How Memory Foam Works? What’s different about memory foam? Update 05/2024

Do you feel rested today? As Benjamin Franklin observed, “There will be enough sleep in the tomb.” Perhaps you’re following in his footsteps. For most people, a good night’s sleep is the foundation of a productive day, so make that your first priority. For the rest of your life, you’ll be snoozing for about 25–30 years at a stretch. Isn’t it logical to get the most comfy bed you can afford with all that lying around doing nothing? Memory foam mattresses, which adapt to your body like a second skin, are becoming increasingly popular. This material has a distinct memory, but what is it and how does it acquire it? Let’s take a deeper look to see what’s going on!

What is Memory Foam Made Of?

As a starting point, let’s look at the physical properties of memory foam.
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You may find memory foam in many different forms, but the most common type is known as polyurethane (a large-molecule polymer). Many different materials and products can be made from the extremely common and flexible plastic polymer polyurethane, which is used in everything from furniture like sofas and beds to spray foam, elastic fibers, vehicle parts and even harsh elastomers like roller blade wheels.

In the polyurethane foam industry, “viscoelastic” is a term for “low-resistance” or “viscoelasticity” (LRPu). Polyurethane is mixed with a variety of compounds and additives to make a variety of foams.

Memory foam’s viscosity and elasticity are both affected by these substances. This means it takes a while for memory foam to change shape under pressure or transfer energy from one area to another, which is why it’s called “viscous.” By “elastic,” we mean that a material can stretch or contort without losing its original shape or size when a force is applied to stretch it;

A variety of “recipes” are used by manufacturers when it comes to the chemicals they employ in their foams and the methods they use to make the foam. Each memory foam product’s feel and performance is influenced by its unique recipe and manufacturing process, both of which are closely guarded trade secrets. Memory foam viscoelastic foams, on the other hand, typically contain some polyether polyol, a chemical that lends the foam both elasticity and viscosity.

How Does Memory Foam Work?

We’ve already discussed how memory foam mattresses are meant to gradually conform to the body in reaction to pressure, and thus evenly distribute the weight of a person. They are also engineered to be durable and to recover to their former shape when the pressure and weight of the body is removed from them.

How much “force” you put to memory foam affects its response. It takes longer for the foam to alter shape if you apply pressure immediately. It is for this reason that memory foam was originally employed in the construction of space shuttles and other high-impact environments. There are many benefits to using memory foam as a bedding material, such as distributing the weight of one’s body across a larger area and creating a slow, gradual re-configuration of the mattress to your body.

Memory foam, on average, takes about 5 to 10 seconds to return to its previous shape after a force is withdrawn. The impact’s energy is absorbed and released throughout the healing period. Sleepers benefit from the phenomenon known as “hysteresis” since it reduces some of the body’s weight (or, impact energy) on the mattress.

Memory foam’s viscosity reduces with temperature, which is a crucial aspect of how it works. In other words, when the temperature rises, it becomes less rigid and more pliable. Because your body heat raises the temperature of the sleeping surface, memory foam mattresses become softer and more malleable over time.

What’s different about memory foam?

Your bones get in the way of sleep, which is a problem. Without bones, sleeping would be easy: if you were just a big blob of muscle and fat, imagine how comfortably you’d sleep! Unfortunately, your skeleton, which houses all of that bodily tissue, is about as comfy to sit on as a bicycle’s frame.
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Open or continuous coil springs are found in traditional beds, where a mattress is supported by hundreds of coiled metal springs. There is a tendency for the whole thing to cave in when you are lying on it, but this is not entirely down to the shape of your body. If you sleep on your back, your buttocks will press further than the rest of your body, potentially causing back pain the following day. You’ll be more uncomfortable if you sleep on your side because your hips and shoulders will have to bear more of your weight. It’s common for two people to roll together in the middle of a mattress like this one, especially if you’re sharing it with someone else at night. There are at least twice as many springs in a more complex spring mattress (often 10 times more) organized in little pockets. Each spring flexes independently. With variable gauge wire, springs can be used in different regions of the mattress to provide more or less support. Because of the additional springs, mattresses with pocket springs provide much better support, but they also tend to be heavier and more expensive. The higher the “spring count,” the better the mattress.

