So I am currently having my first experience with latex which I like even though I don’t think the mattress itself is the right fit. I am thinking I might make a go at doing something myself or at least ordering something that can be customized. For the sake of simplicity I will stick to talking about dunlop since it’s more likely to be the direction I head, not that I am super budget limited either.
I was looking at a comfort layer of D65 density dunlop but was debating going with either 3 inches of this or going with 2 inches and then having another 2" underneath it of a medium dunlop, like around D75 or D80. All of this would likely go over a pocket coil system. So basically either 3" of latex all at D65 or 4" of latex with half D65 and the other half D75/80. I am not very heavy (under 150lbs) and like the idea of two 2" layers as I feel they give me more flexibility down the road, like if I wanted to try a 2" talalay layer at some point which I could put over one of those layers and still use the same encasement. I guess my question is would I be adding a significant amount of firmness to the mattress going with the 4" half and half approach vs 3" of only soft or would the added inch of latex balance some of that firmness out?
Also sort of related but unrelated but how much of a difference does latex type make in lower support layers? Obviously the top layer would be very noticeable between dunlop and talalay but if the layer underneath it were of similar firmness say a soft dunlop or medium talalay would there really be that much of a noticeable difference since it would already be under 2-3" of another layer of latex?
If you are thinking about designing and building your own DIY mattress out of separate components that are purchased from one or several different sources then the first place I would start is by reading option 3 in post #15 here and the many posts it links to (it’s a bit of reading, but really is worth it to spend some time delving into those posts and links) so that you have more realistic expectations and that you are comfortable with the learning curve, uncertainty, trial and error, or in some cases the higher costs that may be involved in the DIY process.
Your question doesn’t have an exact answer, as quite a bit of this comes down to your personal preferences and perceptions, and your own definition of what might “balance out” one configuration versus another. But I can provide some general information, without getting too technical.
The 3" of plush D65 Dunlop would generally be near the maximum range I’d recommend for a side sleeper, but this is of course a general recommendation. You are correct that using two 2" layers will offer you more versatility and going with D65 over D75 would be a bit more of a “typical” configuration. Which might feel best to you would of course be determined through your own personal testing. While Dunlop does have a higher compression modulus than Talalay and the D65 in 3" would “firm up” more in areas compressed more than 25%, it would not feel as firm overall as the D65/D75 combination you mentioned.
There’s really no way to know unless you’ve tested similar reference mattresses which contain similar combinations of materials if you might prefer one of these combinations over the other. All of these layers (including the pocketed spring unit) will compress simultaneously and they will each compress to different percentages of their thickness depending on their position on the mattress, the firmness of each layer, the compression modulus of the material, the thickness of each layer, and the compression force that they are exposed to (which depends on the weight of the part of the body in contact with the mattress and the surface area that is bearing that weight which is constantly changing as you sink into the mattress more or change sleep positions).
Even the softest latex won’t tend to “bottom out”, but you may tend to “feel through” the softer D65 3" layer to the transition to the innerspring unit, versus the D65/D75 combination where the materials may “bend into” each other a bit more gradually.
Without personal testing and going through the learning curve of becoming familiar enough with different types of materials and layering and how they work in combination with each other to predict how a certain layering may work, I often suggest going with the suggestions of a knowledgeable retailer or manufacturer who is familiar with how the different options they offer fits the “averages” of people who may be similar to you, or mimicking combinations that you’ve tested and are currently offered by other manufacturers. While the question you asked seems simple on the surface, it actually is quite complex and there are experts within the industry who spend their lives analyzing how different layerings work together. Being able to rearrange layers, as with the D65/D75 example, while it does introduce extra variables into the equation, does give you more options to “fine-tune” your design.
You’re correct that there is less noticeable difference in surface comfort the farther away you are removed from the uppermost layers. Differences in the second 2" layer in your example will definitely be noticeable, but will not have as great of an impact in initial comfort as a change in the uppermost layer.
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 be helpful in clarifying the difference between “support” and “pressure relief” and “feel”.
Thanks, definitely a lot to read and think about. Dunlop seems especially confusing as SleepOnLatex says their soft is D65 and D80 is medium whereas FoamOrder says their soft is D60 and medium is D70 with D80 being firm. I know firmness is all relative but it seems strange to have one topper with a density of 80 being called medium and another call it firm. Is it just that each site has a different concept of medium or is it in fact possible for two pieces of latex with the same density to have very different levels of firmness?
Added: I just found an old post of yours that I think says Dunlop densities are rated by the entire 6" core they come from and not the topper layer itself. Maybe I misunderstood it but I imagine that could explain how D80 could mean both medium and firm if the medium came from the top of the core and the firm came from the bottom? FoamOrder says they get their latex from Arpico and it seems most other stores that use Arpico use similar descriptions when describing firmness levels of each density. SleepOnLatex doesn’t say who makes their latex (maybe Latex Green given the Pure Green branding?) but I guess it could be that their toppers always come from the upper half of the core hence explaining how their densities don’t match up with the firmness levels of latex from Arpico?
“Word definitions” are just what a retailer or manufacturer decides to use as a descriptor of their foam relative to their other offerings, and are not meant to be accurate cross-comparisons set to definitions which of course couldn’t be standardized. Density and hardness (ILD) have an almost direct relationship in latex, and relating densities across brands is the easiest way to compare one item to another. Many mattress manufacturers will relate the “word definitions” that the latex pourer provides of the foam instead of the densities, as these “word definitions” would more easily “make sense” to the general public. Realize that a density of a foam core will fall within a certain range, and there can be subtle differences in the feel of similar densities based upon formulations, production processes and fillers.
The density is measured from the 6" Dunlop core (there are some 3" cores poured by they are not as common in Dunlop), and it is true that the uppermost layers slit from the core can have a softer feel than the deeper layers, but if foam was slit from a D85 core, it will be call “firm” (as an example) whether or not the piece was from the top, middle or bottom. There are some mattress manufacturers who will attempt to “match up” pieces from similar molds or runs or positons from where they are slit when a client is ordering two of the same type of foam for a mattress, but this is not normally the case, as all densities are within a range and there is variance to begin with regardless.
And if you are comparing two specific products, the density numbers are the most accurate way to compare for Dunlop latex, but you may also wish to phone the mattress company and tell them what other items you are considering and most likely they will know how their foams compare to that other offering.
I hope this information is helpful to you. I’ve attempted to answer your questions without getting too technical, which I know at times can only make things more confusing. :S