Hi Jtat84,
Their comments are really bringing up two separate issues. One is about the suitability of a mattress and the other is about the durability of the materials inside it.
I would keep in mind that primary support comes from the deeper layers of a mattress not from the upper layers which are for pressure relief and secondary support. Careful testing using the testing guidelines in the tutorial will give you the best chance of knowing which mattress is the most suitable choice in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) for you without having to know the “why” behind the “what” … but if you are interested there is more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel”.
Outside of the suitability of a mattress they also brought up the issue of the durability of 100% natural Talalay latex which is something different from PPP. While all latex is a very durable material compared to other types of foam … they are correct that Latex International’s 100% natural Talalay is less durable than their blended Talalay version … particularly in lower ILD’s. There is more about the difference between 100% natural Talalay and blended Talalay in post #2 here.
Dunlop and Talalay aren’t directly comparable in terms of firmness using only ILD numbers because there are several factors that can affect how soft or firm a mattress (or an individual layer) feels besides just the ILD of the material (see post #4 here) and Dunlop and Talalay that are the same thickness and ILD won’t feel the same in terms of their firmness for most people because they have a different response curve and compression modulus (how quickly a material becomes firmer as you sink into it more deeply). There is more about the difference between Dunlop and Talalay in post #7 here.
In addition to this all the layers and components of a mattress will have an effect on all the other layers and on the mattress “as a whole” and one of the mattresses you are considering has an innerspring support core and the other one has a latex support core so this will have a significant effect on how they compare even if the top 3" of each of them were very similar in terms of firmness. There is more about the differences between an all latex mattress and an innerspring latex hybrid in post #28 here.
The ILD of different materials or different types and blends of latex also aren’t always directly comparable to each other (see post #6 here) partly because ILD can be measured in different ways and partly because ILD isn’t the only factor that affects the softness or firmness of a material so again using the ILD or other specifications of a particular layer or combination of layers as a reliable indication of how any mattress will “feel” or how firm it will feel to you compared to another mattress with a different combination of layers can sometimes be more misleading than helpful.
The most reliable way to know how two mattresses compare for you (regardless of how they would compare for someone else) is based on your own personal testing and experience and the most reliable way to know how two mattresses will compare in terms of durability is based in knowing the type and quality of the materials inside it. There is more about the many variables that can affect the durability of a mattress relative to different body types and weight/BMI ranges in the durability guidelines here.
Having said all that … Neal at Spindle will be able to give you good information about how the firmness of each of their layers roughly compares to various Talalay ILD’s.
Mountaintop uses two different methods to test their ILD ranges. One of them is the amount of force it takes to compress the material by 25% and the other is the amount of force it takes to compress the same material by 40% (which of course would produce higher numbers).
Their 25% ILD ranges are …
C0 9.5 - 12.5 ILD
C1 11.5 - 14.5 ILD
C2 17.5 - 20.5 ILD
C3 21.5 - 24.5 ILD
C4 29.5 - 32.5 ILD
Their 40% ILD ranges are
ILD Range
C0 14 - 20 ILD
C1 18 - 22 ILD
C2 27 - 33 ILD
C3 34 - 42 ILD
C4 44 - 54 ILD
The closest ILD approximations to Talalay for each of their different firmness levels for individual layers would be somewhere in the lower end of their 40% ILD range.
Phoenix