Latex - Maximum/Highest Firmness or Indentation Load Deflection (ILD) for Dunlop

I recently bought a 7" firm single layer dunlop latex mattress (32-36 ILD / Density: 90) from a TMU member company - the firmest they sell. Great price, certified organic materials, great service but my back is unhappy, Iā€™m waking up with muscle soreness. This manufacturer tells me I should have purchased something softer from them adding 32-36 IDL is the highest achievable with the dunlop process.

I am very interested in staying with latex and believe Iā€™d do best in something akin to 1.8 high density polyurethane foam or the firmness of a crib mattress.

I found another TMU participating manufacturer who lists a 63 ILD for dunlop mattresses and tells me in the future they will carry even higher ILD dunlop. I asked for an explanation of how this is achievable and the response was ā€œour dunlop latex is from Vietnam and is most likely a different vendor than the previous company you may have been talking toā€ and ā€œI am not sure what further information you are wanting in regards to our dunlopā€. And yet add their 7" two layer 3" (32 ILD) and 3" (63 IDL) which Iā€™m considering buying ā€œmightā€ feel firmer than what Iā€™m currently sleeping on - I donā€™t want to waste anyoneā€™s time or valuable resources so I need a more certain response before proceeding.

Experts, what is the maximum/highest firmness for dunlop latex? Is what Iā€™m looking for possible to achieve with latex?

Thank you in advance for your time.

Hi aldaarias,

Welcome to the Mattress Forum! :slight_smile:

Iā€™m sorry youā€™re ā€œwaking up soreā€ with your new mattress. While itā€™s not possible for me to diagnose soreness issues via an online forum, there is some information about the many different symptoms that people may experience on a mattress and some of the most common causes behind them in post #2 here that may be helpful. Pressure points and general soreness tend to be a surface comfort issue (usually requiring thicker/softer comfort materials), which could be why you received the recommendation that you did about choosing something slightly softer. Many low back issues - ones which can take most of the day to overcome - tend to be alignment related, which quite often points toward inadequate deep support. The mattress you have is generally regarded as quite firm, so this may not necessarily be the case, but you also donā€™t list your sleeping style nor BMI, so itā€™s possible you may personally prefer even firmer/thicker materials.

As far as 32-36 ILD being the ā€œhighest achievableā€ via the Dunlop process, that wouldnā€™t be correct. While I wasnā€™t part of your conversation, my guess would be that either the manufacturer was referencing the firmest Dunlop that they offer, or the firmest Dunlop that their supplier provides them.

Density of polyfoam isnā€™t indicative of firmness, and polyfoam compresses differently and doesnā€™t ā€œfirm up as fastā€ (has a lower compression modulus generally) than latex. Dunlop will tend to be a bit softer during its initial compression, then firm up as more weight is applied. But it will be more point elastic than a typical base polyfoam.

Dunlop latex is more accurately compared via density as opposed to ILD. While ILD estimates can certainly give you a good idea of the comfort, ILDs are ranges, and the ranges are larger (generally+/-4 or so) for Dunlop versus Talalay (generally +/- 2 or so). There are also variations in how the ILD is calculated (thickness of the piece tested, the percentage of compression, hold time, and so on), so unless a specific piece of Dunlop foam was measured, itā€™s usually more accurate to compare Dunlop via density.

With that being said, if a company has a piece of Dunlop that they say is rated at 63 ILD, this most certainly would be a very firm piece of Dunlop, and could likely be something tested at a 40% compression in the 95-100 kg/M3 range for density.

Different Dunlop pourers in different parts of the world will manufacture their latex to suit those specific areas, and in the case of Vietnam (Lien A, for example) they produce 95+ kg/M3 density Dunlop that, depending upon the method of measurement, would be well over a 50 ILD. Firmer mattresses are more common in Asia in the east and southeast regions.

Iā€™m not exactly sure what youā€™re desiring for a more ā€œcertain responseā€ about. If you had two 3" layers of Dunlop at 32 and 63 ILD, and if the Dunlop was measured the same and of the same style (natural, blended or synthetic) as what you currently have, this would have firmer ā€œdeep supportā€ than your current mattress. But I unfortunately canā€™t predict if this is the solution to your needs nor what you may find preferable.

I donā€™t know that there is a ā€œmaximumā€ Dunlop density achievable, but Iā€™m sure the different latex foam pourers have found different densities they can consistently produce at the firmest levels. There are manufacturers producing Dunlop over 100 kg/M3 for use in mattresses, which would be quite firm, and there are ones producing even firmer latex for the equine industry! But in general, in North America, the ā€œfirmestā€ Dunlop that is ā€œcommonlyā€ offered is in the 90-95 range.

