Ronseal One Coat Damp Seal 250ml - White Permanently blocks damp Apply direct to damp surfaces Prevents paint from flaking Ronseal damp seal brushes straight onto damp patches and permanently covers damp stains to stop them from ruining your paint. No need for preparation, it can be painted straight onto the wall. Ready to paint over in only four hours so you can do all your DIY in one day. Protects your paintwork whilst it permanently blocks and seals damp stains. Suitable for use indoors on walls & ceilings.