Thanks to Qui-Gon and everyone else for their excellent advice. I just did my very first blades, and I'm very pleased with the results. I bought a 40-inch roll of clear cellophane and hung it with string from the ceiling in my basement. I rolled ~ 2 meters onto a dowel, cut it free, and shoved it onto a new white blade from TCSS. I had to reverse-roll the dowel a little to get the cellophane to "let go" of the dowel, then it slid right out. I trimmed the excess off the bottom and it's ready to use... much more evenly illuminated than the same blade empty.