Phoenix

Phoenix, thank you so very much for your speedy and detailed response, so appreciated.

Iā€™ll likely respond with more details later as my time parenting a toddler allows.

To respond to some mayor points here. In most mattresses I feel like the ā€œtoo softā€ in the back alignment diagram in the post you kindly included. I previously had a cheap and too soft coil and poly foam mattress from Ikea and I believe thatā€™s where my issues stem from. My husband and I are petite people; I am 5ā€™3" tall, 130 lbs and a BMI of 23.0, my husband is 5ā€™6", 146 lbs with a BMI of 23.6. I have a herniated disk at L1/S1, so yes lower back problem indeed. We definitively prefer firm sleeping surfaces and sleep in all positions.

The first seller states on their site their GOLS organic Dunlop is sourced from ARPICO in Sri Lanka. The second seller states their 100% natural latex is sourced from Lien A in Vietnam. The first seller says their layer has 90 density. The second seller says the layers Iā€™m considering have a 5.9 and 6.0 density respectively. How can I use these numbers for an apples to apples comparison of the higher firmness Iā€™m looking for? Could the Lien A latex contain additives to get to the higher ILD?

Maybe a zoned core would be best for us. Would you know which TMU sellers stock GOLS organic Dunlop zoned cores in the US?

Thanks again.

Hi aldaarias,

Youā€™re welcome!

Iā€™m sorry to learn about your low back issues. :frowning: But it seems that you certainly prefer a firmer sleeping surface, as what you have right now is generally considered quite firm.

As I commented previously, the density will be the more reliable comparison between two Dunlop layers, and the ILD isnā€™t quite as accurate unless a specific core of foam has been tested. Overall, the hardness of the latex can be influenced by such factors as the density, type and mix of the latex, fillers, method of vulcanization, and the size and distribution of the pin-holes.

Most Dunlop manufacturers test ILD using a 6" core. The ILD rating is then taken at either a 25% compression or at a 40% compression. The most common measurement for cores in North America is 25%. If the core is 6" then 25% would be 1.5", and 40% compression would be 2.4". So the 40% ILD number would be higher than the 25% ILD number for the same latex. With Dunlop, some ILDs are estimated via formulas the manufactures have set up. Others are actual measurements.

In some charts I have for Arpico (Iā€™m not sure of the actual blend of Dunlop), they list ā€œpossibleā€ ILDs for their 85 (+/-5) kg/M3 in the 31-36 ILD range (at 40% compression). At 95 (+/- 5) kg/M3, they list the possible ILD range as 39-45 ILD.

The numbers you were given for Lien A are in lb/ft3, so the 6 would translate roughly to a 95 kg/M3 density. This is sometimes termed an XX Firm, and in the attached chart you can see it rates as an approximate 46 ILD, but Iā€™m not sure of the compression of this (25% or 40%).

Thereā€™s another chart I have (see attached) of common Dunlop ratings from around the world, and in this chart (at 40% compression), there is a representation of Dunlop in the 95-100 kg/M3 range listed with an approximate ILD of 59-66, of which the 63 ILD you are being quoted would fall right in the middle.

All of this goes to show you that ILDs are not quite as clear-cut a manner to compare Dunlop latex, and while the different piece of latex youā€™re considering should be firmer than your current product, I donā€™t think the difference will be as dramatic as the ILDs have been represented to you, for the reasons in ILD representation as Iā€™ve described.

As for site members who sell zoned latex cores, you may wish to investigate:
Arizona Premium
FloBeds has a very unique zoned system
SleepEZ may be able to procure a zoned Dunlop core for you, but youā€™d have to phone them

Most people that are looking for an ā€œorganicā€ mattress or materials are usually concerned more with ā€œsafetyā€ than whether the materials have an actual organic certification and they usually arenā€™t aware that an organic certification isnā€™t the same thing as a safety certification. There is more information about the three different levels of organic certifications in post #2 here and some of the benefits of an organic certification in post #3 here and there is more about the different types of organic and safety certifications such as Oeko-tex, Eco-Institut, Greenguard Gold, C2C, and CertiPUR-US in post #2 here and more about some of the differences between organic and safety certifications in post #2 here and there are also some comments in post #42 here that can help you decide whether an organic certification is important to you for environmental, social, or personal reasons or whether a ā€œsafetyā€ certification is enough.

Phoenix