Hi Csj0952,
Many mattress manufactures are much better at making mattresses than they are at marketing, but I wouldn’t agree with you that their web site is “junk”. They provide general descriptions of the various lines they produce, but being a manufacturer there are hundreds of options they could produce, so it would be impossible for them to list all of their possible mattress permutations. As you are a distance away, a phone call certainly would be in order before making a trip.
Sleepmaster is a local factory direct manufacturer in Syracuse and Cicero, NY. They manufacture their own line as well as WJ Southard and Bemco mattresses. They make a wide range of all types of mattresses in a wide range of budgets from innersprings to memory foam to latex and use better materials and have better value than the larger manufacturers that are so common in the mainstream industry. Post #9 here will give you an idea of the type of experience you can expect there. I think highly of them and there are some good quality choices available here.
SleepEZ rates their firm Dunlop and Talalay at 37-40 ILD, and their Extra Firm at 44.
Nothing can replace your own testing and the comfort that you feel, as all of the layers of a mattress work together.
Polyfoam ILD (or IFD which is more commonly used in polyfoam) is measured differently than ILD in latex. Both use ILD/IFD at 25% compression (although some manufacturers use 40% ILD in Europe or Asia which would be different again) but with polyfoam it’s measured with a 4" layer which means that the IFD is the force it takes to compress the layer by 1" while latex ILD is measured on a 6" layer so ILD is the force it takes to compress the core by 1.5" (which takes more force). This means that polyfoam would actually be firmer in the same ILD than latex at compressions of exactly 25%.
In addition to this though … ILD is not the most reliable indicator of how soft or firm a layer will feel. Compression modulus is even more important because very few people actually sink into a layer exactly 25% and compression modulus is the rate at which a foam gets firmer as you compress it more. Latex has a higher compression modulus than polyfoam. In addition to this … latex is very “point elastic” which means that a smaller area can compress with less effect on or resistance from the surrounding area than polyfoam. This is much like the difference between pocket coils that act individually and innersprings that have helicals that join the springs together so that the compression of each spring will affect the springs around it which makes the spring stiffer.
In addition to this … latex has a lower hysteresis (how much energy is absorbed) and conversely a higher resilience (how much energy it returns) than polyfoam so there are also factors that can make latex feel firmer depending on how much a specific layer is compressed in a mattress. Because of its unique qualities and ability to take on the shape of the person on it (point elasticity) it can feel softer and firmer at the same time and some will feel it as one or the other depending on what they are more sensitive to, their body type, sleeping position, and how they sink into the mattress.
You may want to read through this short article of five steps to finding a mattress and some testing guidelines where I provide some general guidelines for that.
Phoenix