6 inch Latex Mattress

Hi Dan1979,

There are many ways to rate the firmness of a material around the world but in the end it boils down to what you feel because there are so many factors beside the “rated” firmness of a mattress or a particular layer (regardless of how it is measured) that can affect how a mattress feels and performs for you. Posts #1 and #2 here would be well worth reading but translating from one type of firmness measurement to another can be difficult, involve several steps, and would require knowing the percentage of compression that was used to rate the material for firmness (usually either 25% or 40%).

I don’t know who may be manufacturing or fabricating latex in Bulgaria but it could be a division of Sapsa in France, or Artilat or Latexco in Belgium which are all large European latex manufacturers.

1 kpa (kilopascal) is the same as 0.145037738 psi and ILD is measured with a 50 sq in foot so 0.145037738 x 50 = @7.25 lb. If the testing used the same compression percentage (either 25% or 40%) then 1 kpa would equal 7.25 ILD and 4.8 kpa would equal @ 35 ILD. It would be very important though to make sure that both materials you were comparing measured ILD at the same compression percentage or the comparisons would be meaningless and if the compression modulus of each material was different then the comparison would only apply if you compressed both materials to exactly 25% (no more and no less).

In other words … without comparable “specs” on both sides of a comparison you are better off using your own personal testing or experience to compare different materials.

There is a density converter here which you can use to “translate” one density measurement to another that is more commonly used on this site. 50 kg/m3 is the same as 3.12 lbs / ft3 which for memory foam would be lower quality. 30 kg/m3 is the same as 1.87 lbs / ft3 which for polyfoam is good quality.

This would generally be in a soft range (you can see here for an approximate density / ILD reference point for 100% natural Dunlop). Synthetic rubber is less dense than natural rubber so the percentage of a blend would have an effect on the comparison and different compounding and production methods will also affect the ILD/density of each material to some degree.

Yes … this would be inside the range of “normal” experience although the reasons “why” you are experiencing what you are experiencing may or may not be accurate. You may feel pressure on your lumbar for example on a firmer mattress because your upper body doesn’t sink in enough for your recessed lumbar to make firm enough contact with the mattress which can feel like pressure when it could be muscle tension that comes from the muscles holding your lower back in alignment instead of the mattress. Either way I would trust your own personal experience. Side sleeping generally needs thicker softer comfort layers to relieve pressure than back sleeping so a design that works well for side sleeping can sometimes cause alignment issues for back sleeping.

Synthetic rubber has a lower density than natural rubber so the same ILD in both (assuming that ILD or firmness is tested with the same method) will have a different density. RG60, RG65, RG75 and and RG 80 sound to me like density ratings (60 - 80 kg/m3) with a range of variation that can be expected in each rating. Density/firmness comparisons between types of latex that have a different blend of natural and synthetic probably won’t be accurate.

There is nothing “wrong” in your experience and I would always trust your own experience over “theory at a distance”.

Latex and memory foam all come in different types and firmness levels so if a particular mattress is a good “match” for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) in all your sleeping positions then all that’s left to do is to make sure there are no obvious weak links in the mattress in terms of durability and that you have enough information to make meaningful comparisons to other mattresses that are also a good match in terms of PPP.

Yes … making any change to a mattress design will have an effect on how the mattress feels and performs. The glue won’t make it less durable. The “safety” of the glue would depend on the type of glue that is used but if it’s a latex glue rather than a solvent based glue then it would generally be considered to be safe. If the 3" layer of latex is the same firmness as the 16 cm layer of latex and the glue was flexible rather than firmer then the two glued together would be about the same firmness level as a 19 cm core of the same material that had the same firmness rating as the two layers glued together. If the top 3cm layer of added latex was either softer or firmer than the 16 cm layer then it would affect how the glued combination compared to the unglued layer.

That’s a lot of technical questions and using detailed specifications to choose a mattress instead of a simpler process based on yoru actual experience can easily lead to information overload but hopefully this has been helpful.