The canvas consists of fibres that do not like contact with oil. If the oil gets into the fabric, then – over the years – the canvas in that spot simply rots and begins to fall apart.
Therefore, it is necessary to apply a new finish to the fabric, for – by decatising the store-bought canvas – we got rid of the factory finish (see the previous entry). The role of this new coating is to provide insulation against the oil from the paint, that is, block its access to the fibres. At the same time, this layer must bond well with the primer layer. Bone, or rabbit skin, glue – the same that is a component of the primer – suits this purpose perfectly.
So – after diluting it with water – is it enough to wait until the glue turns into a jelly, and paint? Not quite: this jelly is applied with a dash brush, and the excess is removed with a palette-knife. At the Olsztyn school, Tadeusz had a simple test for us all. If, after applying the primer, a single white droplet broke through to the reverse side of the canvas, it meant the sizing was bungled.
