Cyclopedia of Painting/Gilding

by George D. Armstrong

GILDING.

Gilding may be broadly understood to mean the application of metals in thin leaf form to decorative purposes, by the use of mordants and vehicles. Originally limited in scope to the application of gold loaf, it has now become a general practice to substitute many kinds of metal, both in imitation of gold, and in order to produce other metallic color effects. This is not altogether to be regretted, as the use of the more precious metal in such a form that it is ultimately totally lost to the community is a deplorable waste, which is not entirely defensible, especially as it draws a large quantity of the metal away from its more legitimate use in the arts of the goldsmith and metal worker. The small proportion used for really high-class decorative work, as in illuminating and permanent decorative schemes and pictures, is in proportion less than one per cent of the enormous amount used for commercial advertising, and the overlaying of plaster and composition picture frames.

The various metals in common use for gilding in the leaf form are:

Platinum.

Gold, in many degrees of fineness and tint.

Alloys of gold and copper.

Alloys of gold and silver.

Alloys of copper and silver.

Alloys of copper and tin.

Silver.

Aluminium.

The alloys are known as metal d'or, Dutch metal, gold metal, etc. The commonest and cheapest forms are thick and brittle in quality, while the better degrees of gold leaf are beaten to extreme thinness, the malleability and ductility of the metal allowing as many as 2,500 leaves, 3 inches by 3+¹⁄₄ inches, to be obtained from 1 ounce of fine gold, or to put it in another way, the total thickness of 300,000 leaves is less than 1 inch. Gold leaf is usually put up in books of 25 leaves, each leaf being 3+¹⁄₄ inches square. It is sold by the 1,000 leaves—viz., 40 books. Silver leaf is usually 4 inches by 4 inches, and metals are made in both sizes, and larger.

Gold leaf is termed white, pale, medium, deep, extra deep, citron, red, etc., according to its color. Gold is readily damaged in the book by handling, damp, and shaking, for this reason good gold leaf of recent make should be selected. The best work cannot be produced by any other. It should be kept in a dry place, and may, with advantage, be placed upon a hot plate, or in the oven prior to using. The red powder on gold books is put on to prevent the gold sticking to the leaves of the book, it is bole, a red earth from Armenia, of peculiarly flaky, smooth, and soft texture. A red French clay is sometimes used for the same purpose.

Methods of Gilding. The various methods of applying gold leaf used by painters and decorators are termed: Oil gilding, Japan gilding, and Water gilding.

These methods vary in detail upon different kinds of grounds. Oil or Japan gilding is used upon painted surfaces, or grounds that have been strongly sized or varnished.

Oil Gold Size. Oil gold size is a preparation of fat linseed-oil, which has, by exposure to the atmosphere, lost its power of absorbing oxygen, and become viscid and less hard drying, it may be prepared by exposing linseed oil to the air and light in a wide, open-mouthed vessel for about six months. To make it usable and give it a little body and color, ochre is ground up in about one-third of the whole quantity and added to the whole bulk, a little driers, usually litharge, is also required, and, if too thick for use, it must be thinned to proper consistency with boiled oil. A small quantity of good varnish, one part to twenty, added to gold size, gives it hardness and additional luster. Good oil size will be ready to receive the gold at any time between twenty-four hours and a week from the moment of using it, and the longer it holds its tackiness the better is the result, provided that the size ultimately dries firm and hard, like a piece of gold-beater's skin.

Japanners' Gold Size is a quick varnish drying in about half-an-hour to two hours, and is ready for gilding as soon as sufficiently dry. It must be gilded upon at once when this is the ease, as the tack soon changes into a hard varnish surface.

Gilding can be done with varnish, but the excessive gloss gives a blackish look to the gold, and as the varnish hardens it loses its hold of the metal, which will then wash off with soap and water. Notwithstanding this fact, it is often used in large proportions added to gold size by certain decorators, who admire the additional gloss, but do not trouble about durability.

Many special sizes of a varnish nature are made for sign writers.

Water Gold Sizes vary in their nature for different purposes. For gilding on prepared wood, papier mache, plaster, or composition, as for picture frames, two kinds are used, burnish and matt gold size.

Burnish Gold Size is made from pipeclay and black lead, with a small quantity of mutton suet added in the grinding. It can be purchased ready made, and is used with ordinary parchment or gelatine size as a binding medium. Gilding on this size will take a good polish, or burnish with an agate burnisher.

