Water Gilding Picture Frames and Wood Carvings

THE TECHNICAL SIDE: WATER GILDING PICTURE FRAMES AND WOOD CARVINGS^*

Antony Denning, SHA

The Heraldic Craftsman No. 12, Spring 1993

A finished frame or carving must first have any knots painted over with shellac, then the whole piece is sized with a thin coat of warm rabbitskin glue, which seals the surface and raises the grain of the wood to provide a ‘key’ for the gesso. All Joints and knots are then covered with silk or linen stuck down with rabbitskin glue.

This stage is followed by the application of successive layers of gesso, usually somewhere between four and forty, but if it is to be carved, it can be built up to as much as a centimetre thick. Gesso is made by mixing warm rabbitskin glue with whiting. The proportions of whiting to glue and the strength of the glue cannot really be given as a recipe because they vary, but they are nevertheless important. In Northern Europe the usual filler is Calcium Carbonate whilst in Southern Europe it is usually Calcium Sulphate. Kaolin can also be used. The gesso is applied warm with a flat long bristled hog brush, each successive layer being applied before the previous one is completely dry, but not before all the wet shine has disappeared.

The gesso provides a smooth surface to take the gold and a ‘cushion’ which allows the gold to be burnished. It also gives an opportunity for the surface to be textured. Plain gold can flatten the form. Texture helps to give a visual balance. Textures and patterns can be worked in the gesso by building up shapes, carving, cross hatching, fluting, hassling and sanding. The surface is smoothed with fine finishing papers, or where these are impractical, with a slightly damp rag.

Before the gesso has dried completely it is painted with thin layers of coloured clays called ‘bole’. First, yellow bole, which is a yellow ochre, is painted as a wash over the whole surface. The vehicle is again rabbitskin glue, slightly thinner than for gesso. Two or three coats are usually enough to give an opaque yellow; brushmarks must be avoided. Yellow bole will not usually take a burnish so the parts which are to be burnished are then painted with red bole which burnishes well (originally this was Armenian bole which is now rare and expensive) and, perhaps, after the red, the highlights may be given a coat of black bole (this was very popular in the 19^th century). The next day the bole is polished with a stiff, very short, bristled brush to remove any roughnesses and to give the surface a sheen.

The loose-leaf gold is cut into convenient sized pieces, but as large as possible, on a gilder’s cushion. Draughts and breathing have to be avoided because gold leaf will float effortlessly into the air at the slightest puff. When the leaf is on the cushion it can be breathed on to make the wrinkles flatten. The gilder’s tip, which is a broad thin brush, is used to transfer the gold from the cushion to the piece, it first has to be charged with static electricity by brushing the hair on one’s arm or the nape of the neck, before it will pick up the leaf. (If you meet a man with gold highlights in his hair, don’t make any snap judgments, he may be a gilder.) The gold is applied to the bole by wetting the surface with gin or size, water and alcohol. The leaf is attracted to the wet surface and nearly always leaves the tip without difficulty. When gilding into a hollow, the theory is that one gilds from each side with enough gold projecting over the edge to find its own way down to the bottom. (Not all gold leaf seems to know what is expected of it.)

When the gold is virtually dry the parts to be burnished are breathed on and burnished with an agate burnisher. Other areas may be worked on with punches to give pattern, i.e. if these areas were not patterned or textured before gilding. There may be areas which have to be toned with colour or matting agents etc. These, after treatments, are to make the whole piece easier to see and to improve its appearance. If the piece is being restored, or one wants it to look old, it can be “distressed”, which is applying artificial wear to exposed areas, as would have happened naturally, given time. Another decorative treatment which is sometimes used is to paint over the gold with egg tempera, then to draw a design through to reveal the gold. This is called Sgraffito and is sometimes seen on polychromed sculpture.

• Glues: Rabbitskin Glue: though originally derived from rabbit skins, the term is now applied to a fine glue made from the hide, bone etc., from various animals. It is soaked overnight then heated in a double saucepan.
• Parchment Size: is more trouble to make because you have to boil the offcuts of parchment yourself, but it is said to be better for making good gesso.
• Gelatine; can also be used and is very fine.
• Boles: bole comes in other colours apart from the yellow, red and black mentioned above. They are not much used, but blue and white may be mixed with other colours, perhaps to make a mauve to go under silver leaf. Different colours have been in fashion at different times in history. Local colour variations were often due to locally available clays. Gouache is sometimes used in place of bole.

Gold Leaf has changed little since the Ancient Egyptians and hardly at all in the last two hundred years, though machines have replaced man to a certain extent. Hand beating is still considered essential for the final beating of from two to five hours with a ten-pound hammer. One ounce of gold produces enough leaf to cover more than 180ft². Standard gold is usually 22-23% carat, but there are other tones which are alloys of gold with copper or silver and various other metals. These are likely to tarnish eventually. A very satisfactory leaf for heraldic helms is called Caplain or Black Gold, which is an alloy of gold, silver and palladium.