Why are lines visible in my layers of Polyester Casting Resin? Monica P. February 26, 2020 16:51 Updated Layers were allowed to cure for too long; Layers should be gelled not hard when additional layers are added. Related articles How do I post cure a Mold? EasyCast Resin Knobs by Marie Browning Which silicone do you recommend for doing large molds? Resin Cell Painting Comments 0 comments Article is closed for comments.