Custom cut HR36-130 foam mattress softening over night reducing deep sleep % after a few hours

Discussions General Mattresses Questions
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Hello All!

So excited to have stumbled across this forum and website. Have been struggling with sleep and mattresses for the last 6 months and have gotten into the technicalities myself without guidance. Just today I posted to reddit to try get some help and following that stumbled upon this beauty you guys have here. Reading the guides and articles I feel I am in similar minded intelligent technical company, and am excited to share my experience and draw on yours.

So, chasing some input here.

I’ve grown up and spent most of my 20s (28 now) sleeping on a 10cm simple foam mattress without any issues, up till about 6 months ago. I’ve always been a great sleeper, no back pain or tiredness issues. In fact I started using SleepAsAndroid to track my sleep about 18 months ago and I was averaging 70% deep sleep and 7-8 hours a night, waking up fresh. I optimise sleep with blue light filters, dim orange room lights, evening cardio, etc etc. I start sleeping either on my belly or side, but my body always ends up corrected on my back within an hour or so, always on my back upon waking. I am male, 175cm, 75kg, no relevant medical issues.

About 6 months ago, my deep sleep % gradually started reducing, I started waking up tired, started noticing im tossing and turning a lot in the night, and waking up. At the lowest, the deep sleep % got to 20-30%, essentially getting a half to a third or less than the sleep I normally did. I realised the foam had deteriorated in the centre so that sleeping on it there was not much support at all, feeling like sleeping on a hard surface, instead of the soft surface with good support prior.

To remedy this I went out and got an Ikea Malvik medium firm foam 14cm mattress (the best non memory non latex they have). This only marginally improved sleep, as overall deep sleep % increased to ~40%, but I found that the area of the mattress slept on overnight had slight compressed and become softer by the morning, more so around the area of lower back and buttocks. I was waking up with pain to my lower back. I do not have a history of such, ever. I determined that this was due to the Ikea mattress being made of a lower quality, less-resiliant foam, so that it would not hold its firmness under compression overnight resulting in a gradual sinking of the lower back into the bed overnight causing shifting away from neutral spinal position and thus tossing and turning overnight and therefore less deep sleep.

To remedy this, I looked up the manufacturer of the original foam mattress I had (Joyce Foams Australia), consulted their [technical specification brochure], spoke to a few foam sellers in the area (Perth, Western Australia), and decided to have a 15cm slab of their highest quality foam cut to queen size. I chose the highest grade as:

  • this gives a lifetime warranty
  • gives the highest resilience factor (50% - a measure of the springiness, or bounce. Lower quality foams for eg guest or child use is 20-30%)
  • gives the highest comfort / indent factor (2.2 - the ratio of the force required to compress the foam to 65% and 25% of the original height. I.e. A higher factor means soft initial feel with good low down support)
  • gives the highest nominal density (36kg/m^3 - more material tends to apparently mean less breakdown and overall better foam)
    I chose a hardness rating of 130N as when tested to Australian Standard AS2282. This is a standard hardness for mattresses and considered medium, and was advised to select this by a few different foam specialists. So the foam I chose was the HR36-130CM5. After seeing and feeling it, and looking at the numbers, I was confident it would provide good support and a soft initial feel.
    ADMIN NOTE:Removed 404 page link | Archived Footprint: joycecomau.melbourneitwebsites.com/files/joyce_technical_brochure_2015.pdf

The foam does, in fact, provide a good soft surface feel, and provides good support, upon laying on it I feel well supported in my lumbar spine, dont feel pressure areas on my skin and feel my spine is in a neutral position. Unfortunately, after a good 8-9 hour sleep, again, the area of foam slept on, feels softer than the surrounding foam, more so in the area of the lower back and buttocks. This seems to be only after a sleep, and the feel returns to consistent throughout after a few hours of non use. I feel what is happening is after a few hours of use the foam under highest pressure gradually becomes softer, causing the lower back and buttocks to sink more causing loss of spinal neutrality. This is similar to what was happening with the Ikea mattress, however not as bad. To clarify, following sleep, in the morning, there is no indent as such, however the foam around the area where hips and buttocks were overnight is softer, and so the body sinks in further than it did before sleep commencement when the same area was as hard/soft/compressible as any other area of the foam.

