I have a very large (16'x20') piece of canvas that is hanging from a wooden frame in a wavy pattern. I need to make this fairly rigid...so I assume that some sort of spray could accomplish this (preferably something available from Lowes or Home Depot). I thought about maybe spray polyurethane or some specific type of spray glue, but hoped that someone else has run into this before and could suggest the least expensive (and maybe low fumes?) way to make my fabric rigid without taking it down. Thanks!