When I use liquid emulsions, I've been taping the paper to mat board, applying the emulsion, and letting them dry in empty 50 sheet paper boxes. With the highly textured watercolor papers, they've been warping, and sticking to the box top. I have no way to leave them, exposed, in the darkroom, while they dry. Any suggestions for a solution? Opening the boxes, and finding the paper stuck to the top is very disappointing. Thanks.