There’s an instructable post for building an interesting kaleidoscope using first surface acrylic mirrors. The creator suggests to leave the masking in place when cutting the mirrors with a laser.
It’s my understanding that acrylic masking is either paper or vinyl plastic and I posted a recommendation to remove the masking, to avoid the chlorine danger it represents.
I’ve been unable to find a confirmation that the masking on acrylic products are vinyl.
Is there also a means of testing this sort of stuff? I recall something along the lines of heating a copper wire in a torch flame, melting a bit of the material on the wire, then reheating it to see if it turns green. Is this correct?