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HOW TO CHOOSE
THE RIGHT
FOAM FOR THE JOB
POLYURETHANE FOAM is made by forcing a blowing agent (a gas or volatile liquid) into a liquid plastic. The gas forms "bubbles" in the plastic, which create a breathable cellular structure when the foam hardens. About a dozen chemicals are used in the process but the foam itself is inert and hypoallergenic when cured. Poly-foam manufacturers no longer use CFCs (chlorofluorocarbons).
Manufacturing is done in huge quantities. A manufacturer pours up to 1200 feet by 82 inches by 36 inches at a time of one kind of foam. This is sliced into slabs or shapes for seating, bedding, and all kinds of padding. Wedges, blocks, cylinder, and die-cut or computer-cut shapes are available.
Poly-foam is identified by a two-part numbering system. One two digit number will indicate the weight of the foam. 0.9-1.2 lbs/cubic ft. is light density foam, 1.3-1.5 lbs/cubic ft. is medium density, and 1.8-2.7 lbs/cubic ft. is high density. Generally, the heavier the foam, the more it costs, and the longer it lasts. As an example 1.8 lbs/cubic ft. foam is written 18.
The other number (ILD) indicates the stiffness of a foam. The higher this number the harder the foam. The lowest number, 10, means it takes ten pounds of pressure to compress the foam. The highest number is 110. The combination of weight and stiffness creates the longevity and usefulness of the foam.
A good high density, firm foam for mattresses and high use seating would be numbered 3525 (35ILD/2.5 wt.) and could last 8-10 years. A medium density, firm foam for camper cushions and kids beds might be 16545 and could last the same 7-8 years with light use.
Polyurethane foam discolors with age but this does not effect the usefulness of the foam. Dogs and small children like to chew on foam and many foams are easily torn. A protective cover is recommended.
Most bed or cushion foam is open-celled foam and is comfortable to sit or sleep on because it "breathes". A closed cell foam doesn't breathe or absorb water. It floats, and is good for exterior use. Examples of closed-cell foams and uses are EVA (tennis shoe soles), XPE (floating hot tub covers), Airex (boat cockpit cushions), ethylene(bubble pack), and polystyrene (Styrofoam).
LATEX foams are made of actual rubber from rubber trees in the tropics. They are made in much smaller molds than poly-foams, usually standard mattress sizes or smaller. Thickness is limited to 5.75" for mattresses and 4"-4.75" for cushion stock. The price for latex is slightly higher than good polyurethane but latex will last more than twice as long. It also feels much more luxurious than urethane. Latex is an "organic" foam and dries out with age; high heat accelerates its deterioration. Used as a mattress on a platform it feels like a box spring and mattress combination.
