Most of us appreciate some cushioning when sitting or lying on a hard surface for very long. This has been true for thousands of years, with cushions for sitting and sleeping. Mattresses began with fiber sleeping mats laid out on a floor. At some point, long cushions or pillows were made, filled with wool, straw, feathers, sawdust, horsehair—anything to soften a hard surface.
In the middle of the 19th Century, coiled springs were invented for buggy and wagon seats. Later, these coiled springs were adapted for use in mattresses, what we call the Bonnell innerspring. For most of the 20th Century, the majority of mattresses were innerspring models.
The most durable innersprings are also very firm. Mattress manufacturers cushioned this with batting, usually cotton, sometimes wool or other fibers. But with the introduction of polyurethane and foam rubber, foam began to be used for seat cushions, then as cushioning on innerspring mattresses. Various configurations were introduced, including convoluted (or “egg crate”) foam.
With manned space flight, better padding was needed to cushion astronauts against high G forces at launch. NASA contractors modified polyurethane foam to produce visco-elastic foam. This was further developed by corporate firms for consumer use, becoming memory foam.
First used for seat cushions, memory foam began to be used in pillows, mattress toppers and mattress cushioning. Eventually, all-foam mattresses were introduced, with high-density polyurethane foam as the support core. These non-spring mattresses are collectively called “specialty sleep products.”
The three major kinds of foam used in mattresses are polyurethane foam, visco-elastic memory foam, and latex foam. Each kind of foam has variations. First, there are different ingredients in these foams. Then there are different densities and firmness levels. Now gel is infused into different foams to add desired characteristics.
Foams for bedding are rated by density and Indentation Force Deflection (IFD). Density measures pounds per cubic foot. IFD measures how many pounds it takes to make a 1” indentation.
Part 2 will cover the different kinds of mattress foams
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