Matt Gold Size. Matt size is for gold which is required to have a matt or dead surface, and is made from pipeclay, Armenian bole, and other materials. It can be purchased ready for mixing with the clear parchment or jelly size.

Isinglass Gold Size. Gilding upon glass is done with isinglass size. Take a pinch of best Russian isinglass, put it into a pint of water, and stand the whole in a covered jar in the oven for a few hours, when dissolved or cooked add a ¹⁄₄ pint of spirits of wine and strain or filter through white filter paper. The spirits of wine removes the solid or waste portion of the isinglass, and also serves to counteract grease on the glass, or in the hairs of the brushes used, its action is similar to that of wine in milk.

Clear Size for Gold. Gold is often clear sized to improve its color and prevent blooming. This size, as well as that used for matt and burnish work, is best prepared from finest gelatine, or from boiled parchment cuttings.

Tools for Laying Gold. The operation of gilding is the same, whatever process is used, in as far as laying the gold is concerned. The best and general method is by means of a cushion and tip. The cushion is a small board about 8 by 5 inches, covered with flannel, and over this a tightly stretched chamois leather. A draught screen of parchment is fitted round one half of it, this to prevent the wind removing, the gold from the cushion. It has a thumb strap beneath, and loops for the knife, etc., and is held like a palette on the left hand. The other tools required for the laying are a gilder's knife and a tip.

The knife is a long flexible blade of equal breadth throughout its length. The tip is a flat brush made by setting a row of hairs, either camel or badger's, between two pieces of card. The fingers of the left hand hold the tip and knife alternately when either is not being used by the right hand. Dabbers and camel-hair brushes, and mops, are required to press the gold down in its place, and remove superfluous scraps.

Laying Gold Leaf. The size being ready to receive the gold, about a dozen leaves are put in a heap in the back part of the cushion, then the cushion is taken in the left hand and the knife in the right.

The gold is taken from the book by merely opening each leaf and gently blowing the gold out on the cushion. With the knife a leaf of gold is taken to the front of the cushion, laid squarely, and deftly blown out flat, cut to any size required by a sharp jerking, saw-like movement of the knife not like ordinary cutting, the knife is then transferred to the left hand, and the tip to the right, the gold is then taken up by the tip and laid upon the work. The whole process is extremely simple after practice. Breathing must be carried on gently through the nostrils, so as not to disarrange the gold. When blowing a leaf flat, aim a smart jet of air right into the center of the leaf, sudden and short. When cutting, lay the edge of the knife, which must not be keen, on the gold leaf firmly, give a little jerk, lift it up, and the gold will separate. Take care not to cut the leather of the cushion. The knife must not be sharp enough to do so. If the gold does not at once adhere to the tip, pass the same lightly over the hair or beard to slightly grease it; this also sets up a magnetic action which assists to hold the gold. It must not adhere too firmly to the tip, or the gold will tear in transferring itself to the gold size. Always allow each leaf to lay ¹⁄₈ inch in laying, to secure a good joint. Use whole leaves wherever possible, and fault up every hole and crevice before dabbing down. Well press down all joints or there will be a slight gap apparent at the junction.

In gilding a plain surface, hammer well down with a firm touch and a good cotton wool pad before skewing off, and then skew with a soft new stencil tool, using a circular motion, and polish with a soft piece of cotton wool. Laying gold upon ordinary oil or Japan gold size is sometimes done by a process of transferring. This process is economical and useful for outside work, or for etched and partial gilt work. To accomplish the process, the gold must be what is known as transfer gold, gold leaf which has been put upon tissue paper. Sheets of thin tissue paper are cut into convenient sizes and slightly waxed with a tablet of white wax. When pressed against the gold leaf in the book, the leaf adheres to these waxed sheets and is from them in turn transferred to the work. The waxed sheets being slightly adhesive, only those portions of the leaf that are in contact with the gold size leave the tissue sheet, and so there is no waste. The tissue being somewhat transparent the operator can see exactly what gold is still left upon the tissue, and utilize every portion of it for the work in hand, he can also see when the gold size has not been covered with the gold. Gold can be transferred to the tissue leaves without the necessity of waxing them, by merely interleaving the gold book with tissue and putting the book into a copying-press and well pressing.

