All driers work through the whole of the coating
Primary driers are most active at the surface where the oxygen content is the highest
Oxygen from the atmosphere is absorbed by the primary drier at the surface of the coating Solvent and MEKO evaporate
Auxiliary driers act at the surface depending on their functionality.
Calcium opens the matrix structure to facilitate solvent evaporation and deeper oxygen penetration. Free radical process started at the surface is passed down through the film. Through driers promote drying of the body of the film.
General starting point recommendations for individual metals and blends can be provided. The recommendatiosn for a coating based on standard long oil alkyd will differ from that for a short oil alkyd or a high solids coating; similarly the nature of the oil / fatty acid and any hybridisations will change the optimal drier package. The Metchem driers for alkyd based coatings are designed for ease of use, and the type of technology will determine the optimal drier package.
In order to attain maximum performance of a coating the formulator needs to find the right balance of primary, through, auxiliary driers and additives. Specific metals can provide the means for a coating to improve defined qualities; such as increased hardness, higher gloss, better through dry