A Comprehensive Guide to Foam Mattresses
One of the most important parts of a mattress is the most difficult to see. It’s not the size or the brand. It’s the guts of the mattress. Just like every mother says, it’s what’s inside that counts, and when you’re talking about the insides of most mattresses, you’re frequently talking about foam.
You’ve likely heard of memory foam as an alternative to traditional foam mattresses, but just what is that non-memory foam? And are there other alternative foams that could fit your needs even better?
Consider your questions about foam mattresses answered. We’ll run down for you the different types of foam, the materials they’re made of, the pros and cons of each type, and ways to compare mattresses within and across types, so you can find the foam mattress that’s perfect for you.
Polyfoam, known as polyurethane foam and flexible polyurethane foam, is the most common type of foam in mattresses. You may recognize it as the foam used in couch cushions and many egg crate mattress toppers.
Mattress makers began to use polyfoam as an alternative to natural fibers like cotton and wool in the late 1950s. They used it as both an upholstering layer in innerspring mattresses and as a core for fully foam mattresses.
Polyfoam presented many benefits over natural fibers.
Manufacturers could make it at different grades of firmness, which allowed them to provide a wider variety of mattresses to their customers. It is also flame-resistant and inexpensive to make. Polyfoam conforms to an individual’s body shape when they lie on it and returns to its original shape much quicker and more fully than natural fibers.
Polyfoam is derived from petroleum. Polyfoam makers combine two chemicals to make the foam: polyol, which is a complex alcohol, and one of a family of chemicals called isocyanates. The most common isocyanates used in the creation of polyurethane are toluene diisocyanate, or TDI, and methylene diphenyl diisocyanate, or MDI.
This is where some controversy about polyfoams comes into play. Isocyanates are highly reactive chemicals, and in their unreacted states, they can irritate eyes and gastrointestinal and respiratory tracts. They can also cause inflammation through direct contact with skin.
When isocyanates are fully reacted and cured, they are widely considered non-toxic. The controversy comes in the disputes to this claim.
Benefits and Drawbacks of Polyfoam
While we’ve hinted at some of the pros and cons of polyfoam mattresses so far, let’s dig deeper into the benefits and drawbacks of this type of foam.
- Polyfoam is inexpensive. Since polyfoam is the least expensive type of foam for manufacturers to make, mattress companies can pass those savings on to consumers. The relatively low price of a polyfoam mattress makes it a solid choice for a student or young adult purchasing their first mattress on their own.
- It’s widely available. Another benefit of the ease of manufacturing polyfoam mattresses is that they are easy to find in stores and online.
- It sleeps cooler than other types of foam. The open cell structure of polyfoam—a cross-section has the appearance of interlocking cells with open windows surrounded by struts for support—allows these mattresses to breathe and gives them the ability to conduct body heat away from the sleeper, resulting in a cooler night’s sleep. A common complaint with other types of foam mattresses is that they sleep hot, and polyfoam reduces this effect.
- It’s resilient. Its open cell structure also means polyfoam bounces back to its original form quicker than other types of foam. This comes in handy for heavyweight sleepers and people looking for a mattress that is good for sex.
- Mattresses can deteriorate quickly. Many companies manufacture subpar polyfoam mattresses that do not hold their shape for very long. They overcompensate for low-quality foam by making these mattresses thicker, but this does not prevent lower quality polyfoam mattresses from developing body impressions and losing their qualities of comfort and pressure relief.
- Support can be incomplete. A polyfoam mattress does not conform to the body the way other foam mattresses do, and some people need more than the generalized support that a polyfoam mattress provides. Polyfoam is also known to offer below-average edge support.
- It allows some motion transfer. Polyfoam offers some motion isolation, but other types of foam are more effective in this department.
The primary point of comparison between polyfoams is density. Density is measured in pounds per cubic foot, or PCF. Foams with lower PCFs are less dense than those with higher PCFs. Denser polyfoams are more durable than less dense polyfoams.
Firmness is measured as Indentation Load Deflection, or ILD (sometimes referred to as IFD for Indentation Force Deflection). Density does not necessarily correspond to firmness, though there is some correlation.
Technically, ILD numbers equate to the pounds of pressure required to indent a four-inch piece of foam by 25%, but simply put, they are reflections of how soft or firm a mattress is. The lower the ILD, the softer the mattress, and the higher it is, the firmer.
