Viewing Topic "Gilding Gesso"
Alabaster is a fine-grained massive type of gypsum or calcium sulfate hydrate. It does not have a specific chemical formula because it is a natural mineral of indefinite composition.
Terra Alba is a natural gypsum with the approximate chemical composition of calcium sulfate dihydrate.
Italian Gesso is a natural gypsum with the approximate chemical composition of calcium sulfate dihydrate.
Although these minerals have the same approximate chemical composition, the powder forms of these products vary in particle morphology, crystallinity and particle size. They are mixtures of hydrates of calcium sulfate (i.e., hemi-hydrate, dihydrate, etc.). They are also derived from different locations in Italy and have different uses in painting, gilding and other arts and crafts.
I'm looking to make my own gilding gesso (slaked plaster of Paris, Lead carbonate, sugar, and seccotine).
On here, there are 3 types of base that can be used, but only 1 has the checmical composition and the 2 others have descriptions that say "Recommended in Cennino Cennini's treatise on painting..."
What is the difference between these 3:
1. Alabaster (510-11ALB)
2. Terra Alba (Product code: 510-11TRA)
3. Italian Gesso (Product code: 510-11GL)
As I can tell, they are all Calcium Sulfate, Terra Alba is the only one that says that it's Dihydrate.