Recipes for successful formulas can be found in historic documents illustrating the combinations of ingredients which could be used to produce a paint. Natural resin varnish was added to oil-based paint to provide a hard, more glossy surface. A translucent layer applied to protect the paint and to impart a more uniform gloss surface. Usually made from linseed oil with natural resin varnish added. Usually used on interior plaster surfaces.
Various recipes call for a large variety of additives to increase durability.
Casein paints were also used for exterior surfaces.