Since polyfoams are often used as support rather than surface layers in mattresses and ILD closely corresponds to surface feel, density is the most common measure of quality for polyfoam mattresses.
- Conventional polyfoam is the lowest grade. It is often used as a soft comfort layer in mattresses that include other types of foam. Its density is less than 1.5 PCF, but polyfoam with a PCF less than 1.2 is not suitable for even the least frequently used mattresses in a home.
- High Density, or HD, polyfoam is the next grade up from conventional polyfoam. It rates from 1.5 to 2.5 PCF, but experts do not recommend HD polyfoam that is below 1.8 PCF. HD polyfoam lasts longer than conventional polyfoam, and it can provide effective support in thin layers.
- High Resiliency, or HR, polyfoam is the highest quality polyfoam. To qualify as HR, a foam must have a support factor of 2.4 PCF or higher. HR polyfoam has a different chemical makeup and cell structure than the lower quality polyfoams.
Because of this different formulation, manufacturers can make it in a variety of ILDs. Thus, this high-density polyfoam can feel either soft or firm depending on how it is produced. HR polyfoam can demonstrate high resilience and last for years.
True to its name, memory foam is the type of foam that conjures the most memorable images in people’s minds. Perhaps you think of a glass of wine that stands still while someone jumps up and down next to it on a mattress. Or you may think of a hand pulling away from a memory foam mattress and leaving an indented print that slowly disappears.
Memory foam is known for this ability to conform to and “remember” the shape of the object or body on top of it.
Memory foam’s origins date back to 1966, when NASA contracted engineer Charles Yost to help improve the crash and vibration protection of airline seating. Yost developed “temper foam,” which possessed shock-absorbent qualities and a soft feel. Sports and medical equipment began to use memory foam in the 1980s, and Tempur-Pedic unveiled the first memory foam mattress in the early 1990s.
Memory foam is manufactured similarly to polyurethane, but it incorporates additional elements such as gasses or blowing agents that make it more viscous and denser than polyfoam. Another name for memory foam is viscoelastic foam because it demonstrates elasticity by returning to its original shape and viscosity by resisting flow. This is how we get the slowly disappearing handprint.
One of the most common complaints with memory foam mattresses is that they retain heat, but three types of memory foam employ different methods to counteract that phenomenon and help memory foam mattress owners sleep cooler.
- Open cell memory foam has a similar composition to polyfoam. Its many tiny cells allow air to flow through it, which keeps a mattress cooler than heat-trapping closed cell memory foam. Plant-based memory foam often features open cell structure, and since plant-based mattresses are more natural than purely synthetic memory foam mattresses, they include fewer of the volatile organic compounds (VOCs) that result in the unpleasant off-gassing that is another common complaint with memory foam.
- Gel memory foam mattresses combat heat-retention complaints by using gel to regulate a sleeper’s temperature. The gel is either infused into the foam or forms a separate layer on top of the foam. Fans of gel memory foam claim that the gel helps regulate body heat, which means it can not only absorb heat to keep you cool but also store and release the heat it absorbs to warm you when your body naturally cools during sleep.
- Copper-infused memory foam is one of the newest innovations designed to improve on traditional memory foam. Manufacturers of copper-infused memory foam mattresses boast copper’s cooling, hypoallergenic, and anti-inflammatory qualities. There may be substance to these claims, but since they often come directly from manufacturers rather than third-party organizations, it is wise to consider them carefully. The benefits of copper-infused compression clothing are difficult to validate, and the same goes for copper-infused memory foam.
Benefits and Drawbacks of Memory Foam
People tend either to love or to hate memory foam. Here are the arguments in favor of both sides.
- Memory foam offers targeted support and pressure relief. Its cradling effect promotes proper spinal alignment and circulation, which makes it ideal for side sleepers and people with back and neck problems.
- It’s comfortable. Memory foam conforms to the body more than any other type of foam. The softness and support of a high-quality memory foam mattress is a winning combination.
- It isolates motion. Because of memory’s foams deep cushion, motion on one part of a memory foam mattress is isolated from spreading to other parts of the mattress. If one member of a couple tosses and turns more frequently than the other, a memory foam mattress can keep that movement from affecting the other partner.
