Cobalt siccative is a mixture of cobalt salts and mineral essences. It is used in oil paint to speed drying and is particularly suitable for slow-drying paints. For this purpose, it is used in small proportions, from 1% to 5%.
Its action is fast and powerful. If used in excess, it can cause cracks, wrinkles, and darken the paint. For this reason, it is primarily used by professionals, but with the right precautions, it can also be used by beginners.
The siccative can be diluted with turpentine, petroleum spirit, or other mineral essences.