ABCs of Memory Foam

Memory foam is a unique and interesting material, from its origins at NASA to the unparalleled pressure relief it provides in bedrooms around the world. Find out the top facts and features of this mattress type in our A to Z memory foam glossary.

Ames Research Center

Memory foam came into being as scientists at the Ames Research center, a NASA contractor, researched ways to protect astronauts from harmful G-Forces during take-off and landings. Although memory foam never made its way into space shuttles, the practical uses in seating and bedding applications here on earth became apparent and NASA released it to the public domain.

Memory foam was created by scientists at NASA's Ames Research Center

Body Weight

One of the key benefits of memory foam is its ability to spread the weight of the user across the surface of the material due to an open-celled structure. This prevents pressure points and helps support the natural alignment of a person’s body since bodyweight is not concentrated on certain points as with other materials like springs.

Memory foam has the ability to spread your body weight evenly across the surface of the mattress

Density

Density is a measure of mass, and with memory foam, this refers to the weight of one cubic foot of material. Memory foam density can range from low (3.5 lbs and under), to medium (3.5-5.0 lbs) to high (5.0 lbs and up). Higher density foams better resist softening and compression over time compared to low density, but are more expensive and may also be more prone to heat, odor, and the "quicksand" sensation. Low density foams have a short lifespan and may lack support, but tend to be cheaper (though not always).

Memory foam density is the measure of mass divided by volume of 1 cubic foot of memory foam

Eco-friendliness

This concept refers to a product that has a reduced or minimal impact on the environment. While the term is fairly ambiguous, eco-friendly memory foam may refer to one that uses less chemicals or petroleum than conventional memory foam, is shipped in a way that conserves resources, and/or foam that is manufactured in a way that reduces or eliminates emissions.

Amerisleep mattresses are eco-friendly and have a minimal impact on the environment

Firmness

Memory foam mattresses can be made in a wide range of firmnesses from extra soft to extra firm. The firmness of a mattress will depend on several factors, from the ILD of the foam to the thickness of the individual layers. Memory foams that are temperature sensitive can have variable firmnesses depending on the room’s temperature, and usually soften with body heat as well.

Memory foam mattresses can be made extra soft all the way to extra firm

Gel

Memory foam mattresses with gel are a newer trend, and brands with gel claim it helps keep sleepers cool. The gel can be infused via particles, mixed in as a liquid during manufacturing, or may be included as a separate gel pad layer. Gel can initially feel cool at room temperature, though eventually will take on the sleeper’s temperature. Compared to conventional memory foam, gel mattresses do have slightly less heat complaints, though plant-based foams have still been shown to be the most breathable.

Brands with gel memory foam claim it keeps sleepers cool, but can actually make them sleep hotter

Heat

Sleeping hot is a concern for many people, and traditional memory foams often get associated with trapped heat. Less dense foams, those with larger cells, and those with less temperature-sensitivity tend to sleep cooler. In general, about 10-15% of people report heat on conventional memory foam (compared to about 2-3% on Amerisleep mattresses).

Less dense foams and foams with larger cells will generally sleep cooler

IFD/ ILD

Indentation Force Deflection or Indentation Load Deflection provide a standardized way to measure firmness with foams, expressed as the pounds of force necessary to compress the foam sample by 25%. According to the Polyurethane Foam Association guide, ILDs for mattresses typically fall between 24 and 45. For memory foam specifically, the average ILDs tend to range between 10 to 16. However, the density and thickness of the foam will also influence how firm or soft it feels. Amerisleep’s beds have core ILDs between 28-35, and comfort layer ILDs of 12, with varying thicknesses of memory foam yielding different firmnesses.

ILD/ IFD firmness chart

Joints

Memory foam helps support a person’s natural skeletal alignment and does not place added pressure on sensitive areas like hips, knees, and elbows. This prevents joints from straining, falling asleep, or getting stiff overnight, and generally reduces daily aches and pains compared to other mattress types like innersprings and water.

Proper support for your spine

Kids

Memory foam mattresses can be safely used by children old enough to reposition themselves over (5 years and older, generally). However, most experts recommend firm mattresses for kids through pre-teen age, so choosing a firm, less viscous model and avoiding harmful chemicals would be top considerations.

Things to consider when buying a memory foam mattress

Layers

Memory foam mattresses all have a similar construction, which includes a core foam layer of 4-9 inches that supports the memory foam layer of 1 inch or more. Some brands may use multiple layers of memory foam, or include other foams or materials in the upper layers. Brands with innerspring or latex cores would be considered hybrid mattresses and not “memory foam mattresses.”

Memory foam mattresses are made up of layers to provide comfort and support

Memory

The “memory” aspect of memory foam refers to the temporary impression made after pressure is applied. After you press your hand into memory foam, for example, it will take anywhere from 8-45 seconds or so to come back to its original shape since the material adjusts to absorb the pressure rather than resisting it. This is in contrast to materials like latex foam, which spring back instantly.

Pressing hand into memory foam

Natural

The term natural or plant-based in relation to memory foam means a portion of the petroleum-based polyols have been replaced with plant-based polyols. Note that brands using 100% natural latex would be considered latex mattresses and not memory foam (since the chemical structure, manufacturing and end product are not the same).

