Below is an excerpt from “The Craftsman’s Handbook” – D. V. Thompson’s English translation of “Il Libro dell’Arte,” an intriguing guide to methods of painting written in the 15th century Florence. Page 68.
“A size which is good for tempering blues and other colors. Chapter CXI.
And there is a size which is made from the scrapings of goat or sheep parchment. Boil them with clear (or light-colored) water until it is reduced to a third. Know that it is a very clear size, which looks like crystal. It is good for tempering dark blues. And apply a coat of this size in any place were you have happened to lay in colors which were not tempered sufficiently, and it will re-temper the colors, and reinforce them, so that you may varnish them at will, if they are on panel; and blues on a wall the same way. And it would be good for tempering gessos too; but it is lean in character, and it ought to be rather fat for any gesso which has to take gilding.”
What I find interesting with this is addressing the idea of colors dusting, or not being stable enough for a top coat to varnish. In other words, the unstable colors would smear onto the rest of a composition. This is similar to my process during scenery restoration. The dusting pigment needs to be “re-tempered.” Cennini writes, “apply a coat of this size in any place were you have happened to lay in colors which were not tempered sufficiently.” I spray a solution of size to stabilize the colors on the backdrop. The glue attaches loose pigment back to the surface of the fabric. It is crucial that you get the perfect strength, however, or it can make the surface shine and brittle.
Here is an example of pigment dusting…I apologize about the photo quality.
And to end with the following chapter in “The Craftsman’s Handbook” that made me grin….titled: “To make a glue out of lime and cheese. Chapter CXII”
“There is a glue used by workers in wood; this is made of cheese. After putting it to soak in water, work it over with a little quicklime using a ittle board with both hands. Put it between the boards; it joins them and fastens them together well. And let this suffice you for the making of various kinds of glue.”
