Tempera - priming

Cleaned, sifted, coarse-grained gypsum was spread with an adhesive solution on the board and applied to the board with a spatula. The same gypsum, diluted with more water, was applied with a brush several times and the board was left to dry for two to three days.
Further layers of mortar were made with fine gypsum. Thin gypsum (goldsmith's gypsum) was soaked in water and rubbed on the board, after rubbing it was wrapped in cloth, water was squeezed out and mixed with the glue solution used for the first primer (gypsum with glue was heated in a water bath).
The first layer of this gesso was applied with the palm of the hand to better rub in and blend with the layer of thicker gesso.
Subsequent layers were applied with a brush (up to eight times), letting the individual layers dry a bit.
After priming, everything was dried for two days. Then it was sanded with a metal blade.
Smaller boards were primed two to three times with thin plaster.
Gold flakes were sometimes applied to the gesso or chalk primer.