Mattress Forum

Not so much the material itself but the support it gives in the softer ILD's very well could be. An HR poly foam with the same qualities (ILD and support ratio) would have the same issues.

From everything I know and based on the people I've talked to that know a lot more than me, back issues have very little to do with firmness or softness per se ... even though it's a common misperception. It has much more to do with how well the back is aligned when you are sleeping and misalignment ... and back issues ... can happen with any firmness of mattress.

The days of "firmer is better" are long over ... thank goodness lol

I'm glad you sold your mattress ... and good luck with your next one!

Phoenix

In actuality the density of the foam will dictate the level of support.  A higher density medium will by default be firmer.  The compression of springs and the compression of latex is not the same.  My suspicion is that latex is creating pressure points by the way it compresses...

So if you were to take a piece of say energia foam with properties (ild and support ratio) the same as a piece of latex, the back issues would be the same, even if the densities were different. In other words they would feel identical and offer the same level of support.

Phoenix

I really don't care what the ild is.  My point is that there are differing types of compressibility, i.e., linear, progressive, etc.  My suspicion is that the compressibility of latex is the problem.

When I say density I am not refering to jello or styrofoam, I am speaking in context of latex foam...

Anyway no longer matters, we are rid of the mattress, took a bath on it and learned a very valuable lesson!!!

In any case, I'm glad you're half way to solving your back pain issues. Back pain is never fun no matter what the cause.

Phoenix

We are using compressibility differently, I am using it in engineering terms, you are using in industry terms.  The industry terms do not take into account spring type i.e., is the spring a linear spring, or progressive spring, etc.  I suspect the spring type approximated by latex is not always bio-compatible.

To answer your questions again

I tried very firm latex

I tried very firm latex with a 3 inch topper

I tried very soft latex

There are 120 permutation of these 6 slabs of latex in a 3 layer subset. Plus the various permutations of toppers (latex, fiber, memory foam) I had the same back problems with all configurations, there is no "easy" solution to this problem  I spend 18 months trying all of the compunations and permutations.

I refuse at this point to spend anymore money on a problem with a suboptimal solution (or better yet unsolvable).

Many thanks, but I am done with trying to make latex work.  It was a very expensive lesson, but well learned...

Phoenix, so what is the value of having higher density?  It seems like it is easier to get more support, because you are working with more "stuff".  As a general rule, the higher density foams (latex, high quality MF) seems to have more support than the lower density foam/versions.  Of course, they can make firmer and more supportive versions out of less dense foams, but maybe they just don't last?  Perhaps when they use a lower density foam they have to cut a corner somewhere (resiliency or something else)?

Where did you learn so much about the foam/mattress industry?

3 lb memory foam will usually not usually last as long as 5 lb memory foam (of the same type).

1.8 lb HD foam will not last as long as 2.5 lb HD foam (again of the same type). Notice here that anything in a poly foam above 1.8 is usually called HD (High Density) while in other foams (memory foam for example) this would be ridiculously low.

HR foam means high resiliency which means it can be compressed and come back more readily and more often (not as prone to holding an impression). It is generally considered to be the best of the poly foams. There is a lot of research going on to make HR foam with qualities and durability that mimics other foams (latex for example) or that has certain desireable qualities.

Also ... if you are comparing the same materials, a higher density will have a higher ILD (measuring the initial weight it takes to compress a foam down 25%). Typically these measurements are done on a piece of foam 4" thick and at least 20" x 20" and the force is applied with a round 50 sq in deflector foot. Different foam thicknesses, sizes, and percentage compressions as well as many other factors will lead to different numbers so this is the "sort of" standard but it is not completely definitive.

A really great discussion of this and the huge number of variables that can be involved in ILD (for those so inclined) is here (the pfa or polyurethane foam association is a great resource) http://www.pfa.org/jifsg/jifsgs4.html  ILD and IFD are the same thing with a different name.

Support factor (also called support ratio or compression modulus or comfort factor) is discussed here http://www.pfa.org/intouch/new_pdf/lr_IntouchV3.1.pdf

I'm glad you asked this too because I just realized that the support factor is a ratio between 65% and 25% and not 75% and 25% as I have been saying earlier. There are some sites that talk about it as 75/25 but the pfa is the "authority" so I have learned something today that I never noticed before lol.

Anyway back to your question, when you are comparing different materials, density does not have nearly as much value and really doesn't say much at all about either comfort or support. For example a 3 lb HR foam will usually last for a very long time and is considered very dense and firm while a 3 lb memory foam will usually wear out (or lose it's properties) much more quickly and is considered very soft. Both memory foam and latex are common in around the 5 lb range and yet the latex is much longer lasting and offers much more support. So density only really says how much a cubic foot of material weighs and little about the qualities of the material itself.

Density is only really good as an indication of the relative durability and longevity (and in most cases firmness) of 2 pieces of foam of the same material

As to your last question ... When I'm interested in something I read a LOT. I tend to be a "researcher" by nature and enjoy the challenge of getting to the bottom of things. Sometimes getting to the bottom means falling into a never ending pit though (laughing).

Phoenix

Do you have a reference chart that shows support factors for a lot of different types of foam?  Latex vs. various PU vs. memory foam etc.?  Of course it will vary from product to product,  manufacture to manufacturer, etc.  But would be nice to have a general guide.