For the use and good and profit of anyone who wants to enter this profession."
Cennino Cennini, sometime before 1437
TO PREPARE THE PANEL ( either or oil or egg tempera)
PART 1: SIZING
Coating or soaking a material -- wood, paper, or cloth --with a gluelike substance which acts as an absorption barrier is called "sizing". The glue is called "size". A panel of masonite or similar particle board (Older books warn about "tempered" masonite, but there is no such thing any more.) or a well cured and dried hardwood panel, not too large.
â€¢ Dry granulated rabbitskin glue
â€¢ Distilled water (tap water will probably do, but it's better not to risk mineral contamination causing problems down the line)
â€¢ A double boiler
â€¢ Measuring cups and spoons
â€¢ Sandpaper, medium grit
â€¢ A dust mask
â€¢ A large, inexpensive priming brush
1. Mix the rabbitskin glue: Sprinkle 1 1/2 tablespoons of dry glue granules into one cup of water (This makes an amount suitable for a large panel or several small ones. I regret my appalling American ignorance of the metric system which leaves me at a loss to convert these measurements). Stir briefly, then allow to soak overnight. (In a pinch you can simply proceed, but a soak of at least a few hours makes a better glue.)
2. Sand the smooth side (or both, if they are both smooth) of the masonite until it is no longer shiny.
3. The next day, warm up the glue mix in the double boiler until it is quite hot. Do not allow it to boil. Stir it smooth; this should not take long.
4. Using the priming brush, brush the warm glue onto the panel, wetting it thoroughly but not leaving puddles. I do one side of the panel and the edges, then let it dry overnight and do the other side.
NOTES: The glue, if you have any left over, will cool to a rubbery gelatin. Just warm it up again when you need to use it.
But don't make more than you will use in a few days. It will go bad. Very bad.
You could do more than one coat of glue, but usually one should suffice.