when my students did the mylar/playing card project, the playing card was to approximate a stiffer credit card like backing...another student entry used solar window film (silvered) but it had a lot of light transparency... perhaps a firm that mirrored storefronts could provide film with higher reflectivity, and printing company a stiffer backing from promotional plastic cards

I know everyone is enamored with petroleum jelly/cotton balls, but has anyone tried casting a cotton ball in paraffin... years ago we melted paraffin in bottle caps and added a ball of cotton..when cooled it was wrapped in foil, and fluffed to light ..

anyone ever try to make a whistle out of a cartridge case..say a 308 or 30-30?