Essential base for durable exterior finishes. Ensure optimal protection and longevity for your wood and metal surfaces with this premium primer undercoat. Designed to be the ideal foundation for all Sandtex exterior gloss and satin paints, it delivers guaranteed results. Sandtex primer undercoat is a solvent based flexible base coat for Sandtex solvent based trim paints for exterior wood and metal. Apply this primer & undercoat from Sandtex to exterior, using a brush, to prepare the surface for painting.