The concept behind memory foam is remarkably straightforward. A thick layer of foam that gives way as you press down on it is an alternative to traditional spring mattresses. Technically, it’s known as viscoelastic, which means that when you apply a force it moves, but only unwillingly, and when you remove the force, it returns to its original shape. Because the foam is temperature-sensitive, it will sink in as your body temperature rises, making it more comfortable. It immediately adapts to your body’s particular shape. As a result of the foam sinking deeper into your shoulders and hips while you sleep on your side, your entire body should be well-supported and your spine should remain straight at all times. When you distribute your weight more evenly, you feel less pressure on your shoulders and hips. When it comes to alleviating back pain and arthritis symptoms, many people prefer memory foam mattresses. The mattress conforms to your changing body shape when you shift positions or flip over on it.

They might use a bit of science to entice you into buying a bed in a store. Some people claim that memory foam is preferable since it’s “viscoelastic.” There is a NASA connection to this. However, what do they actually mean by these statements? How useful are these, or are they just a scam? Find out what’s going on by going a little deeper.

What is viscoelasticity?

For example, thick lubricating oil or treacle are examples of viscous materials. The longer something takes to move from one area to another, the more viscous it is. When it comes to viscosity, honey has a high value, whereas water has a low value, hence honey moves more slowly. Elastic means that something may be stretched or deformed, but when the force is removed, it returns to its original shape and size. “Elastic” refers to items that are pliable and able to return to their original shape after being stretched. When we talk about “elastic,” we’re really referring about anything like rubber or a stretched plastic.

What does “viscoelastic” mean? If you want something that is both elastic and viscous, you want viscoelastic material (it returns to its original shape). In a nutshell, it gently deforms and returns to its original shape. Viscoelasticity is more complex than that, and this is only a simple description. Applying a constant force to a piece of memory foam with a constant area results in a long-term deformation that is known as creep in the field of materials research. Depending on how you apply the stresses, viscoelastic materials might respond in different ways. When applied quickly, they become stiffer (change shape more unwillingly) than when applied slowly, making them excellent for absorbing and cushioning shocks. You’ll also notice that a viscoelastic material will take a long time to return to its original shape after you deform it (a typical memory-foam mattress takes 5–10 seconds after getting off it to flex back to shape—much longer than a foam sponge). For cushioning, that can be highly advantageous since energy is effectively absorbed and disbursed during the time lag (a phenomenon known as hysteresis)—as is the case when a bicycle or vehicle tire squashes and flexes as it goes around. You may say that hysteresis is responsible for the “memory” in memory foam.

A viscoelastic material has the following four characteristics:

  1. Applying a steady strain causes them to slowly stretch and distort.
  2. The more you stretch or distort it, the less force you need to maintain the same degree of stretch.
  3. Force-dependent: They stretch more when you apply a force slowly as opposed to quickly.
  4. A hysteresis occurs when the material returns to its original shape after a period of stretching and relaxation.

What sorts of materials are viscoelastic?

Viscoelasticity isn’t just a fanciful scientific concept that only exists in the confines of research facilities. Materials such as leather are obvious examples of viscoelastic materials yet there are many more surprising examples like concrete and wood. Viscoelastic properties are also found in body tissue. Whether you poke a finger into your stomach, leg, or open mouth, you’ll notice that it takes some time to recover to its pre-injury state. Since human stomachs cannot be used to produce bed mattresses, synthetic materials, particularly plastics, must be used instead. To make viscoelastic foams, a mixture of polyether polyol and polyisocyanate compounds is used, with a concentration ranging from 15–75 percent (anything below 15 percent has no discernible viscoelasticity). Softcel VE-1100 from Covestro is a typical viscoelastic memory foam (formerly Bayer MaterialScience)

Why does memory foam get softer as it gets hotter?

