Blue Foam, Pink Foam and Foam Board

• Foamboard
  Foamboard is a superb building model material that consists of a thin sheet of foam sandwiched by two layers of paper (or other laminate). The result is a very lightweight but stiff section of material that can be cut cleanly with a sharp knife yet remains durable and rigid.
  Foamboard is commonly called “Fome-Cor” (or Foam-Core) as well as a variety of other tradenames and generally comes in thicknesses of 3mm and 5mm.
  

• Blue/Pink foam
  The “Holy Grail” of modeling: you can do almost everything with this material. Lightweight, tough, durable, ideal for crafting terrain such a hills and cliffs, making gaming boards, even buildings and bases. It doesn’t warp, is relatively light and can be worked easily with a hot-wire cutter, hot-knife, sawn and even cut with a sharp knife. When heated and even when sanded vigorously these materials will give off toxic and noxious fumes. As such always wear a fume-mask or work somewhere very well ventilated. Breathing in the powder after sanding is also a hazard.
  People have terrific difficulty getting hold of these materials almost entirely because of them traditionally being called “Pink or Blue Foam” which is, sadly, now an obsolete term.
  Pink/Blue foam is actually EXTRUDED Polystyrene. This is a closed-cell extruded form of polystyrene that is commonly known by the trade name of “Styrofoam”. Just as most people call a vacuum-cleaner a “Hoover” Extruded Polystyrene is called “Styrofoam”.
  
  Now Styrofoam comes in many guises, it comes in different colours and different thicknesses and different densities. Colour can be largely ignored – it isn’t important anymore and very few of the companies that can supply Styrofoam will even know what you mean by “Pink or Blue Foam”. If you see foam that is blue or pink it can easily be something completely different and totally useless: what you need to know about is Density.
  The density of Styrofoam for the modeller essentially means how “hard” it is: the denser the foam the harder (and heavier) it is. The original (blue) Styrofoam has a density of 32kg/m3 and this forms the benchmark for modeling: anything less dense than this can be too soft, anything more dense can be fine... right up to 200kg/m3 foam which is used to make surfboard blanks!
  
  To find the right foam near to you search Google for “Styrofoam” or “Underfloor Insulation” and find a local stockist – Phone them up and check the density of the styrofoam, forget the colour and don’t worry about the tradename it is sold as. Here are a few trade names that may help you locate a supplier though:
  Styrofoam LBX / DOW Styrofoam IB (UK/USA/Eur/Aus/NZ)
  Floormate (UK)
  Foamular (USA/Oz)
  Styrodur (Europe)
  Roofmate (France)
  De-Q-cell (Germany

• If you want to buy blue foam (Styrofoam) then we sell A4 sheets of it here: styrofoam (blue foam) and foamboard.
• WARNING - styrofoam and all other extruded polystyrene sheets are capable of giving off toxic fumes when heated. That heating can be achieved when hot-wire cutting, vigorously sanding (even by hand) and also by application of hot glue. The fumes given off are of a serious toxic nature (Hydrogen halides) and as such styrofoam's should never be worked in an enclosed environment or without wearing a graded fume-mask with a filter capable of removing the appropriate fumes or preventing their inhalation.
• Remember that Polystyrene, the plastic from which Styrofoam is made, has a glass transition temperature of almost exactly 212 Fahrenheit (100 Celsius). Temperatures of around boiling water can start to produce unwanted side effects such as melting and production of fumes. Cutting styrofoam by electric saw will also melt and produce fumes.
• Always use appropriate glues such as UHU Por or Foam-2-Foam to stick styrofoam together.
  White or yellow emulsion glues such as PVA (elmers) and aliphatic resin (wood glue) will only stick styrofoam where they have contact with the air, where air cannot reach the glue then the glue will NOT set and remain liquid.
  Glues such as "No More Nails" (which I think is also known as Gorilla glue in the USA) will also not set where air cannot reach them. (remember that some styrofoams are NOT air-permeable and some are - this changes from brand to brand and individual density and thickness of the sheets. On the whole styrofoam that is dense enough to be used for war game terrain making is NOT air-permeable and is thus not suited to being glued with air-dry glues. You will need to experiment with your own local type of styrofoam to discover whether or not such air-dry glues will work though - do not rely on seeing if the glue has dried at the edges; instead take two small sections about 200mm x 200mm and glue them flat one on top of the other. Leave for 24 hours and then pry apart the two sheets - if the glue is still liquid in the center of the sheets then you know that you should not use that glue as it will never set))
• Dust produced when sanding or cutting styrofoams with a saw are also hazardous and should be avoided by wearing a dust mask and using appropriate ventilation and other safety measures.
• The safe maximum use temperature of styrofoam is 75 degrees Celsius.

The image below shows Foam Board often known as Fome-cor, Foam-core and a variety of other trade names. Thickness are usually 3mm and 5mm

The next image shows EXPANDED polystyrene which is most often found as a packaging material. It is lightweight but very flimsy.

This next image shows Blue Foam, aka Pink Foam, Aka EXTRUDED Polystyrene.
It is often called "styrofoam" although "Styrofoam" is actually a trade name of DOW extruded polystyrene.