The sleep analysis almost confirms this theory, as the first 4 hours of sleep are good, with approx 60% deep sleep, and good cycling through REM and brief light sleep. However, after the first 4, there is a lot more movement and a lot more light sleep, I assume as the spine is losing neutrality and the body attempting to correct through movement.

I’m at a loss as to whether this overnight loss of support is normal in mattresses and expected (perhaps my understanding of neutral spinal position is incorrect?) , or indeed normal for foam. And also how to correct this. One idea I have is perhaps to have the foam height cut down to 10cm, so that any overnight loss of support is reduced.

I’m open to ideas. I’m open to criticism of my analysis, conclusions and methodology. I’m hesitant to simply go out and buy another mattress on suggestion prior to understanding the technicalities of my previous two failures.

Any help is greatly appreciated. Just chasing a good nights sleep!

Cheers

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Hi thereisriceandcurry,

[quote]I’m open to ideas. I’m open to criticism of my analysis, conclusions and methodology. I’m hesitant to simply go out and buy another mattress on suggestion prior to understanding the technicalities of my previous two failures.

Any help is greatly appreciated. Just chasing a good nights sleep![/quote]

My first comments before I get to a few additional comments are the most important …

While I can certainly help with “how” to choose … it’s not possible to make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort” or PPP or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).

While knowing the specs that can affect the quality and durability of the layers and components in a mattress is always important … unless you have a great deal of knowledge and experience with different types of mattress materials and components and their specs and different layering combinations and mattress designs and how they combine together and can translate them into your own “real life” experience that can be unique to you (which would generally be a very small percentage of people) … I would tend to avoid using complex specs to try and predict how a mattress will feel or perform for you. When you try and choose a mattress based on complex combinations of specs that you may not fully understand or only based on specs for a single layer or component that may not be as relevant or meaningful as you believe it is then the most common outcome is “information overload” and “paralysis by analysis”. Even the best mattress designers in the industry are often surprised at what a mattress they design “should have felt like” based on the specs when they design it and what it “actually feels like” when they test out their new design.

On to some more general comments that may be helpful.

First of all I will need to “translate” some of the specifications you are using so that we are using the same terminology since this is a North American forum and the terms that are used for different specifications are different than the ones you are using.

Density here is measured in lb/ft3 so you can translate this into kg/m3 using the density converter here. Density is the single biggest factor that affects the durability of polyfoam (although firmness also affects durability) but it has little connection to firmness and is only loosely connected to resiliency (springiness). Any density of foam can be made in a wide range of firmness levels and can be formulated to be more or less resilient (although higher density foams are often more resilient than lower density foams).

Firmness is generally measured here using ILD (Indentation Load Deflection) or IFD (Indentation Force Deflection) @ 25% compression (both are functionally the same) instead of Newtons @ 25% compression and you can convert one to the other using the force converter here.

What you are calling comfort factor or indent factor is more commonly called compression modulus (also called sag factor). This is the rate that a foam material becomes firmer as you compress it more deeply so it can be softer with initial compression and then firmer with deeper compression. Lower quality/density foams will be under 2 while higher quality/density foams can be closer to 2.5 - 3. Talalay latex will be “about” 3 and Dunlop latex can be 4 or higher.

The “translation” for the foam you purchased would be 2.25 lbs/ft3 and 29 IFD and the compression modulus and resilience would be the numbers you mentioned.

Next it would be helpful to clarify the difference between the different types of support and their relationship to pressure relief because both of these can affect the quality of your sleep.