- It sleeps hot. Manufacturers are innovating to combat the heat-retaining properties of memory foam, but a hot sleep remains one of the biggest drawbacks of this type of foam.
- There is an initial odor. When a memory foam mattress is unwrapped, the VOCs it releases come with a strong chemical odor. This odor is harmless and disappears over the course of a few days or sometimes hours, but it is still enough to deter some consumers.
- There is very little bounce. This is the flip side of motion isolation. Because of their sink, memory foam mattresses are not the most conducive to sex or people who shift a fair amount in their sleep.
Comparing Memory Foams
Memory foam is denser than polyfoam, so its range of densities exists on a different part of the scale. The lowest quality memory foams are 3.0 PCF and below, while the highest quality memory foams reach up to 7.0 PCF. The benefits of lower density memory foams include less heat retention and off-gassing, but as with polyfoam, the denser memory foams generally last longer.
ILD is used more frequently with memory foam than with polyfoam. Memory foam ILDs range from under 10 to above 16. Memory foams with ILDs of 10 and under are very soft with lots of sink whereas a memory foam with an ILD of 16 is among the firmest of this type.
The Mayans and Aztecs used latex to make rubber balls as far back as the sixth century, but the process for turning this rubber tree sap into foam did not exist until the early 20th century. The first latex foam mattress followed in the early 1930s. Latex foam mattresses have exploded in popularity recently thanks to their durability and environmentally friendliness.
Latex foam appeals to consumers looking for a “green” mattress because the source of natural latex is the rubber tree. But not all latex foam is equally eco-friendly. Some natural latex is organic, as certified by the Global Organic Latex Standard (GOLS), but other natural latex involves non-organic chemicals in the growing or processing of the sap. There are also synthetic methods of creating latex, and many latex foam mattresses feature blends of natural and synthetic latexes.
There are two basic processes for turning rubber sap into latex foam. Dunlop is the older process, dating back to 1929, and it creates a firmer latex foam. The other process, Talalay, was pioneered in the 1950s and produces a softer latex often used as a top cushion layer. Some companies use “Dunlop” and “Talalay” as interchangeable synonyms for “natural” and “synthetic,” but manufacturers may use either process to make natural or synthetic latex foam.
Benefits and Drawbacks of Latex Foam
Here are some of the reasons latex foam has become so trendy and some of its downsides.
- Latex foam is often eco-friendly. Synthetic versions aside, latex foam gives consumers a natural, minimally processed alternative to polyfoam and memory foam.
- It’s versatile. Since latex foam is available in a wider range of firmness than other types of foam, it can accommodate a wider variety of body types and sleep positions.
- It’s the most durable. A high-quality latex foam mattress can last decades with the proper care.
- It isolates motion. Latex foam also boasts the motion isolation qualities of memory foam.
- It can be expensive. You get what you pay for, and with higher quality and durability comes a higher price.
- Some mattresses sleep hot. This is a greater issue with closed cell latex foams than with open cell latex foams.
- It runs firm. Some latex foam mattresses are firmer in their first few weeks of use and need to be broken in.
Comparing Latex Foams
Firmness, not density, is the standard of measurement for latex foam. The softest latex foam mattress is around 14 ILD, and the firmest hovers close to 44.
Another attribute that comes in handy when judging latex foam mattresses is known as support factor, or compression modulus. Firmness reflects the pressure it takes to indent a foam by 25%, but support factor compares that ILD number to the pressure it takes to indent a foam by 65%. A foam’s support factor shows how well it ultimately supports a load placed on it rather than just its surface feel.
Latex foam mattresses frequently sport high support factors, which means even softer latex foams can provide decent support.
Not all foams are created equal, and neither is one the clear standard bearer for quality over the others. Just like with most other aspects of a mattress, the way to find the mattress foam that works best for you involves knowing a few things ahead of time:
- Your sleep style.
- Your budget.
- Your preferences when it comes to temperature, firmness, and motion.
- Your priorities.
Many mattress companies hold the exact composition of their mattresses as trade secrets, and complete transparency is rare. Also rare are the mattresses comprised of only one type of foam. Most are hybrids with layers of various types.
These complications make it difficult to turn your new foam knowledge directly into mattress purchasing decisions, but it may inform your questions for a mattress retailer. And it never hurts to ask.