Wilko Quick Dry Stain Blocker White primes and seals before decoration. Its a matt white paint that contains a stain inhibitor and can be applied both internally or externally over any type of paint or undercoat. It's water based formulation is effective over many types of stain including crayon, graffiti, water stains, creosote, smoke stains, hand marks, asphalt etc. and helps to prevent them from bleeding through into the top coat finishes. The contents of this can will cover 10m2* which after 1 coat, is about the same area as 6 standard doors**. *Approximate coverage depends on the surface to be painted. **Calculation based on door height of 2m x 0.8m width.