Hi ikonos,
There have been quite a few discussions recently about ILD and how it relates to latex, but especially Dunlop latex. In essence … most Dunlop is made to density not to ILD and the ILD translations are in some cases all over the map and just guesses. Both Talalay and Dunlop layers and cores have a variety of ILD’s across the surface which can vary from spot to spot over the surface of the material but in general Talalay has a narrower range of ILD variance while the variance in Dunlop can be more (and can also vary from top to bottom). In other words … “exact” ILD’s don’t really exist in either material and it’s best to think of each core or layer as a “range” rather than a specific ILD but the range of variance in Dunlop is more than Talalay. The most accurate way to compare Dunlop of the same blend would be by comparing density (usually expressed as kg/m3) and 100% natural Dunlop would typically be in a firmness range of about 65 kg/m3 to about 95/m3. There are also some differences in different Dunlop formulations that can also have an effect on the range of ILD’s of Dunlop made by different manufacturers even in the same density but the most accurate comparison method would usually be density.
You can see some rough comparisons between Dunlop density and ILD in post #2 here.
This variance in ILD could be part of why the Dunlop felt softer to your wife than a similar ILD Talalay. Different people feel things differently as well so this could also just be a difference in subjective perceptions because of the time in between testing each (most people don’t remember subjective impressions very accurately). Dunlop has a higher compression modulus than Talalay (because it is denser) which means it gets firmer faster with deeper compression than Talalay. The “equal” point between them (if they both have the same ILD) is 25% compression and with more compression than that Dunlop would be firmer meaning that it would take more weight to compress it as much as Talalay. Less than 25% compression would mean the Dunlop was softer than the Talalay but most upper layers are compressed more than 25%.
The Seattle Mattress site says that they use a natural fiber fire barrier which would normally be wool but they don’t say that for certain. I’m sure they would tell you if you called them.
Most of the choice between Natural Talalay, Blended Talalay (which is what Seattle Mattress is using), and Dunlop is really a matter of preference. This page along with post #6 here has more about the different types and blends of latex. If you are interested in the more technical aspecs of NR (natural rubber) and SBR (synthetic rubber) then post #2 here and post #2 here go into a great deal of detail and have some links with more detail yet.
The “most” natural of the latex varieties would tend to be 100% natural Dunlop.
100% natural Talalay is a more expensive material and is slightly less pressure relieving and in the lower ILD’s is potentially less durable than the blended Talalay. both are Oeko-Tex certified which means they have been tested to the same standards (standard 100 class 1) for harmful substances and offgassing.
If someone wanted a 100% natural Talalay latex for it’s own sake and the possible lower durability (in lower ILD’s) and higher cost wasn’t important … then it would make a good choice for their particular “value equation” (the things that are worth paying for and most important to each person). In Dunlop … 100% natural is generally considered a better product in terms of durability and performance than a blended Dunlop.
Talalay and Dunlop also have a different “feel” with Dunlop being denser and less lively (think angel food cake vs pound cake) and Talalay being more “springy”. This is primarily because it has a lower density and a different more round cell structure. There is more about the difference in “feel” between the two types of latex in post #7 here.
So the best “value” in latex, at least for most people, would tend to be either blended Talalay or 100% natural Dunlop. I would make the choice between the different “good” options (natural and blended Talalay and natural Dunlop) based on what was most important to you and on which “feel” you preferred.
I hope I answered most of the questions that you seemed to be thinking about but if I’ve missed anything feel free to ask.
Phoenix