I've experimented with some fibreglass resin and also some car body filler on the inside of my styrene helmet. I put a 2" square of each on the inside just to test whether they'd eat right through or whatever. Well, they both set great and looked like they were adhering well, but the car body filler came off when I flexed the helmet and the resin also lifts off when I gently tested it with a knife blade.
On the positive side, there wasn't any sign of damage to the styrene. I guess for a helmet it'd be OK if the entire inside is coated, but for something like the gauntlets it looks like it will flake off with normal flexing. The car body filer contains styrene, so I figured it'd really grab on, but it acted like the styrene had mould release on. I put both samples onto the shiny side of the styrene - could that be the problem?
Any advice, folks, please?