Siccatives have two functions:
1/ In thick paint, they artificially increase the siccativity of colours with limited drying potential (which remain sticky 10 days after being applied, this is the case for reds with a base of quinacridone pigments and ivory black). Care must be taken because the paint from manufacturers already contains siccative in its formulation. This is why one should never exceed the dose of 1 drop of siccative for 1 thimbleful of colour (approx. 2 cm3). Adding too much siccative can create the opposite effect and cause cracks to appear prematurely on the painting.
2/ For those artists that make their own colours, siccatives are essential additives (added to the oil) to control the drying rate of the pigments. With age, the various paint layers will have the same hardness and the picture layer will be more uniform.
From 30 July 2002, date at which the European laws onthe labelling and sale of dangerous products changed, the lead siccative was replaced by a zirconium siccative that is much less dangerous and just as efficient.