A thick substance like treacle becomes much more watery when heated (less viscous). As a result, it should come as no surprise that memory foam’s viscosity changes with temperature. There is a decrease in viscosity as the temperature rises. To put it another way, when VE-1100 is heated to 20°C, its viscosity drops to 150cSt; when it is heated to body temperature, it drops to roughly 280cSt (centistokes). Memory foam, on the other hand, becomes a lot more squishy as it warms up, which is why you could find a memory foam mattress more comfortable after a few hours of use. When it comes to humidity, it’s just as bad.

Ordinary memory foam is unable to dissipate heat or moisture since the foam is not ventilated in any way. The fact that you’ll be sleeping on a mattress for eight hours at a time can be a major issue. Several memory foams are formed of reticulated foam, which has a more open-celled structure that improves ventilation and allows moisture to drain away from the body.
What is Memory Foam - A Look at The Pros and Cons - The Sleep Judge

Is memory foam more hygienic?

They also claim to be more sanitary because bedbugs don’t seem to enjoy living in foam. If you’re not careful, you could find bugs hiding in your bedding, rugs, walls—and in many other places—so this notion is a bit of an exaggeration. Memory foam beds may lessen the problem of bedbugs, but a strict hygiene regimen is the only effective remedy, not just a mattress change. However, certain memory foams are made with antibacterial agents and deodorants added to the polymer mix in order to enhance cleanliness.

Viscoelasticity in everyday life

Memory foam isn’t just for mattresses and pillows; it can be used in a variety of other products as well. My new noise-isolating headphones came with a whole set of earplugs, some of which were constructed from memory foam. Squeeze them into your ear canals until they form a tight seal, and then let go to let out any undesirable background noise.

For the best quality foam earplugs (also known as “ear defenders”), you should keep in mind that they’re manufactured of memory foam. With your finger placed on the end for around 30 to 60 seconds, you’ll notice that they gradually expand to fill your ear canals and seal much better than if you immediately withdraw your finger after pushing them in. Why? Viscoelastic materials have a temporal lag between deformation and relaxation, and we need to exploit this to our advantage.

The term “viscoelasticity” is frequently heard in the medical community. Aside from the obvious pressure-relieving cushions and hydrocolloidal wound-care dressings, you’ll find memory foam in many other products as well (used in blister plasters). You need to know about viscoelasticity whether you’re an eye surgeon, a prosthetist, or if you’re constructing artificial skin that behaves as nearly as possible to the genuine thing—to name just three instances.

When NASA launched the Challenger Space Shuttle for the final time on January 28, 1986, it was a momentous occasion for viscoelasticity to make history. To ensure a tight fit and a strong seal, rubbery materials such as seals and gaskets are often viscoelastic. They may be able to seal better or worse depending on the temperature at which they are being used. Those O-ring seals couldn’t bend and seal properly because of the extreme cold on that day in February. The fuel tanks erupted, igniting hot, high-pressure gases, destroying the Challenger and killing all seven people on board.

How to Pick The Right Memory Foam Mattress?

If you’ve concluded that memory foam sounds like the appropriate decision for you, there’s still a good deal you need know when hunting for the ideal memory foam mattress match. What to look for in a memory foam mattress can be summarized as follows:


Mattresses come in a variety of firmness levels. Many mattresses are described in terms of their firmness, which can be broken down numerically from 1 (extremely soft) up to 10 (very firm) (very firm). Think of it as a more complex version of the story of Goldilocks and the Three Bears: some people prefer their beds to be quite hard, while others prefer them to be extremely soft.

