i know too low a support factor can make you “fall through” the foam and “bottom out”
but can too HIGH support factor be a problem ?
according to my calculations 65% divided by 25% is 2.6 which means that if you were to float in a liquid like water in which pressure is proportional to depth - you would experience a support factor of 2.6
most foams would be lucky to reach 2.6 support factor but some go ABOVE that, and i have to wonder - if that would be detrimental ?
and on a related note - it seems we layer lower ILDs on top and higher ILDs on the bottom to compensate for lack of progressive resistance of foams with support factor around 2.0 or so. but with high support factor materials like Latex i think such layering could become detrimental ? a uniform ILD from top to bottom might be better ?
a higher ILD top layer would not bottom out on the lower layers and allow for a lower ILD lower layers so it might actually provide better pressure relief - no ?
specifically Pure Latex Bliss felt too progressive to me - a soft surface that you fall right through and then land on some deeper layers.
i’m just thinking out loud, sorry, i wish i could actually understand what i am saying
This would depend on the application and on the specifics of the design and the person sleeping on it. For example … for some people a Dunlop comfort layer of a certain ILD may be too firm while a talalay layer may be fine because Dunlop has a higher support factor than Talalay (gets firmer faster). The advantage of a higher support factor is that you can use a lower ILD than you otherwise could and it will “catch up” to a material that has a lower support factor and higher ILD as it compresses so you would have a deeper “ride”.
Actually buoyancy works very differently from foam compression and is related to mass/volume while compression is related to force/surface area.
Again …there are no rules here but only what works best for each individual. In some cases a single 6" layer of soft Dunlop can work very well for the reason you are describing but most people seem to do better with some type of separate comfort layer. This is all personal preference though and if a mattress provides someone with the PPP (Pressure relief, Posture and alignment, and Personal preferences) that works best for them then the “theory” behind it is not really relevant.
No it doesn’t work that way. It may provide a better “feel” for some people but in general terms softer materials provide better pressure relief because they provide a greater depth of cradle and re-distribute pressure across a wider surface area. All the layers compress together although they do so to different degrees so even soft materials aren’t likely to "bottom out’ if they are on top of other layers that are also compressing (other than the floor) but they can certainly allow someone to “go through” them enough to feel any firmer layers below them.
I’m not sure that “too progressive” would account for what you are feeling and you may be overanalyzing here. If anything this would not be “progressive” enough meaning that the transition between layers could be too abrupt. It would also depend on which of the PLB mattresses you are meaning because they are all very different. You could also try the Nutrition which has a dominating layer (firmer over softer) to see how you like it though.
Some of these things can be “counterintuitive” but I’m impressed that you have some of the understanding you do … although a little knowledge when you are dealing with a very complex subject can sometimes be a dangerous thing
“The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.”
~ Stephen Hawking
“There are known knowns; there are things we know we know.
We also know there are known unknowns; that is to say, we know there are some things we do not know.
But there are also unknown unknowns – the ones we don’t know we don’t know.”
