In the early 1970's, NASA's Ames Research Center funded a development project designed to create a substance that could help relieve astronauts of the incredible g-forces experienced during lift-off.  They believed that one of the key secrets to reducing g-forces on the body was to use a foam material that could conform to each person's shape and hold this conformity.  While a foam mold of each astronaut's body shape could accomplish this, any movement would take a person out of this position and create incorrect pressure points against the body.  Instead, they created a new foam material that was visco-elastic and therefore able to conform to a person's shape, but then come back to a normal shape once pressure was removed from the foam.  This could allow an even distribution of pressure or body weight over the entire surface of the foam, but quickly adapt to any movements of the body.

With this amazing discovery, Fagerdala World Foams of Sweden, one of Europe's largest foam producing companies, began experiments in the 1980s to perfect it for consumer use. 

In 1991, the Tempur-Pedic®, a Swedish Mattress company introduced this material in a mattress form to the people of Sweden with very well-received results.  In 1992, Tempur-Pedic® launched the same products in North America and experienced a similar response.

With the success of Tempur-Pedic®, other foam manufacturers in Canada and the United States began to develop their own visco-elastic memory foam material to offer mattress, upholstering and specialty product companies the ability to allow consumers to have a variety of options and price levels to choose from.

The differences will be outlined in the following paragraphs and hopefully enable the consumer to make an informed and savvy decision about which foam mattress product best suits their particular needs.

What Makes Foam have Memory

To give a piece of foam memory, you start with a synthetic polyurethane foam material and add certain types of chemicals which add an increase in weight or density to the foam.  With the addition of these chemicals, a non-toxic, visco-elastic foam material is created.  Visco-elastic can be synonymous with memory foam or some like to refer to this as "viscoelastic memory foam."  However, there are many features along the way that will help determine what type of memory foam you end up with.   To understand exactly what differences are found in each final product, you first have to start with understanding how to grade each foam. 

How Foam is Graded

For a material to be visco-elastic, it will have to be temperature sensitive and have an ability to rebound fairly quickly and return to its normal shape.  Memory foam is graded by its visco-elastic nature and its durability by breaking it down into the following grading system:

1. Weight (Density in pounds per square foot):

    The weight of a foam is determined by the amount of chemicals used in the composition of the polyurethane foam.  The more chemicals, the higher the density and the more visco-elastic it will become.  This density will not determine the hardness of the material, this is done through utilizing the ILD rating structure.  Many memory foam mattresses use a 4 and 5lb. density, but some use as low as 2 and 3lb. densities.

2. ILD Rating (Indentation Load Deflection):

    The ILD rating is going to tell you how hard or soft a material is.  The 25% ILD rating is the number of pounds required to achieve a 25% compression of a 4" thick foam using a 50 square inch indentation. An Example of this is as follows: 20lb. ILD foam indicates that this material took 20 lbs. of pressure to indent this foam 25%.  Keep in mind that the higher the ILD, the firmer the foam.  This rating is synonymous with the abbreviation IFD (Indentation Force Deflection).  IFD is still in use, even though ILD was created just for the purposes of grading polyurethane foam.  You can assume that a lower ILD for the top layer of your memory foam mattress or bed topper can be a real advantage in pressure point reduction.  However, too soft of an ILD or too thick of a very soft surface layer, especially without enough support underneath, can sometimes be problematic for low back sufferers.  That is why the best memory foam mattresses use a layered effect that properly offers a supple enough surface to disburse pressure points, but gradually firms up in the layers below, with a very resilient support base used in the final layer.

3. Resilience:

    This measures the foam's springiness by determining the percent rebound of a steel ball dropped from a height of 36". The term "H.R" (high resilient) foam refers to a highly resilient foam that will give a very high "ball rebound" reading.  In general, the higher the resiliency, the better the more durable the foam will be with compression forces.  However, with viscoelastic memory foam, less resilience indicates a better force dampening.  This is due to less rebound pressure fighting the force of your body as it sinks into the mattress.  Very high quality memory foam mattresses combine lower high resilient layer(s) with memory foam on the surface, so you get the pressure point reduction, while retaining the extra support below.

4. Tensile:

    This indicates the extent to which foam can be stretched, measured in pounds per square inch, and how much elongation in terms of percent of stretch before rupture.  This value has little relevance to memory foam mattresses because they are not usually stretched, and will become compressed only when slept on. 

* It is important to remember that these ratings can vary from each foam batch that is poured and that no mattress company can predict an exact rating on their mattress each time they produce the final product.  As an example, a 10 ILD rated foam could vary from 8 - 12 ILD each time the foam is poured. 

 What is the initial smell that comes from memory foam?

While the memory foam that comes from the U.S. does not contain toxic ingredients such as formaldehyde or PBDE (polybrominateddiphenylether), it can have somewhat of a new foam type of smell that can stay for a couple of days to a couple of weeks, depending on the foam manufacturer. While this smell does not seem to trigger allergies, it can be a bother initially for people who have sensitivity to smells.  If you do experience this, here are some tips to help the smell go away quicker.  Air out the room and wash the sheets after the first couple of nights sleeping on the mattress.  Sometimes a dish of vinegar on the night stand can help nullify the odors.  An ozonator machine will rectify the situation very quickly.  However, if you are worried about the initial smell, there is a new technology memory foam called Biogreen® which has been shown to be free of the initial off-gassing smell produced.

What about organic or green memory foam?

