Latex Mattress 101
Latex mattresses do not currently make up a huge segment of the market, but they are growing in popularity. Latex refers to a stable emulsion of polymer microparticles in a liquid medium, and may be made in the lab or come from the sap of several types of tree. It also occurs naturally in lettuce, dandelion, and poppies, though these types of plants aren't used for rubber production. The biggest commercial source of natural rubber latex is the rubber tree.
To make the latex used in mattresses, the material must be turned into foam rubber. This is often done via the Talalay process, in which a liquid natural latex bases is placed in a closed mold containing no air. The mold is frozen and carbon dioxide gas is added to produced the foam cells. The mold is then heated, and the rubber is cured. The similar Dunlop process uses a centrifuge and does not freeze the mold. It's a less expensive foam, but has less consistent texture and may use more chemical additives during production. Dunlop process foams are generally denser.
This kind of rubber is marketed as a healthier option to people who have concerns about the safety of petroleum based foams like polyurethane foam and memory foam. Unlike petroleum based foams, natural latex foam rubber does not give off VOCs (volatile organic compounds) as it ages.
While Talalay process foams are made from natural rubber, they may not be organic or completely natural, as often advertised. This is because some curing agents are also required in the process, and liquid rubber is often stabilized with ammonia. Depending on the curing agent, the rubber will not be completely natural. However, the product is a great deal more natural than many completely artifical foams.
Foam rubber manufactuers can produce a number of different types of foam rubber in varying densities and with different softnesses. The Talalay process particularly makes latex foam production very easy to control. Mattresses made entirely of this foam may be rolled up for storage, though they should not be compressed as long or left in areas with high temperatures. Talalay latex foam is more resilient than Dunlop process latex foam or other types. If a mattress is left rolled too long, it may not recover when unwrapped and may not work properly.
Not all latexes are the same. Some are made from natural latex, while others use a synthetic latex, or a blend of natural and synthetic materials. The origin of the latex used in a mattress is unlikely to affects the way it feels (though some people report that both types are more durable and comfortable) but it does affect the product's environmental footprint. People purchasing latex mattresses because of ecological concerns should take care to find a latex mattress produced using naturally sourced materials.
Latex mattresses can range from 10lb ILD to more than 40lb ILD. Natural latex provides many of the same sleep properties as conventional visco-elastic memory foam. It reacts to the weight and heat of the body and conforms to its contours. This material also resists infestation by dust mites and reduces the risk of mildew. Allergy sufferers who do not have a sensitivity to latex may find that this foam reduces the frequency and strength of reactions compared to conventional mattresses. However, people with latex sensitivities must avoid this foam, as it can cause irritation, itching, and other unpleasant reactions.
Natural latex is said to sleep "cooler" than synthetic latexes - it supposedly retains less heat over the course of the night. This is also affected by the size of the foam cells, however. Larger cells encourage more air circulation and a cooler mattress. Latex also resists packing down and formation of body impressions.
Latex beds are available in many different varieties. Some are solid latex foam, while others are made of multiple zones and even incorporate innersprings. Multiple layer mattresses may also use latex from different processes on the top and bottom to provide the ideal feel. Dunlop latex on the bottom of a mattress gives it firm support, while Talalay latex on the top provides a softer feel while you sleep. The best mattresses will offer a long warranty with a full replacement guarantee.