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Calculating density and other questions 08 Oct 2013 01:39 #1

Hello,

First off, I'd like to thank all the people that have worked on all the info that is provided on this site. I live in Greece, and there is virtually no site to gather information nowhere near this extent. Some topics on some forums where 'anyone' could give an opinion. I was watching a youtube video from beducation and they mentioned this site.

I couldn't get memory foam / latex densities in the articles ( Latex , Memory Foam )

After some searching I came up with the following info, but not sure how accurate they are.
LATEX / MEMORY FOAM DENSITY
GRADELBS/FT^3
Lowx < 4
Mid4 < x < 5
Highx > 5

Questions
1) Would Dunlop and Talalay have the same density ranges. For example, let's say we have a 28 ILD Dunlop / Talalay. Would both pieces be of the same density?
2) If mattress cover is 100% natural cotton are mattress ventilation holes necessary? (Supposedly cotton allows mattress to breathe)
3) Perimeter support (within mattress structure): what type and how hard of foam? What other options, material wise, are there?
4) Adjusting bonnell spring height , depending on the thickness of comfort layers; would mattress properties change if we asked for coils height to be adjusted (higher or lower)?
5) As mentioned in one of the articles, an all-latex mattress can vary in thickness from 6” to 11” (depending on person's weight). What about an all-HR foam mattress? Same mattress thickness?

On this side of the world, some companies use kPa (Kilopascal) instead of ILD/IFD to measure hardness of a foam mattress. In search of a way to convert from one to the other, I came accross this site: http://www.europeanbedding.sg/density-hardness-resilience-weight-of-latex-mattresses-a-40.html#.UlJx6VBkOSo

According to the site,

1 ILD = 0.14 Kpa or 1 Kpa = 7.14 ILD
In general we can say a
soft mattress : +/- 3.5 kPa
medium mattress : +/- 4 kPa
firm mattress : +/- 4.5 kPa


Also,

Using the length, width, height (thickness) and density of the mattress, we can easily calculate the weight of the mattress. For example, for our EB Back Care Perfect King Size latex mattress, the latex core length is 2m, the width is 1.8m and the height is 0.18m. Let’s calculate the weight of;
firm mattress : – 2 x 1.8 x 0.18 x 75 = 48.6kg
medium mattress : – 2 x 1.8 x 0.18 x 70 = 45.36kg
soft mattress : – 2 x 1.8 x 0.18 x 65 = 42.12kg


6) Do you happen to have a source to verify the above findings?
7) If what is mentioned in the 2nd quote stands, then if we knew the net weight of the mattress (approximately) we would be able to calculate density. Is it really that simple? Or is it another made up story to confuse consumers?
7a) Could the same be applied to a polyfoam mattress?
7b) Could the same be applied to a single layer?

Thank you for your time

k3rb3r05

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Calculating density and other questions 08 Oct 2013 11:44 #2

Hi k3rb3r05,

Welcome to the Mattress Forum! all the way from Greece :)

After some searching I came up with the following info, but not sure how accurate they are.
LATEX / MEMORY FOAM DENSITY
GRADE LBS/FT^3
Low x < 4
Mid 4 < x < 5
High x > 5


This would be roughly accurate in terms of durability. Higher density memory foam is more durable up until you reach about 6 lbs or so and beyond that the benefit of increased density is reduced. This also isn't connected to the properties or "feel" of the memory foam though because different chemical formulations can change the properties of memory foam even in the same density. there is more about this in post #9 here and post #8 here . There are many people who prefer lower density memory foams because they may "feel" better even though they are less durable.

1) Would Dunlop and Talalay have the same density ranges. For example, let's say we have a 28 ILD Dunlop / Talalay. Would both pieces be of the same density?


No ... Dunlop has a higher density than Talalay in the same ILD. It wouldalso depend on whether the latex was natural or synthetic because natural latex has a higher density than synthetic. Dunlop also has a higher compression modulus which means that it gets firmer faster with deeper compression than Talalay so they are not really comparable in terms of softness even if the ILD is the same. There is more about ILD comparisons in post #6 here and you can read more about the different versions of latex in post #6 here . there are also some density / ILD comparisons between Talalay and Dunlop in post #2 here .

2) If mattress cover is 100% natural cotton are mattress ventilation holes necessary? (Supposedly cotton allows mattress to breathe)


Even though latex is a more breathable type of foam than most polyfoam or memory foam ... the pincores can still add to the breathability of the layer because all foam ... even latex ... is an insulator and not as breathable as natural fibers. there is more about the factors that are involved in temperature regulation and the role of moisture wicking and airflow in post #2 here .

3) Perimeter support (within mattress structure): what type and how hard of foam? What other options, material wise, are there?


This is generally only necessary with innerspring mattresses not with foam mattresses but there are still people who prefer it even with memory foam or latex. There is more about edge support in post #2 here and in post #33 here . In many cases foam surrounds are a way to lower the cost of more costly materials (such as latex or steel).

4) Adjusting bonnell spring height , depending on the thickness of comfort layers; would mattress properties change if we asked for coils height to be adjusted (higher or lower)?


It's not generally possible to choose an innerspring with a different height where all the other specs of the innerspring are the same. If all the specs were the same though and the ONLY difference between the coils was the height then the coil would be firmer because the pitch of the coils would be greater. Whether this was better or worse for you would depend on the design and materials in the rest of the mattress.

5) As mentioned in one of the articles, an all-latex mattress can vary in thickness from 6” to 11” (depending on person's weight). What about an all-HR foam mattress? Same mattress thickness?


There really isn't a standard thickness for a latex mattress and I've seen them as thin as 4" and some as thick as 16" (although the range is typically in between 6" and 12"). A mattress can be as thick or thin as a manufacturer wants to make it and the thickness of each layer or the thickness of a whole mattress is only one of many factors that can affect how a mattress feels and performs. I would have a difficult time imagining anyone needing more than 12" of a high quality foam though but depending on the design it may be a preference but the thicknes of a mattress isn't nearly as important as whether it matches your specific needs and preferences in terms of PPP (Posture and alignment, Pressure relief, and Personal prefeferences).


6) Do you happen to have a source to verify the above findings?

You could use a pressure converter such as this one here

7) If what is mentioned in the 2nd quote stands, then if we knew the net weight of the mattress (approximately) we would be able to calculate density. Is it really that simple? Or is it another made up story to confuse consumers?


A mattress usually uses many different types of foam or materials so you would need to know the thickness and dimensions of each layer and it's weight to calculate its density. If you did the calculation for the whole mattress it would be meaningless because it wouldn't tell you the density/quality of any individual layer unless there was only a single layer of material in the mattress (say a single 6" core). The density of latex is more of a "comfort spec" because softness and firmness with latex varies by density (as well as a few other factors) and it has little to do with the quality of the latex while with polyfoam and memory foam density is a quality spec and is an important factor in durability but has little to do with firmness or softness.

7a) Could the same be applied to a polyfoam mattress?


Again ... only if there was only a single layer of foam in the mattress.

7b) Could the same be applied to a single layer?


Density is only meaningful with single layers of polyfoam or memory foam.


Phoenix
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