There are a few key things you need to know about memory foam mattresses before you consider purchasing one.
Memory foam was originally desgined by NASA in the 1970's to make the lift-off more comfortable for their astronauts.
With the pressure of the g-forces the astronaut's body was pressed firmly into the foam. The material was able to conform to the shape of the astronaut's body offering excellent support and actually reducing the effect of the g-forces.
When the pressure was removed the foam would bounce back into place. It wasn't long before people started thinking about memory foam mattresses and the benefits that this material could have on sleep. In 1992 a Swedish company called Tempurpedic brought the first memory foam mattress to North America. The popularity of this new material has grown rapidly and now everybody wants to know about memory foam mattresses.
When you put pressure on a non memory foam mattress the desire of the mattress is to spring back to its original shape. The exact points where you put the pressure on take your weight, give you support but also fight back. The rest of the mattress does nothing.
Memory foam cells have holes in them. When there is no pressure being applied these holes are filled with air. When pressure is applied the cells are compressed and the air is squeezed into adjoining cells. What this does is spread the load across more cells, not just the cells you are lying on. This means more of the mattress is taking your weight and isn't fighting to regain its shape so aggresively. This is what makes memory foam so comfortable.
When you get up from a memory foam mattress it will hold your shape for a period of time. This is because the air returns to the compressed cells. Very soon the entire mattress returns to an even form. This is unique about memory foam mattresses and it is its biggest drawcard.
Density: The density of memory foam refers to how many pounds there are per square foot of mattress. Low quality products have densities of 2-3 lbs and medium quality of 3-5 lbs. High quality mattresses have a density of 5 lbs or more.
Density isn't relevant to firmness or comfort but rather it is relevant to durability. The denser it is the more durable it will be.
Thickness: Memory foam is not suitable as a mattress material on its own. It should only be the top layer and needs some form of base to be attached to, preferably latex foam. Don't bother with memory foam that is less than 2 inches thick. 2 inches should be the minimum you look for and higher quality mattresses will have 3 inches.
Tempurpedic and all other memory foam producers use foam that is derived from petrochemicals. This artifical foam is known for trapping heat, making sleep uncomfortable and releasing its toxic gases into your bedroom.
Essentia, a Canadian company, has developed the ability to create natural memory foam. Natural memory foam is really natural latex that has been processed to have the feel of memory foam rather than the feel of a regular latex mattress. This is instead of visoo-elastic foam which is what true memory foam is made out of.
They harvest natural latex from the hevea tree and mix it will essential oils, plant extracts and water to create a healthy and non-toxic memory foam. Natural memory foam works in the same way as the regular stuff and has all the same benefits regarding comfort and support, despite actually being made from natural latex.
The advantage is that with natural memory foam you do not expose yourself to the myriad of toxic chemicals that are in regular foam and it the mattress keeps cool.