Thompson's Stain Block Damp Seal 2.5 litreThe Thompson's Stain Block Damp Seal 2. 5L is a high performance solution designed to seal and permanently cover damp, water stains, and other household marks in just one coat. Its advanced micro porous formulation allows trapped moisture to escape while preventing stains from reappearing, making it ideal for problem areas on interior walls and ceilings. Suitable for application directly onto damp surfaces, this reliable damp seal creates the perfect