One new trend in all bedding is to speak about organic memory foam or green memory foam.  While there are ways to make memory foam more environmentally friendly (Biogreen® Memory Foam is one such example), for memory foam to have the same type of visco-elastic feel and support as the original NASA developed formulation, it cannot be organic, soy based (usually 5 - 10 % soy can be added to memory foam), nor can it be all-natural.  However, the memory foam made in the United States has been shown to be safe and non-toxic and some manufacturers have gone one step further to reduce or eliminate V.O.C. off-gassing odors and other borderline chemical additives.

What to look for in a good quality memory foam mattress

Obviously it will be important to allow the foam to do what it is best for:  Allowing for a better contouring of your body shape and therefore less pressure placed on the areas of your body that press harder against the bed.  However, don't just go by your weight, because if you are tall, then your weight is dispersed over the bed more.

A good memory foam mattress will not need a box spring underneath it to make the mattress feel good.  You can order a platform base to increase the height of the bed, but remember that this mattress should feel good if it was placed on an even, concrete surface.  A good way to test the surface of a box spring or box foundation is to sit or even stand on various areas and see if it compresses underneath you.  If you have an existing foundation that is weak, you can easily place two cut 3/4 to 1 inch thick plywood sheets over it to give it the necessary support.

Also, you may want to look at the warranty that a company offers, because you can then worry less about spending extra money for a higher weighted mattress and can attempt to get the correct mattress feel, but save on cost. 

What is the difference between Tempur-Pedic memory foam and other Memory foam Mattresses?

A Tempur-Pedic mattress original mattress is eight inches thick and has two layers.  The top layer is composed of three inches of a 5.3 lb. visco-elastic foam that has a listed ILD rating of 14.  The bottom layer of the mattress is composed of 5 inches of 3.5lb., non-visco elastic, High density polyurethane.  It includes a cover that is composed of a soft, cotton-like material that is stretchable.  To prevent voiding the warranty, Tempurpedic mandates that their foundation be purchased with their mattress. 

Tempur-Pedic now offers a Tempur-HD, a 7.0lb. density memory foam that is more temperature sensitive.  It will feel firmer until it adapts to your body temperature, especially in cooler room environments.  At the end of 2009, they came out with the Cloud Supreme mattress, which utilizes the same multi-density, memory foam layer design of the Tri-Pedic, a mattress that came out from Selectabed.com in 2002.  Both mattresses utilize 2 inches of 4lb. density memory foam foam that is bonded to 2 inches of a 5lb. density memory foam.  The reason for the 4lb. density is to offer a less temperature sensitive and more plush initial feel.

Other companies are now offering a two layer 3lb.- 8lb. visco-elastic material and some even offer other types of materials that are layered throughout the mattress.   They also offer a wide variety of ILD ratings, but the most common are 8-20.  They are using everything from the thinner cotton and/or Bamboo-type cover, to a more bulky wool or quilted cover.  While these bulkier covers will feel softer to the touch, the disadvantages are that they will take away form the memory foam feel and contouring of the body.  Wool covers will be warmer in the winter and hotter in the summer.  The cotton type of covers can wick away moisture, but you may want to get an easily removable one, so you can wash it every so often.  They offer thinner and thicker sizes, but eight to 10 inches usually suffices.  If you have a solid platform base already, then it is not necessary to order one at the time you make your purchase.  However, you may need to order one if you loose integrity in your base down the line.

With all of this said, perhaps the biggest reason many consumers choose to go with a different mattress company would be price.  While Tempur-Pedic® is not the most expensive out there, there are companies offering memory foam mattresses at significant price reductions.

You can browse through a list of mattress companies who offer Memory Foam Mattresses, mattress pads, and other similar products by clicking here.

Spring Mattresses Vs. Foam Mattresses

While a spring mattress was the standard for many decades,  foam mattresses are becoming more and more popular due to their unsurpassed comfort and overall body support.  While spring mattresses can feel nice to sit or lay on, they will not offer anywhere close to the body contouring and therefore spinal support that memory or latex foam can offer.  There is always fiber and some type of foam over the springs, but these coils will actually cause a trampoline effect and bend inward when pressure is applied without conforming to the specific bumps and curves of the body.  While foam can shrink over time, springs can bend and lose their shape over time.  Therefore, an old foam bed will likely feel better and offer better support than an old spring mattress.

Memory Vs. Latex Foam

Latex foam has a higher elasticity or resiliency than memory foam.  The result is that latex will feel more springy and memory foam will feel more solid.  Therefore, Memory foam will not push back up against your body upon pressure being applied to it.  Many mattress companies are using both of these two materials to blend the perfect mattress combination.  Rare allergies to latex can be triggered, but usually upon skin contact, and not usually not with the natural and synthetic latex mixes like Talay.  This is because the proteins thought to trigger these rare allergies are usually washed away in the Talay latex foam produced in the U.S.  Talay latex is a more supple version of latex.  It is more expensive and is composed of synthetic and natural latex.  Because there is no chemicals used in latex composition, it is the ILD only, that determines the feel of this product.  

Foam Vs. Air Mattress

Air mattresses have also become progressively more popular due to the interesting concept of being able to change the feel of your mattress with a control.  With many air mattresses you can change both sides of the bed to different firmnesses.  Unfortunately, an air mattress will have many parts that can and often do break.  For this reason you will find the fine print of the warranties to contain less coverage.  Also, you will not get the same contouring of the body that you can get with memory foam, as air beds will not make an imprint of your body.  In fact, it is more similar to a spring bed in that it will cause a trampoline effect and bend inward when pressure is applied without conforming to the specific bumps and curves of the body.  This is because air displaces to the sides of the body, leaving the middle with less support.  Memory and latex foam are the only substances that can accomplish a contouring of the body without losing support.