What is primer?

A primer is the first coat of paint applied to a surface before the topcoat. It acts as a bonding agent between the substrate (wall, drywall, wood, or previously painted surface) and the finish paint, ensuring better adhesion and a more uniform final appearance.

Primers are formulated differently from topcoat paints. They contain higher resin content and lower pigment levels, which helps them penetrate porous surfaces and create a stable base. Using primer matters because it reduces the number of topcoats needed, improves color accuracy, blocks stains and watermarks, and extends the life of the finish paint.

Common primer types include:

• Stain-blocking primers - designed to seal water stains, ink marks, smoke damage, and tannin bleed from wood before topcoat application.
• Bonding primers - formulated to grip glossy or difficult surfaces such as semi-gloss paint, tile, or laminate where standard primers may not adhere.
• Drywall primers - lightweight primers used on new drywall to seal the porous paper surface and ensure even topcoat coverage without blotchy absorption.

Painters in interior painting routinely select primer type based on the surface condition and desired finish. Skipping primer or using the wrong type often results in poor coverage, uneven sheen, peeling paint, or visible stains showing through the topcoat.