Foam is really all about DENSITY and COMPRESSION

Density is a measurement of the mass per unit volume and it is expressed in pounds per cubic foot. Basically, it is the weight of a cubic foot of foam (12” x 12” x 12” ÷ 144 = 1 cu. ft). Density is not a measure of firmness or softness in polyurethane foam, but is important to the type of usage it will receive. To put it simply, the higher the density, the longer the product will last.

Compression is expressed in the industry as IFD (Indentation Force Deflection) also known as ILD (Indentation Load Deflection). This unit of measure expresses the degree of firmness or softness. The IFD/ILD is not an indication of foam quality or density. To put it simply, the higher the ILD, the firmer the foam.

Densities range from less than 1-lb/cubic foot to over 6-lbs/cubic foot and compressions (ILD/IFD) range from 3 ILD to 150 ILD.

A combination of different densities and compressions make up a variety of different foam grades. An illustration of how to determine the density and compression for any given grade of foam is as follows:

Grade 1130 = 1.1 Density and 30 ILD : Lower density and ILD = Shorter product life and softer

Grade 2250 = 2.2 Density and 50 ILD : Higher density and ILD = Longer product life and firmer

The support factor in a grade of foam is probably the most important measure because this dictates how much weight or load factor the foam will support. The support factor is largely dependent on the foam compression (or ILD) and the foam density. It is calculated by performing a specific test that compresses the foam, first at 25% and then at 65%.  These compression readings (also known as PSI) are divided to come up with the support factor for the foam.  In simple terms, the higher the support factor, the better quality the foam is. HR (High Resiliency) foams are most likely to have the highest support factor.