Ronseals Knot Block Wood Primer & Undercoat completely stops wood knots and wood resins showing through your paint. This primer and undercoat also covers bold colours, dark marks and helps your paint to stick! It makes sure you get a flawless finish that won't yellow, crack or peel. Perfect for knotty wood like pine. Guaranteed to completely block wood knots. Ready to paint over in 4 hours. Use on bare or previously painted wood. Apply this primer & undercoat from the Ronseal Knot Block range to interior, using a brush, to prepare the surface for painting. It takes 6 hours to dry and will cover up to 12 m² per litre on average.