I'm still confused about the correct "plastic" material for making lithophanes. I realize I can just buy from CW, but in order to purchase locally, what do I need to request? I have seen some users refer to plexiglass; some to Lexan; some to "signmaker's plastic". I understand there is a difference in cast acrylic and extruded acrylic, but how do I know which I'm requesting? Do I need to go to a glass supplier and ask for one of these products? I don't want to purchase a product that will damage/destroy my bit or my machine. Please help this newbie with his confusion!

Thanks