Foam core or Foamex board is a very strong, lightweight and easily cut material used for the mounting of photographic prints, as backing in picture framing, in 3D design, and in painting. It is also in a material category referred to as "Paper-faced Foam Board". It consists of three layers — an inner layer of polystyrene clad with outer facing of either a white claycoated paper or brown kraft paper.
The surface of the regular board, like many other types of paper, is slightly acidic, for archival picture framing and art mounting purposes. However, it can be produced in a neutral, acid-free version with a buffered surface paper, in a wide range of sizes and thicknesses.
Foamex board materials are also now available with a cladding of solid styrene and other rigid plastic sheeting, some with a textured finish.
Foamex board does not adhere well to some glues, such as superglue, and certain types of paint. The foam tends to melt away and dissolve. Some glue works well in casual settings, however, the water in the glue can warp the fibers in the outer layers. Best results are typically obtained from higher-end spray adhesives. A hot glue gun can be used as a substitute, although the high viscosity of hot glues can affect finished projects in the form of board warping, bubbles, or other unsightly blemishes.
Self-adhesive foam boards, intended for art and document mounting are also available, though these can be very tricky to use properly; this is because the glue sets very fast. It is considered cheaper to buy plain foam board and then re-positionable spray mount adhesive.http://banners-printing.co.uk/