Glues and Sizes
This is a recipe for sizing a panel or gluing a fabric to a panel; if you want to size a canvas you'll need to dilute the solution or you can reduce the hide glue powder to 35-45 gr and still use 1 lit of distilled water. Prepare the same way as it is described down.
If the glue comes in sheets, they must be first broken into small pieces; a cloth wrapped around it will prevent its flying about.
Place the dry glue in a wide-mouthed glass container and pour the water fig.1; if the glue comes in sheets let to soak over night, it will be found to have absorbed water and to have swollen about three times its dry volume fig.2. If the glue is as a powder it will take only couple of hours. It is recommended to cover the glass with a clear-plastic wrap, to keep away the dust.
Then heat the glue in double boiler until the glue dissolves. Don't reach temperatures of glue higher than 70ºC. Always stir the solution; you can do it with the thermometer or with wooden rod; but be aware that it's clean and you never used it for preparing food. Cooking salt destroys the adhesive power of glue.
Glue must never boil otherwise it will loose its strength. Don't reheat it in microwave. When used keep it warm enough to make sure the glue remains completely dissolved (~60 ºC). It is better to use always a fresh solution, but you can place the glue in refrigerator for a week and reheat it when needed. But remove only as much glue as you wish to heat and dissolve in double boiler cause reheated too many times, hide glue can lose its adhesiveness.
Recipe from "Formulas for Painters" - Casein solution for panels
Sift the casein slowly into half of the water, stirring to get rid of the lumps. When smooth, add the ammonium carbonate and stir; allow the mixture to stand for an hour or more before you stir in the remaining water.
Recipe from "The Materials of the Artist"
Ammonium carbonate is dissolved in a few drops of water. The casein is first mixed with very little water, and then the rest of the moderately warm water is added.
After all the lumps have been pressed out, the solution is poured into the casein. Promptly there is effervescence; the carbonic acid escapes. After a little stirring, as soon as there is no longer any foam, the casein solution is ready.