“Support” is often misunderstood because the goal of a “supportive” mattress is to keep the spine and joints in good alignment and this requires the type of contouring support that allows some parts of the body to sink in more (softer) and some parts of the body to sink in less (firmer) and this will vary on an individual basis. 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 also be helpful in clarifying the difference between “support/alignment” and “comfort/pressure relief” and “feel” and how they interact together.

A mattress that doesn’t provide enough pressure relief (the top layers or section of the mattress is too firm) can result in pressure points and tossing and turning and lower the quality of your sleep. A mattress that doesn’t keep your spine and joints in good alignment can also result in lower back discomfort or pain and can lower the quality of your sleep as well. The goal is always to find the right balance between comfort/pressure relief and support/alignment that is suitable for a particular person’s body type and sleeping style. It’s also very common to use multiple layers to accomplish this so that the properties of a mattress and how it responds aren’t limited to the properties of a single foam layer (the top can be softer and can be customized for softness and pressure relief and the deeper layers can be firmer and can be customized to provide better support). In other words the response curve of a mattress can be changed more effectively using multiple layers of foam than it can by using a single layer where your only option is to choose different types of foam with different properties.

As long as the foam density is “durable enough” for your body type then the other specifications are more about the “comfort specs” or “performance specs” of a mattress and which type of foam or which set of specifications may be more suitable for any particular person can vary widely between different people. A mattress (or foam layer) that works “perfectly” for one person may be completely unsuitable for someone else with a different body type, sleeping style, or preferences to sleep on. In other words using higher quality/density foams doesn’t necessarily translate into a better sleeping experience.

I would also keep in mind that the resilience of a foam doesn’t necessarily “translate” into good sleep quality although it can certainly affect the ease of movement and changing positions on a mattress. Some people sleep very well on memory foam and it has a very low resilience and very high hysteresis (the ability to absorb energy which is the opposite of resilience).

Finally some comments about your choice

ILD/IFD is only one of several specs that makes one material feel softer or firmer than another (see post #4 here).

Thickness can also make a difference in the properties and feel of a material as well because a thicker foam layer will feel and perform differently than a thinner layer of the same material. There is more about the effect of thickness in post #14 here.

There are also several reasons that could account for the change in your sleeping experience.

One of them is changes in your own specific needs and preferences over time.

Another is changes in the mattress (which is quite likely)

Another is any changes in the support system you are using under the mattress. If your support system (a steel or wooden bedframe and a foundation or a platform bed) is sagging then this will also affect the mattress and could be part of the cause of your sleeping experience as well. You can test your support system to make sure that it’s not the cause of your issues by putting your mattress on the floor to see if it makes any difference.

Another is any changes in what you are using on top of the foam layer (the mattress cover or any mattress pads, mattress protectors, or toppers you may be using) all of which will have an effect on the feel and performance properties of a mattress to different degrees.

Assuming that the primary cause for your experience is the mattress (it could be a combination of causes) … then it would make sense to try and find out the specifications of the foam layer you were using (density, ILD/IFD, compression modulus) and try and “match” it as closely as possible using the same thickness of the same material. Every difference between the specs of the foam layer you purchased and your original foam layer that affects how it feels and performs could have a beneficial effect, a negative effect, or a neutral effect on your sleeping experience but the only way to know whether any specific foam layers will work well for you will be based on your own personal experience.

Since thinner mattresses will “act” firmer … it would also make sense to start by using the same thickness that you were successfully using before.

It’s normal for any foam material to get softer over the course of the night with continuous compression and then recover it’s firmness during the day. This is called “foam ceep”. Using a thinner layer may also reduce the effect of foam softening over the course of the night that puts you out of alignment because a thinner layer will get firmer faster than a thicker layer.

While I realize that this won’t help you decide on the specific type of foam that has the best chance of success (unless you are able to duplicate the original mattress that worked best for you) … at least it may help you realize that the “comfort” or “performance” specs that work best for you may not necessarily be the “best” specs available and if you aren’t able to find out the specs of your original mattress it may take some trial and error to find the type and specifications of foam that is closest to it or that works best for you.

Phoenix