Gilding on wood

mirror


Since ancient times, gold is use to covered objects of art, worship, or precious, to enhance them. This metal, the only one to have the particularity of not oxidize, was an immortal and divine symbol.

Thus we find statuettes of wood, metal objects, stone, partially or completely covered, usually with a very thin gold leaf, so as not to clog the support details.

For wood, there are two main techniques of gilding: the water gilding and the gilding mixing.

The gilding, the oldest, is still practiced, especially for low-relief supports supporting a lot of other processes, such as wood (frames mirrors or paintings), wrought iron, commemorative plaques, but also roofs (Les Invalides), sculptures and other decorations (Opera) in Paris.

Because gold is a very ductile metal, it is possible by hammering to obtain very thin sheets (a few microns) without breaking the metal wire. Gold leaf is laid flat on a support then caught with a broad brush called "palette" on which she clings because of static electricity. Gold leaf is then deposited on the surface to brown, sometimes prepared with egg white to ensure adhesion. A polishing ensures the final appearance. In the gilding French polishing is carried out using an agate stone in the shape of a wolf's tooth that was used in the eighteenth century for this operation.

 

gold leaf


A- The technique of gilding on wood:

The preparation of primers:

First, prepare wood to receive gold.

Indeed, wood is one of the organic materials that react most to the hygroscopic variations: it increases volume when the surrounding air becomes wet or shrinks in the presence of dry air.

It also has the distinction of having a more or less pronounced veining as gasoline. Gold foil laid over bare wood, would highlight the grain, which significantly interferes with the understanding of volumes and would be counterproductive: mimic solid gold.

The elders have therefore developed an intermediate coating that is applied between wood and gold leaf, mask the appearance of the surface, and follows changes due to moisture. This buffer coating consists of an inorganic filler (finely ground chalk), a binder (rabbit skin glue) and a solvent (water). Since the sixteenth century, rabbit skin glue has replaced sheepskin glue.

This coating, called "primer" since the Middle Ages, is applied to 60 ° C over 10 to 12 thick layers. The surface is then smoothed, sanded (with horsetail or fine sandpaper) and then covered with two very light coats of "plate", also called "Armenian bole": it is a kaolin clay, consisting of earth and iron oxide, blood orange coloration that facilitates burnishing gold.

Once the installation of the dish is complete, the gilder polishes the surface so that plateful small grains will line the remaining gold leaf. Traditionally, this operation was carried out using a dogfish skin (which is now protected), hence the name of this step the "chiennage".

Then comes the application of gold leaf, which is very delicate. Indeed, given their fragility, they can not be touched by hand and are placed in bulk on a cushion. To move the gilder uses the flat of a knife to brown to position them one after the other on the front of the cushion, and then he blows it to flatten, the "jonflage".

 Once dry medium, the gilder then proceeds to browning. This step consists of crushing the gold with an agate stone to make it shiny. It provides a contrast to the matt remained parties. Burnishing can only take place on a water gilding.

 If gold adheres poorly and detaches the gilder fills every empty space with small pieces of leaves, the "mending".

 Then the "matting" comes protect and conserve gold; applying glue to very diluted rabbit skin.

 The patina is finishing.

 

agate dorure

 

B- Two methods of gilding on wood:

 

1) The water gilding

The water gilding or tempera is traditionally used on wood process.

We can apply gold leaf, silver, copper, palladium, etc.

Gold leaves are applied to the water on the plate, the adhesive in contact with the liquid, is regenerated. They may then be covered with a slight skin adhesive layer (highly diluted in water): the caulking. Glue through the porous sheets and clings to the coating. Gold is taken "sandwich" becomes dull and more resistant to erosion. The brightnesses are obtained by crushing the agate stone.

The gilder sometimes leverages the thickness of the primer to execute engravings or set stones.

This gilding is the only one that was used for all gilded wooden objects until the end of the eighteenth century. The elimination of corporate rules had the effect of authorizing mixed gilding on the same subject: the mixing for flat parts, water for bright parties.

 

2) gilding mixing

The process for mixing (siccativée linseed oil, ...) is easier and faster than the previous gilding. This inexpensive technique does not offer the same quality of matt and gloss contrasts the water gilding; the oil film slightly impasted volumes.

A new mixing has emerged since the 1970s: the mixing water (vinyl resin emulsion in water). It is even easier to work, but provides a thicker film than mixing with oil, which makes the metal surface is less clear.