Hi hiddenspring,
Celsion is the old name for what Latex international now calls Talalay GL fast response and Pure Latex Bliss calls Active Fusion (although Active Fusion also refers to their cover which also has phase change materials in it). The type of materials (blended Talalay and Talalay GL fast response) in the PLB lineup are the same in the Healthy Back but the design and layer thickness or firmness of the layers may be slightly different between them (see post #16 and #17 here)
With polyfoam … density is unrelated or at best very loosely related to ILD because any density of polyfoam can be made in any firmness level. Density is a quality spec not a comfort spec and is one of the most important parts of the durability of a polyfoam layer but has little to do with firmness/softness.
With memory foam … ILD is not very relevant at all because it changes in response to temperature, humidity and time and memory foam ILD’s are not a reliable spec with memory foam. Based on ILD alone … they are all “soft” although memory foam doesn’t always feel as soft as the ILD would indicate. With memory foam as well … density is the most important part of durability not softness or firmness. Any density of memory foam can have different response rates, temperature sensitivity, or tested softness levels and how a memory foam layer feels can also be highly affected by what is over or underneath it in the mattress.
With latex … ILD is directly related to density and some manufacturers don’t even test their latex for ILD and only provide density numbers to indicate firmness.
In addition to all of this … ILD by itself is not a reliable indicator of how soft or firm a specific foam will feel because it is only measured at either 25% compression or 40% compression and different materials are tested for ILD on different layer thicknesses. Other specs including layer thickness and compression modulus (how quickly a foam get firmer as you compress it more deeply) and the compression curve of a material (they don’t usually get firmer in a linear progression) are all just as important as the ILD of a material. All the layers in a mattress interact together and affect each other in other words. Post #2 here has more detail about some of the many specs that can affect the feel and performance of a mattress.
When you are testing a mattress locally … then ILD information is mostly meaningless because good testing will tell you what you need to know about a mattress in terms of PPP (Posture and alignment, pressure relief, and Personal preferences) more than any ILD information which is really not relevant unless you are trying to duplicate a mattress. The information that is most important when you are testing a mattress is the quality specs which for polyfoam and memory foam are density and for latex is the type and blend of the latex.
There is also more about ILD’s and different types of testing and comparisons between different types of foam in post #6 here and in post #4 here. In most cases … ILD comparisons are only relevant if they are accurate (which is not always the case), measured in the same way, and between the same type and/or blend of material, and they don’t compare specifically across different materials or even variations of the same material (such as latex).
The density of latex (either Talalay or Dunlop) is not an indication of its quality (unlike polyfoam and memory foam) and is neither good or bad … it’s just a side effect of the firmness of the latex layer.
You can read more about the different types of latex in post #6 here and post # 6 here and while personal experience is really the only way to know whether you prefer Dunlop or Talalay (it’s strictly a preference choice in other words) … you can read a little more about how they compare in terms of “feel” in post #7 here but I would trust your own perceptions over anyone else’s description because much of this is subjective and can vary from person to person.
You can read in post #2 here why “theory at a distance” based on specs is not a reliable way to design or choose a mattress and it also has some links that can give you some insights into some of the many variables involved in mattress design but these can be much more complex than is necessary and in general terms I would keep things much more simple than trying to use complex combinations or specs or “theory” to design or choose a mattress. With latex the choices would be more about firmness than density (except in the case of some Dunlop layers where density may be the only spec available that indicates its firmness range).
Phoenix