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A guide to memory foam

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What should I look for when buying a memory foam mattress?

There are many factors that can influence what kind of mattress you buy, from the basic practicalities of bedroom size, bed base size, and budget, to the memory foam specific ones like how do you measure how firm the mattress is?

Let's cover the basics first. It is good advice to buy as big a mattress as you can afford or as space will allow. You will spend a large percentage of your life lying on your mattress - you should try and make sure it is as comfortable and spacious as possible.
For memory foam mattresses, there are several figures that can help give you a basic impression of the overall quality and comfort levels, but these are still only a guideline. You must also consider the dimensions of the memory foam mattress, and the composition of its layers and its overall construction.

The main thing to concern yourself with is the depth of the mattress and what percentage of that is a memory foam layer. Our mattresses for instance are 21cm thick overall, with 9cm of memory foam. We find that that is the optimum amount of memory foam to offer complete support. Some 8" mattresses will have only 2" of memory foam or sometimes less, which we find isn't really enough. This is the same reason we don't stock mattress toppers, we find that whilst they give a good impression of memory foam, they are too thin to offer the genuine support that should come from a good memory foam mattress.
Next, you will want to know about the various technical measurements you can measure your memory foam mattress by.

What does the density of a memory foam mattress mean?

There are several different measurements you can use to judge or compare memory foam mattresses. The main two are the density, and the ILD rating.


One of the main measurements to refer to is the density of the memory foam. It is often expressed as a weight, ie; 4lb or 65kg/m3. This should really be expressed as a density though, i.e. - it really means 4 pounds per square foot, or that a cube of the foam 1 foot in each direction would weigh 4lbs. Whilst this measurement doesn't give you the whole story, you can use it as a good rule of thumb.

To get a denser memory foam, the manufacturer has to put in more of the raw materials that compose the foam. The most expensive mattresses you can buy use a 5 or a 5.5lb memory foam, and the cheapest end of the scale have started to use as low as a 2.5lb memory foam. The difference in quality is very noticeable. The lower end of the scale does not offer the same lush, soft genuine memory foam feeling you get from a decent density of foam.

Our memory foam mattresses all use a 5.3lb (85kg/m3) memory foam, which we feel offers you the comfort levels of a £1000+ mattress at a reasonable price. But obviously we have a vested interest in this - have a look for yourself and compare the prices and densities of our competitor’s mattresses and ours - we're convinced you'll feel the same way we do.

What does the ILD rating of a memory foam mattress mean?

The second main figure you should be looking for when buying a memory foam mattress is its ILD rating.

ILD stands for Indentation Load Deflection. In simple terms it is a measurement of how hard or soft a foam is. In more accurate terms it's the number of pounds of pressure required to indent 4" of foam by 25% using a 50 square inch indentation. You may also see it referred to as the 25% ILD rating.

For example, this means that a 15lb ILD rating would mean that the foam needed 15lbs of pressure to indent it by 25%, and a 25lb ILD rating would mean it needs 25lbs to indent by 25%, so basically this means that the higher the ILD, the firmer the foam.

You can use the ILD rating together with the foam's density to gain a good idea of the overall make up and quality of the foam.

It is worth noting that due to the batch production process of memory foam, the measured ILD and density ratings can change from batch to batch. It is not unusual for a foam that rates at 10lb ILD to vary between 8lb and 12lb.


This can also vary depending on the temperature and environment the foam has been conditioned in prior to testing.

All our mattresses are given an ILD rating of between 13lb and 15lb.

Memory foam mattress lifespan and care

Most good memory foam mattresses from reputable dealers will come with a long guarantee, Ergo Flex mattresses for instance come with a *10 year guarantee. But over that time, some natural sagging will occur. This is normal and to be expected. To help prolong the lifespan of your memory foam mattress follow the guidelines below.

Ergo Flex mattresses have three main component layers - the high density base foam, ‘cool sleep’ airflow system and the memory foam, so obviously flipping the mattress as you would with a sprung mattress is not necessary. Instead rotate it from head to toe every few months.

When you receive your Ergo Flex mattress, it will be vacuum packed and rolled up inside a cardboard box. Discard the box and carefully unroll your mattress. When opening your vacuum sealed mattress, take extreme care not to damage the mattress. You will probably need to use a sharp object to cut into the vacuum packaging - just be very careful you do not cut, nick or damage the mattress in any way.

Once you have opened the vacuum packaging, you will observe that the mattress is around only 3” deep. During the vacuum packing process, the mattress has all the air sucked out of it until it is the size you receive it at. This makes the delivery of the mattress to our customers simpler and more cost effective. Over the next 4 - 6 hours the mattress will 'inflate' to its true dimensions. You should be aware that once you undo the vacuum sealing, the mattress will also get a lot harder to move around - you will probably want to undo the packaging in the same room the mattress will be used in.