The Ronseal One Coat Stain Block can be used before painting to permanently block stains from showing through. It covers nicotine, crayon, grease and much more. Permanently blocks stains in 1 coat and is ready to paint over in 4 hours Before you start, make sure you're in a warm well ventilated room. All surfaces should be clean, dry and free from dust. Mask any surrounding surfaces and repair any holes or cracks will the correct filler. Stir well before you start. If you're using it to seal bare surfaces then thin with 20% water. Put the paint on with a brush or a roller. Leave it for 4 hours before painting or wallpapering. Clean all brushes and rollers in warm, soapy water. Coverage: 8m² Per litre.Usage Areas: All interior walls and ceilings. Compatibility: Bare or previously painted walls and ceilings.