I recently got a hold of a cardboard cutout of one my favorite movies and I'm wanting to convert it into an aquarium background, but my issue is that its not waterproof! Does anyone know a way to waterproof cardboard without painting over the design? I read online using waterbased paint/sprays/chemicals can cause the cardboard to warp and therefore lose its design, I've also read epoxy is a no as it turns yellow and crusty on cardboard. Anyone here artsy know of a way? If it matters its a fairly large piece that will be on a tank about 6 feet long to 2 1/2 high.