Most mattresses will be described in-store or online as falling somewhere on the soft-firm spectrum. However, if that info isn’t there or if it isn’t detailed enough, you can search for an Indentation Load Deflection (ILD) grade. This is basically a measure of firmness: the greater the ILD rating, the firmer you can expect the mattress to be. According to the way ILDs are evaluated, each layer of the mattress (ie, comfort, transition, support, etc.) has its own ILD score, and then the mattress as a whole has an overall ILD score. On the ILD scale, a mattress with an overall ILD of 10 would be very soft, while a mattress with an ILD of 50 would be quite hard. If you want anything in the middle, evaluate by those standards.


It is the amount of actual foam in each layer of the mattress that determines the density of memory foam. Different densities of memory foam are measured in pounds per cubic foot (lb/cu ft) (PCF). In general, the higher the density of the foam, the longer it will hold its shape, elasticity, and support structures. However, larger density foams also tend to sleep hotter.

Assuming you sleep at a normal temperature, a PFC density of 3.0-5.0 is a fair compromise between longevity and heat retention for average-temperature sleepers.


The thickness of a memory foam mattress is measured from the side of the mattress. For example, a three-inch thick piece of foam could have an ILD rating of 10 or 50, depending on its density. The thickness of memory foam mattresses ranges from 6 to 14 inches. Thicker mattresses are often more supportive than thinner mattresses, however this isn’t always the case.

In addition to the overall thickness of the mattress, the thickness of each layer should be taken into account. Comfort and transition foams should be at least four inches thick between the sleep surface of the mattress and its foundation. As a result, the mattress will not become too uncomfortable for you to enjoy the benefits of the mattress’s support core.

Certifications based on standardized testing

Additives in cheaper memory foam mattresses can damage the substance, reduce its lifespan, and even cause irritation and/or emit fumes that are questionable in terms of health. Look for the Certipur-US seal of approval while shopping for a mattress. In order to confirm that the memory foam in the mattress is safe for both your health and the mattress itself, this stamp of approval has been issued.

Mercury, lead, heavy metals, or formaldehyde are not permitted in the production of a Certipur-US certified mattress. Additionally, they are free of phthalates (plasticizers that may impair reproductive health) and PBDEs (polybrominated diphenyl ethers) (Polybrominated diphenyl ethers, a flame retardant that is banned in the US for negative health effects, but which is sometimes used in mattress manufacturing abroad). They also have lower levels of volatile organic compounds (VOCs), which are the primary cause of the off-gassing chemical smells.

The peace of mind that comes with purchasing a mattress with certified foam is well worth the extra time and effort spent determining whether or not a mattress is certified before making a purchase.
What is Memory Foam - A Look at The Pros and Cons - The Sleep Judge

What’s So Special About Memory Foam?

Memory foam’s unique ability to mold to your body’s contours is what makes it so fantastic. Conventional mattresses frequently fail to provide adequate general support for the body as well as adequate relief for the numerous pressure points on which we sleep.

Hard points on the skeleton, such the elbows and hips, make lying on them uncomfortable after a while – bodily sections like the back can also be affected by a lack of proper support. Memory foam provides supple support and wraps around you for superior, more personalised support by cushioning your entire body.

Memory foam mattresses respond to a more subtle shift in pressure than spring mattresses, which rely on a vast weighted area to affect its cushioning structure. As a result of the viscoelastic substance utilized, the memory foam design is influenced by its ability to return to its previous shape once a large amount of pressure is applied. In addition to being a temperature sensitive material, the foam is ideal for use with the human body.

Why Is Memory Foam Good For You?

To begin with, a good traditional mattress may have a few hundred springs beneath you, but memory foam is like sleeping on a million tiny springs that work together to support your body.

The fluid-like responsiveness of a memory mattress provides for a better night’s sleep than a regular mattress, which might worsen pressure point difficulties.

A third benefit of memory foam is that it feels like it has been sculpted to fit your body.

Do you have trouble falling asleep? Moving around on a memory foam mattress does not disturb your sleeping partner, as is the case with spring mattresses.

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