|From Planting Along The Verge|
from The Craftsman’s Handbook by Cennino d”Andrea Cennini
“You must know what bone is good. Take bone from the second joints and wings of fowls, or of a capon; and the older they are the better. Just as you find them under the dining-table, put them into the fire; and when you see that they have turned whiter than ashes, draw them out, and grind them well on the porphyry; and use it as I say above. “
he goes on with these mixing instructions
“take less than half a bean of this bone, or even less. And stir this bone up with saliva. Spread it all over the little panel with your fingers; and, before it gets dry, hold the little panel in your left hand, and tap over the panel with the finger tip of your right hand until you see that it is quite dry. And it will get coated with bone as evenly in one place as in another.”
or you could go buy some gesso but the idea of the spit and bone is strangely appealing to me at the moment.