The exceptions to these two methods of laying the gold are fanciful and individual, the most general being what is termed laying from the book. When gilding a large flat surface, the gold leaf can be laid direct from the book and much time saved thereby, by the use of a long-haired tip which can take up a leaf at a time without the necessity of cutting. The odd spaces and small bits are afterwards filled from the cushion in the usual manner. Another method is to dispense with the tip, and by taking the book in the left hand, and opening it with the right to turn the leaves straight on to the work. This is a great saving of time for large letters out of doors or for large flat surfaces of oil size gilding, but it requires some dexterity to be sure and economical.

All gilding for interior decoration, and all out-door gilding that can be conveniently left long enough before gilding, should be done in oil gold size. The exceptions are, when lime is an object of importance, or where the work is fine and intricate, as in small lettering.

To Prevent Gold Sticking to Ground. The ground for gold sizing must be free from any tackiness, hard, dry, and impervious. If it is not so it must be coated with some preparation to prevent the gold sticking where it is not required. The white of an egg beaten up with a little water is the best preparation upon varnished or enamelled work. The white of one egg to 4 ounces of water is sufficiently strong. Upon ordinary painted work, a good rubbing with a pounce bag, that is, a small calico bag filled with fine sifted whiting, will suffice. A little size and water is also effective, and if a little whiting is added to it, it is still more so. White of egg must not be used too strong, never more than two-thirds water to one-third egg. This is the least detrimental to the luster of the gold. Ordinary painted work that has to be partly gilt and then varnished, may be prepared by rubbing with a piece of very fine glass paper and some dry whiting. Whiting preparations have a tendency to cause the gold size to run.

The gold size must be laid evenly and sparely. If laid too heavily it will crinkle up after the gilding has been done. It is sometimes necessary to add color to the gold size in decorative work, so as to see better where the size is put on level, etc. Tube colors may be used for this purpose, and they should always approximate to the color of gold as nearly as possible, as the gold leaf is full of innumerable small holes, and the color used in the size has an effect upon the appearance of the gold when laid. Chrome, burnt sienna, vermilion, or ochre are suitable colors.

Gold size should never be gilded unless quite ready. The size should be just tacky enough to hold the gold leaf, but never wet enough to smear or move if rubbed with the finger tip. Gold laid upon too wet size will turn black and lusterless. The precise condition is ascertained by the application of the clean finger tip, and practice will enable the operator to judge very accurately.

Turpentine should not be used as a thinner in gold size, because it leaves behind it, after evaporation, a resinous oil, which never properly hardens. A little boiled oil is the best thinner. Japanners' gold size may be thinned with a little turpentine if both are heated to boiling point together.

Oil gilding should always be well washed down with clean water and a soft sponge, and then sized with clean gelatine size, this washing hardens the oil, and the size protects and preserves the gold and gives it a more uniform luster, in place of the broken metallic brilliance it has as the result of its beating. Before washing, it should be carefully pressed down with cotton wool, all faults made good, and the whole dusted off with cotton wool or a camel-hair dabber.

In gilding enriched and molded surfaces, the gold will sometimes require double laying, in order to reach the interstices of the work.

All waste gold, known as skew, should be saved and used for dusting into the carved portions, and when these are dusted out, the skew should be carefully collected in a tin canister for future use, or for disposal to the dealer in old gold and silver.

Burnish and Matt Gilding. Burnish and matt gilding are much alike in method of procedure. They are principally used for enriched ornament, cornices, and picture frames. The work is brought up to a good surface in size and whiting, and then coated with five or six coats of the matt size or burnish size, as the case requires, each coat being rubbed down with very fine glass paper, and the size laid on with a camel-hair brush and allowed to dry thoroughly between each coat. When the ground has a sufficient number of coats to be perfectly solid, the gold is laid with water only. The size is well wetted with water in a camel-hair brush, and the gold laid on the water, which, as it dries, carries the gold on to the size coat and fixes it there. The leaf must be laid immediately following the water while it is yet live, to accomplish this quickly, the expert gilder uses the water brush with his right hand by clenching it with the two little fingers in his fist at the same time as he has the gold upon the tip held between the forefinger and thumb of the same hand. The flowing water catches the gold from the tip, and spreads it out smoothly on the surface of the water in the moment or two between the application and the absorption of the water by the distemper ground. This completes the gilding as far as the matt portion is concerned, except for a final clear sizing and sometimes coloring or coating with ormolu.

