At the summer camp that I worked at many years ago, there were plenty of abandoned spider webs, and the Crafts director had the kids do this. But rather than spraying the background with adhesive, they carefully sprayed the web with white spray paint before immediately swooping it (while the paint was still wet) with a piece of dark-colored card stock.
I would think that spraying the background with an adhesive would make it a real dust magnet if one were to display it without a glass cover…
