Question on foam core in a latex hybrid

[phoenix]

Hi beanbag,

That got me wonder, what was the point of having a big 8" chunk of foam if it is going to only compress that little? And then I was worried if it would create the sensation that you only get 3" (+ quilting) worth of “suspension travel” from the top latex layer before you hit something hard.

The thickness of a foam layer has as much effect on how it compresses as the firmness or softness (ILD) of the layer as well as some of the other foam specs including compression modulus and point elasticity. All the layers of a mattress and all the parts of each layer compress simultaneously and not independently of each other. Each layer and each part of a layer will compress proportionately and not just sequentially. Foam gets firmer as you sink into it more deeply depending on the type and thickness of the foam and on some of its other properties or specs and thicker layers get firmer more slowly and have a greater range of compression from softer to firmer before they bottom out (can’t go any firmer) than thinner layers. You can read more here about the effect of thicker layers in post #14 here and there is also more information in post #4 here about some of the different foam specs that affect the perception of softness, how deeply you sink into a mattress, and how a mattress will feel and perform under different body types. All of this is part of the art and science of mattress construction. If you used a 2" polyfoam base layer under memory foam of the same firmness as an 8" layer of the same material it would be much less adaptive and feel much firmer even if the memory foam layers are the same.

BTW, I am only 150 lbs, so I am not really worried about crushing thru the top 3" layer, but I imagine that one of the things that makes an all-latex mattress nicer was that you can continue to have compression beyond the first few inches. Would the cheaper 1.5 foam actually feel closer to all latex?

No … some higher density polyfoam called HR polyfoam (which is in the range of 2.5 lbs and higher, has a compression modulus of 2.4 or higher, and has about 60% resiliency or higher) will have some of the feel and response of latex but density is mostly about the relative durability of a foam and any density of polyfoam can be made in a wide range of firmness levels from very soft to very firm.

While polyfoam is also a fast response material like latex … they are quite different in how they feel and perform. There is more in post #2 here about some of the differences between a latex hybrid and an all latex mattress.

Phoenix