Which one among the following is commonly used as an 'anti-skinning agent' in paints ?

An anti-skinning agent is a chemical additive used in oil-based paints, varnishes, and enamels to prevent the formation of a solid layer or "skin" on the surface of the liquid during storage. This skinning occurs due to the oxidative polymerization of drying oils when exposed to oxygen in the container's headspace.

• Polyhydroxy phenols (such as hydroquinone, catechol, or guaiacol) are effective anti-skinning agents because they act as antioxidants.
• They function by inhibiting the free-radical chain reactions responsible for the oxidation and cross-linking of the paint's binder at the air-liquid interface.
• By delaying this surface oxidation, they ensure the paint remains in a usable liquid state until application.

In contrast, Gelatin is used as a binder or thickener, N-methyl pyrrolidone is a powerful solvent, and Pyridine is a basic solvent/reagent, none of which serve the specific antioxidant function required to prevent skinning.