Hi Para,
Thanks for the link but unfortunately the article doesn’t say very much and really has very little in the way of specifics that would make the information practical so it’s not really all that helpful in “real life” because it doesn’t go far enough. It also has some misleading information when it comes to the softness of memory foam because there are many things besides the IFD of memory foam that will affect the softness or firmness of the memory foam and IFD itself isn’t a particulary useful spec with memory foam because it can change with time, heat, and humidity and memory foam IFD can also be very misleading if you use it to compare memory foam to the softness of other materials. The IFD of a single layer of memory foam is also only one of many variables that contributes to the firmness of a mattress itself.
There is more about the pros and cons of memory foam in this article and more about the different properties of different types and densities of memory foam in post #9 here and post #8 here and in the density guidelines here that provides more detailed and specific information that would be more useful as a guideline for the questions to ask (or what to test for when you are in a store) than the more basic and “generic” information in the article.
Phoenix