The burnished portion, however, requires polishing or burnishing. This is done at the moment the gilding is dry, and before it becomes so hard as to be brittle. An agate or flint stone, set in a handle, is the burnisher. These are of different shapes. They are rubbed lightly against the gold, which takes a remarkably high polish, and retains it. Burnished gold must not be sized.

Burnish and matt gilding are confined to the flat or curved plain portions of the work, and are done first. The enriched and fancy parts are afterwards oil-sized and gilded in the usual manner.

Ormolu for matt gold is prepared from best garnet shellac and white sticklac dissolved in spirits of wine, and tinted to the required depth with dragon's blood, a few drops are added to the usual gelatine or parchment size to produce an even, lusterless and rich surface of any desired depth.

Glass Gilding. Gilding upon glass is done in the same manner as described for water gilding, isinglass size being used in the place of water. The glass is well cleaned, freed from grease, and set before the operator at a slight angle, sometimes the glass is upright, as in a window, and has to be done in that position. The isinglass size, before described, is used in precisely the same way as the water in water gilding, and the gold laid on the flowing size so as to stretch itself out as the size recedes. The size must be used freely and allowed to run off quickly. It must not be strong, the weaker it is the brighter will the finish of the gold be. The less size there is remaining between the glass and the gold and between the two coats of gold, the better polish can be obtained.

In all other methods of gilding the gold is attached from the back of the leaf, and the finished work shows the unalloyed brightness of the metal, but in the case of glass gilding, the size comes between the gold and the eye, and the glass interposes a further medium, so that it is at once apparent that the cleaner the glass, and the clearer and thinner the film of size, the less is the brilliance of the gilding interfered with. The purity and cleanliness of the size and glass will be assured if the size can be laid upon the glass without cissing or gathering. If it runs off like water on a duck's back, the glass is greasy or the size is not clean, or perhaps the water used is too hard, boiled rain water makes the best size, but it must be clean and clear.

Gilding on glass requires a second coat in order to make a solid job. The first coat of gold when dry is lightly polished with finest cotton wool, and fixed and burnished by scalding with very hot water as near boiling as can be used without splitting the glass. It may be poured over from the spout of a kettle, so as to run over the whole of the gilding, and then down on to the ground, or laid over with a broad 4-inch camel-hair flat. This removes the scum of the size from between the gilding and the glass and adds to its clarity and brilliance. The work may then be carefully polished with a piece of finest cotton wool. It is then allowed to dry and the whole of the gilding and clearing with hot water repeated. After this the gold is backed up by a coat of hard Japan or varnish which will dry in about eight hours and have a perfect gloss. In cold weather the whole of the glass must be treated with the hot water whether gilded or not, or breakage will result from the inequality of expansion produced, and if the day be frosty, the job must be done very cautiously in a hot shop, or defended. The water must never be boiling.

The gold used for glass gilding is specially prepared, being more even in thickness than the ordinary gold, and put up in books of special paper that does not require dusting with French chalk or Armenian bole to prevent the gold adhering to the book. The gold thus supplied is much cleaner than that used for general purposes. It is important that glass gilding be made to dry off quickly and that no time be allowed to elapse between the operations, or it will accumulate dust and get discolored.

Although gilding on glass is looked upon as a difficult matter to successfully carry through, all the difficulties are overcome by the exercise of cleanliness. The cleanliness of the glass may be tested by breathing on it, and if the moisture evaporates quickly, leaving the glass clear, it will do. Glass may be made chemically clean by the use of dilute nitric acid, and well rinsing with water.

Tissue paper is a good glass polisher. Filtered rainwater makes the best isinglass size, or distilled water, as it is free from metallic taint.

Gilding upon paper, parchment, and vellum can be best done by using a size made from yolk of eggs and glycerine. This is ground together with a little ochre and thinned with water. If used in a very liquid state as a mere water wash size, and the gold is laid directly thereon, as in glass gilding, it may be tooled or burnished. All gold work should be sized before writing or painting upon it.

Platinum and Silver Laying and Metaling. Platinum leaf is used in the same manner as gold lead, and is applicable to all the same purposes.

