: polethelene foam is often used by shippers to package delicate parts and is
: much cheaper than minicell (EVA) foam. it, too, is available in several
: colors and densities whith white (Natural) being the cheapest and most
: available.

Polyethylene foam, such as Dow Ethafoam is commonly available in desities of 2, 4 and 9 pounds per cubic foot. I believe it is also available in a density around 1.3 pounds as well. The standard color for all of these is white, though some foams are available in colors as well. I don't know believe there is an industy-standard color coding scheme, as I have see similar density poly foams in white, yellow, pink, lt. blue, lt. green and black.

We used the 2 & 4 pound densities extensively in the indoor archery range I used to own. The 2 pound foam is light and flexible, but not very durable. If used for an application where it is compressed (such as knee/thigh pads), it quickly breaks down. It will also absorb water along cut edges where the foam has no 'skin' on it. The 4 pound foam is heavier, pretty stiff and it can be used for structural purposes. It has smaller cells and handles pressure much better. The 9 pound foam is pretty heavy, very stiff and hard as a rock. I cannot think of any application for it in kayak building.