Acid-Free Foam Boards. Pack of 15. Thickness: 3/16 inches. Inner foam core color matches exterior color. Foam boards are extruded polystyrene foam laminated between two sheets of paper to form a lightweight but strong and rigid surface. Features a smooth surface on each side board. Our lightweight and rigid foam boards resist warping and bending. Smooth surface can be used for screen printing, painting, mounting. Foam boards are ideal for presentations, signs, crafts, and art & science projects.