Amerisleep uses natural plant-based polyols in the construction of their mattresses

Off-gasssing

This refers to the “chemical’ odor that nearly all newly manufactured products release. Off gassing is a result of volatile organic compounds (VOCs) which break down and release odors into the air. Examples include new car smell, new furniture smell, fresh paint smell, etc. Traditional memory foam can contain various VOCs and about 15% of people complain of significant odor in the first weeks of ownership. With Amerisleep’s mattresses, which meet low-VOC guidelines, less than 3% of people complain of odor.

Tempur-Pedic® off gassing

Polyurethane

Polyurethanes encompass a broad range of products, from foams to wheels to gaskets to Spandex and more. Polyurethane foam is made by reacting isocyanates with polyols and a few other ingredients, creating a gas reaction. All memory foam is a form of polyurethane, although with a slightly different components that changes the viscosity and density to yield the “memory” characteristics. Mattress cores are typically regular polyurethane.

Chemical formula for polyurethane

Quicksand

In some reviews of memory foam mattresses, people may complain of feeling like they are stuck in quicksand or find it difficult to change position or get out of bed. This is most common with high-density memory foams that are more viscous, slow-response, and temperature sensitive. These traits work together to create foam that is soft near the sleeper but firmer around the sleeper and slow to respond to the person’s movements, requiring greater effort to move about.

Tempur-Pedic® sinking in mattress

Relief

Relief of pain and pressure points are two key benefits of memory foam. Other materials like springs exert pressure upwards, against the sleeper’s body that is being pushed down by gravity. This can create painful pressure points on areas like hips, shoulder, and elbows. Memory foam’s ability to adjust to a person’s shape without exerting upward pressure supports proper alignment and significantly reduces pressure points.

Pain and mattress types

Satisfaction

Overall, memory foam mattresses are the highest rated mattress type in terms of consumer satisfaction and ratings. Four in five people are happy with their memory foam mattress, compared to three in five spring mattress owners. Amerisleep mattresses have one of the highest owner satisfaction ratings for memory foam, with review scores of 4.5/ 5 stars and higher, and nearly 95% or more of our customers saying they would recommend our mattresses to a friend.

Amerisleep mattresses have the one of the highest owner satisfaction ratings for memory foam

Temperature-sensitivity

Temperature sensitive foams change their characteristics depending on ambient temperature. These memory foams are firmer when cooler, and softer when warmer. The material is designed to soften with the sleeper’s body heat in order to contour more closely. This is primarily found with traditional and high density foams, and while some like the sinking sensation, others may find it uncomfortable or equate the sensation to quicksand.

Temperature senstive foams are firmer when it's cooler, and softer when it's warmer

Unmoving

On some types of beds, one person’s movements can disrupt their partner due to motion transfer. One of the key benefits of memory foam is that it excels at preventing motion transfer, meaning your partner’s moving or getting out of bed will not disturb you on the other side of the bed.

Customers with memory foam report no motion transfer between partners

Visco-elastic

In relation to memory foam, viscosity refers to how the material reacts to pressure. More viscous foam creates a gradual sinking sensation when you lie down, and will be slower to react to changes in position or pressure, whereas less viscous foam contours more rapidly. Memory foams that show higher temperature-sensitivity and density will be more viscous at cooler temperatures. Elasticity refers to a material’s ability to spring back. Memory foam has enough elasticity to return to its original shape, but is not as resilient as latex or springs, for example.

Spring and dash plot used for measuring visco-elastic material

Warranties

Warranties and guarantees for memory foam differ from those of spring beds. Usually, memory foam offers longer warranties, and quality brands will offer at least 10 years of full coverage which cover the average or expected lifespan of the bed. With memory foam, impressions or sagging represent the primary concern, and quality brands will cover sagging at 1-inch or less. This is important since impressions over 1-inch can lead to increased decreased comfort.

How to measure a sagging memory foam mattress

X

Of the 120 or so words beginning with X, none really apply to memory foam. However some memory foam might appear to be xanthic over time (yellow in color), and mattress foundations should be solid, or xyloid (having qualities of wood)!

Some memory foam might start to yellow over time

Years

Memory foam mattresses are one of the longest-lasting mattress types, and with medium and high density foams you can expect to get 8-10 years or more out of the average bed (versus 5-6 years with low density foams and spring beds). Factors that might negatively affect longevity include low foam density in the memory or core layers, poor quality manufacturing, and inclusion of padding or regular foams. Frequency of use, user size, and care (rotating, preventing stains and spills) can also play a role in mattress lifespan.

Lifespan of different mattress types

Zero-emissions

Some types of memory and poly foams are made in a way that can contribute significantly to air pollution, especially when harmful blowing agents and other polluting chemicals are used. Memory foam like Amerisleep’s Bio-Pur™ that is produced with zero-emissions is manufactured without these harmful components and in an enclosed chamber that filter any potential pollution, making the process more environmentally friendly.

Amerisleep's Bio-Pur™ memory foam is produced with zero-emissions

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