The gilding on wood, called oil gold, cannot be burnished, and is always of the natural colour of unwrought gold. It has the advantage that it may be washed and cleaned with water, which burnished gold never can. It is often used for picture frames, parts of furniture, and mouldings of apartments; as it stands the weather, it is also employed for outdoor work. The surface to be gilded should first of all be rubbed smooth, if stone with pumice, if wood with butch rushes, if a very bright level effect is desired. After this it should have its priming of glue size, and two coats of oil paint and one of flatting. To enrich the colour of the gold, these last may be laid down in red or yellow. White, however, is usually preferred, as the darker colour renders any imperfection in the gold-sizing more difficult to detect. When the last coat of paint is thoroughly dry, rub it over with wash leather, to render it smooth and free from dust or grit. If there are any patterns or figures which are to be left ungilded, they should be lightly pounced over with white to prevent the gold leaf adhering to them. Another way is to paint them over with the white of egg diluted with water. If any gold sticks to this, it can be easily washed or wiped off with a moistened handkerchief.
When all is ready for sizing, strain sufficient size through muslin, and put some out on the palette, adding to it enough ochre or vermilion, mixed with oil alone, to colour. Then with a stiff hog-hair tool commence painting it on the surface, taking care to lay it on smoothly, and not too thick. If put on too thickly it runs, and leaves wrinkles in the gilding. Size always from left to right, beginning at the top of the surface, and working downwards. Move the brush lightly and firmly, mapping out the surface to be 3ized into several squares, and finishing and cross hatching each before proceeding onwards. If there are patterns to be left ungilded, carefully trace round their outline first with a sable pencil, and then fill in the interstices. When the whole surface is covered with size, give it a thorough inspection to make sure there is no faulty portion, and if there is, delicately touch in the size with a small pencil. When very perfect gilding is required, it should be sized twice, the first coat being allowed to dry thoroughly before the second is applied. In carved work, be careful to dip the brush down into the hollows of the carving. It is a good plan to size over night, so as to gild in the morning.
But all size does not dry alike, sometimes taking 12 to 24 or 30 hours before it is ready for the gold leaf; in damp weather or positions, always more than in dry. The readiness of the size can only be ascertained by the touch. If on being touched by the finger the surface, daubs or comes off, it is not ready, and must be left; if it feels clammy and sticky, it is sufficiently matured. If too dry it must be sized again. The books of gold leaf should always be placed before a fire 1/2 hour previous to use, in order to thoroughly dry the gold and make it more manageable. When all is ready, shake out several leaves upon the gold cushion, and blow them towards the parchment screen. Then carefully raise one leaf with the blade of the knife, and place it on the cushion, gently breathing on it to flatten it out. If it cockles up, work it about with the knife-blade until it lies flat. • Then replace the knife in its loop under the cushion, and taking the tip, pass it lightly over your hair, thus acquiring sufficient greasiness to enable the gold to stick to it. Lay the hairy portion of the tip upon the gold leaf, and then raising it, apply it to the sized surface.
As in sizing, work from left to right, and be specially careful to let each leaf overlap slightly, so as to avoid gaps and spaces. Lay on whole leaves as far as the space allows, and then proceed to gild the curves and corners which need smaller pieces. Place a leaf flat and smooth on the cushion, and then taking the knife in the right hand, draw the edge easily and evenly along it with a gentle pressure. Divide the leaf into as many pieces as required, and lay on as before. When the ground is complete, give a very careful inspection to make sure there are no portions ungilt, however small, and mend them at once. Next take a piece of cotton wool, and gently dab or press the gold down all over, finally brushing off the superfluous pieces either with cotton-wool or the camel-hair brush. It is a good plan to stipple the gold with a large stiff hog-hair tool, quite dry and clean, as this gradually softens and removes the marks of joining and other little imperfections. Finally smooth the gold with a clean piece of wash-leather, and it is completed.
With regard to gilding with japan-ners' size, the same instructions apply, except as to the time necessary to wait between sizing and gilding. If japan-ners' size is used pure, it will be ready in 20-30 minutes, but better gilding can be made by mixing one-third oil size with two-thirds japanners' size. This will be ready in about 2-4 hours from the time of putting on. When all the gilding is finished, dilute one-third very clean and pare parchment size in two-thirds water, and brush it all oyer the surface of the gold to enrich and preserve it. If it is necessary to gild in a position much exposed to touch, as the base of a pillar, or string-courses, it is as well to give the gold a coat of mastic varnish thinned with turpentine. There are various processes which tend to enrich and vary the effect of gilding. Glazings of transparent colour are sometimes applied for the purpose of deadening its lustre. Raw sienna passed thinly over a sheet of gold gives it a leathery appearance. A good effect may be produced by stencilling a small diaper in umber, sienna, or Indian red, over gold, especially if there is foliage or arabesque work upon the gilding, as the small diaper affords an agreeable relief.
This is the easiest mode of gilding; any other metallic leaves may be applied in a similar manner.