Silver leaf and gold leaf of very pale tint, that is, which contains a large proportion of silver, should never be laid on the oil gold size, neither should metals which are subject to oxidization, as the oil has a strong affinity for oxygen, and the oxidization of the metals is set up and goes on more rapidly. If used upon a spirit size or water size, and well protected with lacquer or spirit varnish, these metals will be perfectly lasting. Their durability depends entirely on their perfect enclosure and envelopment in an air-tight case of lacquer or varnish, both under and above them.

Japanners' gold size, with, or without, the addition of a little Venice turpentine makes as good a size as can be had for metals. There are many special sizes for the purpose prepared ready for use, but nothing is better than a good full bodied japanners' size exposed to the air for a few days to fatten a little.

Aluminium leaf may be used best on a mixture of ochre ground in oil and japanners'. It is reported to be unchangeable, and is so as far as it has been tested in actual decorating. It cannot be lacquered into a good gold, but silver leaf can. Silver is more lustrous than aluminium, which has a rather leaden look when used alone. It makes a pretty combination with gold, being grayer than silver. The cheaper metals can be laid by hand, as they are so thick as to stand handling freely, and can be cut into pieces with a pair of scissors.

The principal qualification for success in gilding is a deft and delicate handling of the metals, especially gold leaf, and there must also be a ready recognition of the possibilities and peculiarities of each kind. Always remember that whatever the condition of the under size or ground, it is hermetically sealed up when the leaf is put on, which thus prevents any change or further drying in the ordinary way, so that if gold is laid on soft coats of paint, they will not all harden off together, but will go on working under the gold, expanding and contracting, and will ultimately ruin the gold leaf.

Bronzes. Bronzes have the same qualities as the baser leaf metals, and the same precautions must be observed in using them. They must not be mixed with oil varnishes, or oil mediums, but can be put upon japanners' gold size, or upon any spirit varnishes in powder form. They can be mixed and applied as liquids in any spirit varnish, or in size or gum, though the tendency of gum to become acid times turns the bronze black. In bronzing with the powder, the size, usually japanners' gold size, is applied, and when tacky, the bronze is dusted on with a rabbit's foot, a wad of close cloth, or a chamois leather pad. The bronze is protected by a thin coat of lacquer, and then varnished in the ordinary way.

Bronzing should never be varnished over with oil copal varnishes, as it will rapidly lose color and oxidize if so varnished, some of the commoner house-painters' oak varnishes have so little oil in them that this effect does not follow rapidly. If metals, silver, or gold be sized with a clear jelly of gelatine size, or thinly lacquered, they may be varnished with any kind of varnish, as the interleaf of size will stop the direct action of the varnish upon the metal.

Bronzing is sometimes used over paint to give the effect of metal. Thus a piece of iron casting may be painted green or copper color, and then the highest portions of the relief touched with bronze. This is done by coating the article with japanners' varnish or gold size, and when tacky dusting over a little powder bronze, which can be applied by a piece of cloth or velvet rubbed in the powder. The bronze should not be applied to the bare oil paint. The color of the bronze must bear a correct relation to the color of the paint used.

Lacquer for Metals. Various lacquers are used to give gold or metal a different color. Any lacquer can be made from an ounce of good shellac dissolved in half a pint of spirits of wine, and tinted with saffron, turmeric, sanders, or other dye-woods, dragon's blood, or any of the aniline powders. The most useful colorings are turmeric and dragon's blood, a colorless lacquer may be used, and the tinting done by the use of transparent oil colors in varnish.

The house painter often has to re-lacquer small brass fittings. These are better gilded and then coated with French polish or a good lacquer. This does not apply to handles, but to certain hooks, curtain pole ends and brackets, bell pulls, etc., clean, and give them a coat of patent knotting before gold sizing, gold size with japanners', and gild in the usual way.

Preparing Open Grain Wood and Stone for Gilding. To prepare rough cut deal, ash, open grain oak, or stone, for gilding, give a couple of coats of French polish and spirit varnish in equal parts, or two coats of patent knotting, then gold size in the usual manner. Japan gold size sometimes works cloggy in fine lettering. When working indoors at line gold lettering on a black ground, if the Japan size be stood in a jar of hot water it keeps fluid and works extremely well, setting quickly when once on the work. It must not be too hot. A pot may be filled with hot water and the size in a smaller pot stood in it.