Hello! I want to cover the tops of destroyed eyeshadows palettes with resin to preserve them in all of their colorful glory. But many inexpensive palettes are made of stiff, cardboard type material. Usually with a smooth finish. Before I destroy the shadow and cover with resin, should I treat the cardboard material in any way? Some type of sealant? If so, which kind of sealant should I purchase? Thank you!