CottonProof wash-in or paint-on treatment adds water repellency to cotton, heavy duty canvas and poly-cotton fabrics. It contains a high concentration of active ingredients that make it highly effective on clothing and gear that typically offer minimum protection from the elements. It works great on everything from barn coats and duffel bags to outdoor clothing and tents. Can be diluted with water and sprayed or painted on wet or dry cotton or canvas tents.