- During wine production, vinegar is produced from the pomace under certain circumstances. This vinegar reacts with copper-containing materials. If this acetic acid copper solution is neutralized with quicklime, blue crystals of particularly brilliant luminosity are obtained. The pigment obtained is a luminous blue. The pigment cannot be processed with acid media or linseed oil, but it can be processed with lime, egg white and tempera. The name was chosen in memory of H. Ploss and the recipe of the blue in his book “A Book of Old Colors” (around 1500).