Why Memory Foam Density Is Important

When you're shopping for a memory foam mattress it's no different than shopping for a coil spring mattress. There are certain criteria that you're looking for in order to ensure you get a quality, comfortable mattress that will last a significant amount of time. Near the top of the list is memory foam density, because density is about much more than just personal comfort. Density ratings tell a lot about a mattress - including its quality and durability.

How Memory Foam Density Is Calculated

Fortunately, memory foam density is measured in a very specific way in order to achieve some level of standardization. The process involves cutting a 12-inch cube from a foam lot and then weighing it on a certified scale. If it weighs 4 pounds then it's designated as having a 4lb. density. A weight of 5 pounds equals a 5lb. density, and so on. It's a pretty simple formula which ensures standard measurements regardless of where the foam is produced.

Despite the simple measuring system it's important to note that memory foam density ratings can be a little bit deceiving. That's because from a chemistry standpoint, weight and density are two different things. Weight is a measurement of the gravitational pull on an object while density measures how closely packed the molecules of a substance are. So while they are similar in some aspects, they are different enough to cause a smart consumer to beware.

Fraudulent Memory Foam Densities

Understanding the difference between weight and density as scientific measurements explains why some memory foam manufacturers can sell a product of the same density rating at a lower cost than their competitors. This is especially true in countries where government regulation of memory foam manufacturing is very loose. Unscrupulous manufacturers have figured out that they can add clay or some other heavy filler into memory foam, thus achieving the same weight without having the proper density.

Such practices result in a lower quality foam that breaks down more quickly, tends to not be as firm and supportive, and more or less defeats the purpose of using a memory foam mattress or topper. When you're buying a memory foam mattress you need to be sure that it was manufactured in the United States (if that's where you live), where government regulation is extremely tight. While it's still possible to get fraudulent densities with American-made foam, it's a lot less likely.

Density and the Support

With fraudulent density ratings out of the way, it goes without saying that memory foam density is important in terms of the firmness of a mattress. When buying a topper you can easily get away with a density of 2.5 or lower. But you should consider it least a rating of 4 or better if you're getting a full mattress. Even if a lower-rated density seems comfortable enough for you, it will break down much more quickly than a higher density mattress. If it's a matter of a higher-rated mattress being downright uncomfortable, then obviously you have to weigh the importance of durability against less-than-perfect comfort for the first year or two.

Another aspect regarding the firmness of a memory foam mattress has to do with the foundation you lay it on. Many people make the mistake of lying a memory foam mattress on top of a traditional box spring; but doing so defeats the purpose of having memory foam. The box spring interferes with the normal operation of the memory foam and can make a mattress with a density rating of 5 feel like one that's been rated a 2. Regardless of your memory foam density, the mattress should always be laid on a flat, firm foundation.

Density and Temperature

The last concern when it comes to memory foam density is in the sleeping temperature; known in the industry as how "hot" the bed sleeps. In simple terms, memory foam by its very nature doesn't offer the same breathability as a quilted top innerspring mattress. Unfortunately, there's really nothing you can do about it.

That said, the lower the density of the foam the more hot it will sleep. That's because a lower density will result in more of the skin surface coming in contact with the mattress. Higher density foam will involve less skin contact. Think of it in terms of water, in both its liquid and frozen states.

Fortunately, there are measures you can take to mitigate an uncomfortable sleeping temperature, including a quilted topper and specially designed sheets. These two methods are especially effective if you're willing to invest the money in good, quality products. The best ones on the market can reduce sleep temperature significantly to the extent that some people can't tell the difference between a memory foam mattress and their old innerspring.