Firmness rating of Memory foam
You may have read on numerous websites about the significance or firmness or comfort (alongside density) in choosing the ideal memory foam mattress. many go as far as to say that firmness is even more important than density. The truth is firmness is not a true indicator of quality. Not on its own, anyway!
Firmness is reached by an indicator called IFD which means Indentation Force Deflection. Another common term for it is ILD. You may have seen this before. It basically measures the amount of force, in pounds, required to make a 1-inch deep (3cm) indentation in a foam cube.
ILD ratings tell you how supportive a mattress really is - a major consideration for such a huge purchase that you hope will last 10 - 15 years or more. Unfortunately, ILD ratings are surrounded by smoke and mirrors and buyers never really know how to use them.
The Real Truth About Viscoelastic Foam ILD
A memory foam mattress is never 100% made from viscoelastic foam because it's not hard enough. In basic terms, it is made from a reflex foam core and a comforting memory foam softer layer on top. The ILD ratings of the various foam layers (you can have 2 or more) combine to give a mattress its actual firmness/comfort (or softness).
So you see, you cannot base your opinion purely on the ILD rating of the memory foam layer. This rating only tells you how soft the comfort layer can be. It can't and will not inform you how supportive the entire mattress really is.
There are various factors that affect mattress firmness and one of the most vital is its core. The memory foam top layer may be contouring and gentle even soft to the body but without a high quality, highly-resilient and firm core you will just sink right through the mattress.
While memory foam is not supportive entirely on its own to make a mattress purely from it, it does have some support of its own. You could say that it adds luxury and comfort as well as that extra bit of firmness. Careful, though! An overly soft comfort layer can create all sorts of problems!
A memory foam layer that's too soft and spongey can make the whole mattress feel uncomfortable and saggey. In other words, a low-quality top comfort layer can ruin an otherwise very good mattress. The answer?
Make sure the visco foam layer on top of the mattress is firm and supportive (12-15 ILD) as well as dense and sensitive to body temperature rises. The ultimate test, however, should be your own personal comfort and choice.
For more on mattress firmness, including memory foam tips, go to www.mattressnextday.co.uk