Gelatin is dissolved in warm water to make a transparent size for certain gilding uses, notably in glass gilding and gilding the reverse side of mirrors. Available in leaf or capsule.
The amount of capsules you need to mix with warm water to create size varies accoriding to the application and the leaf used. The thicker and heavier the leaf, the more gelatin is needed to make a strong enough size. The following are guidlelines that have been advised to us by our skilled gilding clients.
For glass gilding:
Gold leaf - 2 capsules per pint of hot water
Heavier metals, such as silver leaf - 3-4 capsules per pint of hot water
Imitation leaf - May require as many as 6 capsules per pint of hot water
Some clients add alcohol (for example, a double measure of gin although isopropyl alchohol can be used) once the size has cooled. The gelatin is for adhesion and the alcohol is added as it thins the mixture and helps it flow more easily.