It's not hard. It's not at all like jello. Great support without being a rock! It doesn't hurt your joints.like I said for me it was perfect. I bought one then another and finally I bought the third one. I haven't had them long enough to know how they will hold up but I sleep in the same spot and it is never broken down. I will every few months rotate it as I do my mattress. Only because I do that.
For me it is perfect here in Tucson for the cooler winter nights and well into monsoon season! I read reviews before I purchased and read a couple where the guy said he had one better because he got too hot...can't imagine how that could be and now wonder if he was promoting his product..which does happen between Amazon competitors. (Kind of like restaurant #1 writing a bad review on his competitor (restaurant #2)).
I love this topper...no complaints, now had for 2 years!
I would guess to say that it's a medium firmness, I'm a 220 lb guy and it conforms slowly, especially when its cold, which is normally the temperature in my truck sleeper. But like I said in my review, it doesnt give you the hammock feeling that cheaper foams give you, your body parts sink down equally no matter their weight. I say that because regular foam doesnt give on your lighter parts, like when you lay your arm on it, it barely dents the surface, unlike this memory foam where you sink in and feel supported all over. Hope that helps.
A. INDENTATION FORCE DEFLECTION
The Indentation Force Deflection (IFD) number represents the pounds of force required to indent a foam sample by a specified percentage of its original thickness. This is measured with specially designed equipment. (Put "Indentor" transparency [T5] on overhead projector) In most cases, a 50 square inch round indentor plate is attached to a vertical piston-like cylinder having a precisely calibrated stroke.
Firmness is measured on foam samples having a square surface area of at least 15" by 15". Surface firmness is measured at 25% sample indentation (25% IFD). As an example, using a 4" thick sample, the 25% IFD reading would be made while the foam is indented to 3" height under the piston foot plate (25% deflection of the sample height).
B. SUPPORT FACTOR
Support (also known as compression modulus) is a key FPF property. (Put transparency [T6] "IFD and Support Factor" on overhead.) In many ways, it is the most important function foam can provide. In upholstery, good support from foam means that cushions don't "bottom out" or compress to a point where they no longer hold up the weight of a person. It also means that the cushion is capable of adequately distributing the weight of the person. As we have already learned, the most common foam specifications are density and 25% IFD (firmness). However, it is also possible to evaluate the deep down support of the foam. This is done by measuring the support factor, also known as "compression modulus".
Support factor is defined as the ratio of a foam's ability to support force at different indentation (or compression) levels. Support factor is measured by dividing the 65% IFD by the 25% IFD. These measurements for FPF typically range from ratios of 1.8 to 3.0. Two factors commonly affect the support factor. First of all, the higher the density of the foam, typically, the higher its support. Second, the foam chemical formulations and the manufacturing process often affect FPF support.
Foam producers can alter support by changing foam chemistry slightly during the manufacturing process. Specialty chemicals or fillers may be added or the manufacturing process may be adjusted.
C. HOW SUPPORT AFFECTS FOAM FUNCTION
Why be concerned about support? There are a number of reasons why different support levels can improve the comfort, support, or durability of finished goods using foam. In upholstery, support can affect a number of key design factors. Proper support enhances cradling, or the ability of the cushioning to distribute body weight and reduce pressure to the skin. Proper cradling distributes body weight so there are virtually no areas of body contact where the weight/load is concentrated to restrict blood flow and cause discomfort.
If cushions are thick, then softer, lower compression modulus foams may be used to improve cradling and to achieve more even distribution of body weight. If cushions are thin, higher compression modulus foams may be used to distribute the weight enough to prevent the cushion "bottoming out" against decking.
Seating systems -- foam, steel, springs, webbing, and fiber -- all soften with use. However, the specification of a higher support level can help cushions continue to feel "new" even after some surface softening of the foam and other materials takes place. This has the net effect of improving foam durability, an important feature of high quality foam.
It's also possible to laminate hard and soft foams together to improve the support of the composite foam structure. However, the difference between the firmness of the two foams cannot be too great, or the softer foam may seem to "bottom out" on the firmer foam.