Foam is the most common form of comfort layer used in mattresses. There are many different types and qualities of foam, so when you are shopping for a new mattress, be sure to look for mattresses that use high quality foam grades.

Foams are graded by their Density (weight) and Hardness (or softness).

Foam Density
The density of foam refers to its weight per unit of volume. This is often quoted as kg/m3. Density is important because it relates to foam’s ability to perform in its application. It is possible to have two foams with the same softness but differing in density; the higher density foam will outlast the lower density foam and will not lose its loft (height) as quickly.

Hardness (Softness)
"Hardness" is used to describe the way a foam feels and should not be confused with density. The lower the density of the foam the more it will tend to "bottom out" under heavy loads, where as the higher density foam with the same hardness will be able to support heavier loads without "bottoming out". This means there is less chance of feeling the springs through the comfort layers. 

Latex is first made of millions of tiny latex bubbles and during the final stages of its production process, all the bubbles (cells) open up and foam.  These opened bubbles are called “Open Cell”.  The open cell structure is so unique that there is no air trapped within the cells.  One of the advantages of this open cell structure is that body heat will not be trapped in an air pocket like within a closed cell.  Therefore it is cooler and more comfortable throughout the night.  Another advantage is that vibration is easily absorbed and disturbances are reduced to ensure a quiet and comfortable night’s sleep. Superior comfort and lasting orthopaedic support are maximised by the fact that natural latex adapts to your body weight and contours to your body thus becoming more comfortable as time goes by.