3/16" White Foamcore Board in Custom Sizes. Made to exacting standards, our foam board is a resilient, polystyrene foamcore board "sandwiched" between paper liners. The foamcore has a built-in memory, allowing it to return to its original thickness after cutting. Available in all white foamboard and all black foamboard and Colors. White foamboard has smooth, clay-coated, glossy liners.