Can't be the indoor light... I can see through this stuff in the dark! Certainly nothing like the opacity of all the white rolls of ultracoat I've used. What really pisses me off is you can't tell until a piece is cut out and the white backing is peeled off. I really hate to use Monokote anymore, but I don't see a choice. I just wish I knew before I blew the 14 bucks on a roll that's not fit for the underside of a wing