vandyke brown is generally sufficient for shading.

The grounds for dark oak are best made with three pigments—ochre, burnt sienna, and burnt umber. In this mixture red should show prominently, but it should, together with the yellowness, be sobered by the umber. For the graining colour, burnt umber or burnt sienna and black may be used, overgraining with washes of black and vandyke brown, used either separately or together.

Very dark or “antique” oak has a neutral “drabby” ground, in which the red and yellow are subservient to the umber or black tones. The graining colour may be vandyke brown or ivory black and burnt umber in oil; blue black or ivory black is used for the overgraining. An overgraining of vandyke alone is rich, but transparent black tones are more characteristic of real antique colour. A little vandyke toning here and there is an improvement.