Secondary (Auxiliaries) Driers

Secondary, or auxiliary, driers are typically clear, colorless to yellowish liquids used to promote through-dry and improve film hardness by acting as complexing agents or dispersing agents, assisting the primary driers. Key features include improving the solubility and effectiveness of primary driers, contributing to overall film cure, and reducing wrinkling. They are highly suitable for solvent-borne alkyd paints, varnishes, and enamels, where they ensure a uniform cure throughout the film thickness, leading to harder, more durable coatings. 

These driers typically work in conjunction with primary driers and are not usually used alone for drying. A significant trend is the development of more environmentally friendly secondary driers, with a strong focus on zirconium and calcium to replace older, more hazardous options like lead and potentially barium. Sub-types are differentiated by the specific metal ion, with zirconium and calcium being widely used due to their effectiveness and lower toxicity profiles.