There is a product available called Seam-Sealer, made by Kenton Consumer Products, Peace Dale RI 02883. I'm using it to seal seams in Sunbrella and Herculite. It comes in a 2 oz bottle with the applicator built-in. You must apply it on the underside by inverting the bottle, so the top has to be on a table. (remember this gravity thingy)It may be available locally at a place that does canvas work for boats. (for clarification purposes: The term "boats" applies only to sailboats)