Shadowboxing a sort of 'bubbly' silkworm cocoon collage in a 39 x 39" frame. It was mounted in Africa, on a flat substrate that looks like thin white plastic/vinyl, which is laminated to a 1/8" masonite backer. The artist used some clear, stretchy, 'skin' to attach it. (Maybe a plastic film that's heat melted to apply?). It's coming loose in a couple of spots, so I have to re-attach the pieces. What would you use to attach a heavy silk fiber to plastic? (It's not a sheet of fabric; more like a nest, or like a bees nest, with no middle, just the walls).