Stain block

Stains on emulsion paintwork often bleed through when painted over, and repeated coats of emulsion fail to block them. Any of the following can stop this happening them:

• dilute PVA
• a coat of oil based non-gloss paint, such as undercoat or eggshell
• Stain block paint

Usually one coat is enough, but not always. The very worst stains can require alternating coats of emulsion and oil paint of stain block. Since oil paint is slow drying, stain block is then preferable.