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Foam Densities Explained | Sloom

Foam Densities Explained

Mar 21, 2019 | By Rudo

There are a few terms in the bedding industry as ambiguous as foam density. It is a term marketed widely on the majority of beds. Even Spring coil mattresses consist of high-density foam. However, what does it mean, and what effect does foam density have on a foam mattress?

Foam Mattress Density is a measurement that compares the amount of matter the foam has to its volume, usually expressed in kilogram per cubic meter (kg/m3). In simple terms, if you weigh a 1m x 1m x 1m block of foam, the weight of that block will indicate its density.

The higher the density, the more raw material is used to produce the same size of foam compared to a less dense foam, hence the increased price. A higher density foam mattress means higher quality and durability and should not be confused with firmness. One can have a very high-density rating in foam, and it can be as soft as a very low-density foam.

Another aspect that adds to the confusion of foam density is that some manufacturers add fillers to the foam. These fillers artificially increase the density of the foam without the quality and durability that goes with such an increase. It is therefore essential to note that Sloom uses pure foams without any fillers on our foam mattresses.

Densities of different foam types

There are many kinds of foam, and since they are all produced using different processes and with varying raw material, there are aspects relating to density that you should be aware when comparing different foam mattresses densities.


Polyfoam or Polyurethane foam is by far the most common type of foam, and the least expensive of all the foams to produce. The most common misconception about this type of foam is that it quickly sinks in or sags. Low and medium density polyfoams do sag and indent easily as it can’t support the heavier weights. Higher-density foam mattresses will then be able to support more weight.

Polyfoams with a density more than 23kg/m3 are considered high density. Majority of high-density foams used are in the range between 23kg/m3 to 28kg/m3 depending on whether it is a turn foam mattress or a do not turn foam mattress.

It is important to note that if you are a heavy person, you want to look at high-density foam of more than 28kg/m3 for a core foam. The higher the density, the better it will support you for longer.

The Sloom Original Mattress uses a Pure 35 density foam as the core for better support and durability.

Rebond Foam

Rebond Foam is made from recycled shredded waste foam; usually, polyfoam, reprocessed into one solid foam block and then cut into the desired size. The density of rebond foam is a lot higher than virgin polyfoam but the price per kilogram it far cheaper.

Rebond foam is widely used as a core in foam mattresses and is usually very firm. Densities used can vary between 40kg/m3 to 100kg/m3. Due to it being such a firm foam, it can make the overall foam mattress a bit too firm for someone that isn’t very heavy, even with additional comfort layers. Rebond is not a premium foam.

Sloom don’t use any rebounded foams in our products.

Latex Foam

Latex foam can either refer to natural latex or synthetic latex. The former is made from the rubber tree which doesn’t grow in South Africa, resulting in a hefty price tag for natural latex to be imported.

Synthetic latex, on the other hand, is an excellent premium foam with similar elastic properties as natural latex but with a far better value for the money price tag.

HR Foam

HR Foam or High Resilience foam is technically also a polyurethane foam, but with a few differences due to chemical makeup. It is a premium foam with excellent elasticity, and optimal supporting force, this type of foam distributes pressure across an entire surface as to help absorb motion.

This foam is also very breathable, allowing for a cooler sleeping surface and less heat buildup. To qualify as an HR Foam, the density rating should be at least 40kg/m3 or more.

Sloom uses a 55 Density HR Foam designed and formulated to incorporate properties of latex foam in an all-round durable and breathable foam.

Memory Foam

Memory Foam or Viscoelastic foam mattresses contour to the pressure, returning to its original shape slowly. It has  excellent pressure point relieving properties without compromising support. Due to its construction, memory foam is much denser compared to polyfoam, and densities range between 30 kg/m3 to 100kg/m3 for mattress purposes.

Quality memory foam should have at least a 50 Kg/m3 density as anything less is not durable. We use a 55kg/m3 density quality memory foam in our Original mattress.

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