OT: Why are floodlamp gels gel ?

If the colour came off, it wasn't really a proper theatrical colour filter. The name gel stems back to a time when colour was made from a coloured gelatin based liquid poured out into a flat tray and left to set. they were thick and unstable, prone to fading, shattering and catching fire.

Later on, filters (theatrical types just call it colour) were made from an acetate material which didn't handle the heat very well, This was known as Cinemoid, also prone to fading and melting. These days, proper theatrical colour filters are made with a very complex process involving two or more layers of polyester and polycarbonate. They still burn out, specially blue! Darker greens wrinkle up for some some reason.

There is some very interesting reading on the Rosco and the Lee Filters websites

Ron

whatever

sheet

same

These came from a set of gels (as they called them) for theatrical floodlights, that I salvaged for the coloured material , when they got replaced with a whole new range of lights. Nothing wrong with them , not even crinkled. Seem to be a clear plastic core with a coating of couloured something , each side, that easily dissolves off with meths, which I did not expect.

Only ones I see are distributed by Lee Electrics in the UK - for film and TV, etc use. They are coloured throughout.