Styrene sheets are an excellent alternative to traditional cardboard mounts. Cardboard mounts are made of natural paper fibers. These fibers are hydroscopic. They can absorb and give off moisture in response to environmental humidity. They actually behave like sponges. This change in moisture content causes cardboard to expand and contract. When this change occurs after a print has been mounted on one side of a cardboard mount it can result in a bow or warp in the board. This effect becomes more pronounced as the size of the board is increased.
Styrene mounts have no natural fibers in them. They are not affected by variations in moisture content in the environment. They will remain stable (flat, and warp free) even when they are subjected to large changes in humidity. They are also less prone to edge and corner damage than cardboard mounts.
This is a .040" (about 3/64") white plastic sheet coated on one side with Cold-Mount® permanent pressure sensitive adhesive. This is a very smooth board. It is not hydroscopic and is not affected by changes in moisture. Changes in humidity will not cause warping.
This white plastic mount is .080" (just under 3/32") thick. It is more rigid than the thinner .040" thick styrene boards.