Gilding is an art that requires talent, savoir-faire, and skill, qualities that artisans obtain after years of experience. There are two basic techniques in applying gold or metal leaf to surfaces: oil and water gilding. Both techniques employ glue to adhere the leaf to the substrate, but the difference lies in the type of glue. This technique uses a water-based glue or size.
Gilding involves two specific stages:
Preparing the support
Laying the gold leaf
When using a gilding bole, you must prepare the surface before applying the gold leaf. Wood is generally used because it has a stable shape: sizing and several layers of white chalk mixed with hide glue are applied to the support.
There are two different stages to preparing hide glue:
Hide glue is usually available in a block, sheet, or grain form (rabbit, bovine, and porcine skin). You need to soak the hide glue first. Add water until it reaches the level of the glue. Leave to soak for 24 hours until it is entirely soft.
Remove from the water, drain and dissolve in a bain-marie without boiling, stirring continuously. When the glue has dissolved, remove it from the heat.
1 part of glue for seven parts of water
When dissolved, add the hide glue to white chalk. Reheat the mixture in a bain-marie when it cools. Apply the mixture to the surface. Between each layer, you may need to sand the surface until smooth. This primer is the base onto which you brush the gilding bole. The bole is a paste in yellow, red, and black colors. Mix this bole with twice its volume in warm hide glue. You’ll need two layers of bole.
Once the bole is dry, wipe the surface with a cloth to remove dust. Use a squirrel hair brush to moisten all the surfaces on which the bole was applied: if water drips are slightly colored, bole adherence is correct. Apply the gold leaves to the moist bole and leave to dry. Burnish the surface with agate.
Burnishing involves rubbing with agate stone in the shape of the surface by pressing relatively hard to inlay the gold sheet into the bole. Different shaped agates suit different contours and motifs for reliefs and sculptures.
The gilding is complete. Objects will retain their sheen for many years.