A foam mattress is a mattress without innerspring coils, the mattress is made entirely of foam. There are many types of foam on the market, but the four most popular are Polyurethane foam, Memory Foam, Gel Foam, and Latex foam.
Not all foams are created equal, there are many different qualities of foams. Foam unfortunately has a bad reputation, but this is mostly due to substandard and inferior foams dominating the retail landscape. Whenever possible, you should buy foams that are produced by reputable companies in countries that have guidelines and laws pertaining to upholstered products. Avoid imported polyurethane foams and memory/gel foams as these foams are vacuum packed and compressed before shipping.
How Foam Works
Foam is measured by density and compression: density determines the strength of the foam, and compression determines whether foam is soft or hard.
Foam density is measured by the mass of the foam per unit volume (The weight of the foam is divided by it’s dimensions in feet, the result is the measurement by cubic foot.): the denser the foam the more weight it supports. The more support the foam gives the body, the more that foam will provide ‘push back’ against weight. That’s why high-density foams are more expensive: they provide constant and even support for many years. In the mattress industry, .09lbs/ft3 to 1.5lbs/ft3 foams are considered ‘low density’-1.6lbs/ft3 to 1.9lbs/ft3 is considered ‘medium density- and 2.0lbs/ft3 to 3.5lbs/ft3 is considered high density. (Specialty foams such as memory, gel and latex can go as high as 6lbs/ft3 density but only because their chemical compositions differ than that of polyurethane foams; as such, their quality should not be measured against that of polyurethane foam. For example, a 2.5lbs/ft3 memory foam is considered a low density foam but a 2.5lbs/ft3 polyurethane foam is considered high density.)
Compression determines the comfort, or firmness, of the foam. Compression is measure by Indentation Force Deflection, or IFD. The IFD test method determines the load bearing capacity (firmness or stiffness), and is expressed in pounds force per 50 in.2 at a given percent deflection of the foam.
For example: a foam with a 50 IFD has a target IFD of 50 lbs/50 in2 at a deflection depth of 25% of the original thickness of the sample after a rest period of one minute.
To obtain the 25%R value, a 50 in.2 circular indenter is driven into a 15” x 15” x 4” foam sample, stopping when it reaches a deflection of 1”, or 25% of the 4-inch thickness. The testing device records the force in pounds required to hold this foam indented after one minute: the higher the force reading, the higher the load bearing capacity of the foam.
Sag Factor (Modulus) is the ratio of the 65%R IFD to the 25%R IFD values and is expressed in real numbers with one decimal. Sag factor gives an indication of cushioning quality. A high value indicates a resistance to “bottoming out.”
Recovery Ratio is the ratio of 25%R IFD released to 25%R IYD initial when measuring IFD values at 25% deflection, 65% deflection, and then released back to 25% deflection. Recovery ratio is expressed as a percentage.
Another measure of compression is Compression Load Deflection, or CFD. CLD is also a measure of firmness and is expressed in pounds per square inch (psi), at a given percentage deflection.
The sample size is 2” x 2” x 1” thick. The entire sample is compressed under the 50 in2 indenter in this test. The procedure is the same as IFD.
Making polyurethane foam is complicated business. Flexible polyurethane foam is a polymer that retains its resilience. The three main ingredients in quality polyurethane foam are Polyol, Iconycates, and water. Other blowing agents and catalysts can be mixed into the foam at the liquid stage to change or enhance comfort levels. All polyurethane foam manufactured in Canada is regulated by law and free of CFCs, polybrominated diphenyl ethers, formaldehyde, and phthalates. High quality polyurethane foams manufactured in Canada also have an opened cel structure, which allows for increased air circulation. Foams with opened cel structures will not heat up, or cause the sleeper to heat up in bed.
The technical name for memory foam is visco-elastic polyurethane foam. Visco elastic memory foam is a polyurethane foam to which they add gas into the polymer matrix that increases the viscosity and density of the foam. Memory foam is temperature sensitive meaning that it will harden in cold temperatures and soften as it warms up. Memory foam is slow in recovery, which can sometimes leave the sleeper feeling ‘trapped’ or ‘stuck’ in the mattress making movement while sleeping difficult. Faster recovery memory foams are now available.
NASA developed memory foam in 1966 for use in the astronaut’s seat cushions. When buying memory foam, make sure it’s an opened cel foam structure, which helps air circulation; however, memory foam still does retain heat for two main reasons: it is temperature sensitive, and, because of the nature of the foam, the sleeper will sink into the foam causing the underside of your body to be ‘covered’ by the foam. Some people enjoy the heat, especially those with medical conditions that find relief when heat is applied to a specific area of their bodies. Combining memory foam with coils will help air circulation and lessen heat build up significantly.
Buy memory foam manufactured in Canada whenever possible. Imported memory foam mattresses and pillows are filled with VOCs and carcinogenic chemicals.
A gel foam is a viscoelastic memory foam that is infused with gel beads or a gel liquid that’s poured into the foam’s polymer matrix at the primary stage. Gel foam was invented to address the issue of heat build up in traditional memory foam. The gel acts as a Phase-Change Material, which, in theory, is supposed to dissipate heat away from the body thereby reducing the sensation of ‘sleeping hot’. The gel itself is derived mostly from collagens and water. Since gel foam is new to the market, tests regarding heat build up are few; however, recent tests indicate that the gel ingredient itself does nothing to dissipate heat, the reduction in heat comes from the fact that gel foam has an opened cel structure, which allows for better air circulation: it’s the air that cools you down, not the gel.
Latex foam is made from the milk/sap of a rubber tree. Like maple syrup, the milk is collected, poured into molds, and cooked in ovens where the latex is solidified. The transformation from liquid latex into mattresses and pillows is complex: To create foam latex, a liquid latex base is mixed with various additives and whipped into foam, then poured or injected into a mold, and baked in an oven to cure. The main components of latex foam are the natural latex base, a foaming agent (to help it whip into a froth), a gelling agent (to convert the liquid foam into a gel), and a curing agent (to turn the gelled foam latex into a solid when baked).
Dunlop and Talalay Process
A process developed in 1929, the latex sap is whipped into a froth state, poured into molds and steam baked. While the liquid latex sits in the oven, the sediments in the latex settle at the bottom of the liquid, making the finished latex foam slightly firmer on the bottom than the top.
There are two ways to manufacture latex: The Dunlop Process and the Talalay Process. It’s important to understand that Dunlop and Talalay are NOT two different types of latex, rather, it’s the manufacturing process that’s different; both are good.