What Is Foam Density?

Foam density is a specific measurement of how much weight in pounds polyurethane foam can handle per cubic foot. This density rating tells you the strength of the foam. It should not be used exclusively as a sign of durability or comfort, because firmness and lifespan of foam products like mattresses and cushions, depend on many factors, including density. Heavy density foam weighs several pounds per cubic foot, while low density foam weighs only about one pound per cubic foot.

Definition

Foam density is a rating applied to polyurethane foam, the material used in mattresses, chairs, sofas and insulation in walls. A foam's density may be based in part on the chemical composition of the polyurethane and in part on any films, paints or coverings applied to the foam.

A "heavy" or thick foam does not necessarily mean the foam will be harder to the touch--this depends on many factors, including density. Professionals may use the term "Pounds" for short, but they mean how many pounds per foot the foam weighs.Foam's density is generally expressed as low, medium or heavy.

Specific Density Information

Low density foams have about a 1.3-pound density, the lowest kind for polyurethane foam used to make cushions. This type of foam is not made for constant use and disintegrates more easily than the other types. Medium density foam has between a 1.8-pound and a 2.9-pound density, and can last for up to 6 years with proper care. Heavy density foam has a density around 2 and 3-pounds and can last for many years. Industrial types of foam can have up to a 10-pound density.

Example

To measure the density of a mattress, you can take the cubic feet of the mattress (derived by multiplying width, height, and length in feet) and divide it by how many pounds the mattress weighs as a whole (subtracting an estimation of the materials that are not foam).

Considerations

Durability depends mostly on the use of the foam. Foam in a chair that is sat on daily will have a different durability than foam that is used as insulation in an attic, even if they have the same density.

When foam is sprayed, the edges of the foam will often have a greater density than the middle area, because the foam will collapse slightly more on itself before it dries. Foam is still sprayed in a uniform density, even though the precise measurements differ slightly from place to place.

History

Polyurethane foam was created by Dr. Otto Bayer during World War II. He was looking for a substitute for rubber and similar materials to be used in manufacturing boats, planes and their accessories.