Hammocking in new latex mattress
|
My wife and I have a new Gardner latex mattress, medium firmness. They're pretty close-lipped about construction and won't talk ILDs, but they do claim all-Talalay construction - though they spell it Telelay; inside the mattress casing their medium and firm are both 6" of a firmer latex under a 3" comfort layer of less firm latex. (Their plush and ultra plush have a 4" comfort layer and cost a little more.) I'm a back-and-side sleeper. This mattress was supremely comfortable in the shop on both back and side over about fifteen minutes - no pressure points, cushy support; the firm mattress was a bit unyielding under shoulder and hip and I was a little worried about pressure points. But last night I slept on my back and woke feeling a bit like I was in a hammock. Particularly when I went to roll onto my side and found a bit of pressure against the bottom of my rib cage and the top of my thigh. As if they were on the edges of a hole that my butt had formed during the night. I had to get up an hour early; the mattress was quite warm and shaped for back sleeping, and I couldn't get comfortable in any other position (and felt a little hammocky in that position). A week or so ago I pulled a muscle in my back at the gym, and now have a little occasional pain in a narrow stripe from the left of my spine out towards the left, and when I was trying to get comfortable on my side I felt pain there. My pelvis was trying to tip up because my legs were out of the hole my hip was in. I've been mostly sleeping on my side - actually on the front part of my side, so my weight isn't so much on my butt as on the fronts of my thighs, and I get better support without the hammocking. I've read on this site in a few places that latex often sinks in a little bit after a few hours. I'm wondering if anyone can give details, because I only have a week in which to decide what to do. I think my options at this point only really include keeping this mattress and swapping it in for the firmer version - but will that be worse for me? What's behind the hammocking? Maybe I should just lose weight, but that's not a good short-term solution. My wife loves this mattress. What should we do? |
Re: Hammocking in new latex mattress
|
cloud9 wrote: Talalay latex is an "active" foam. It wants to return to its original shape while you are lying on it and it will exert force against your body to do so. The higher the ILD the more pressure it exerts. Haysdb, I'm sure you know what ILD is, but for the benefit of those who don't, it's the amount of force required to compress the foam 1". It stands to reason that if 44ILD foam needs 44 lbs of pressure to compress it 1" that same degree of pressure is being exerted back against your body by the latex. An innerspring mattress may just feel hard but it does not exert force against your body. Don't springs exert pressure as they try to return to their original shape? Wouldn't that be considered an active material? |
Re: Hammocking in new latex mattress
|
cloud9 wrote: Talalay latex is an "active" foam. It wants to return to its original shape while you are lying on it and it will exert force against your body to do so. The higher the ILD the more pressure it exerts. Haysdb, I'm sure you know what ILD is, but for the benefit of those who don't, it's the amount of force required to compress the foam 1". It stands to reason that if 44ILD foam needs 44 lbs of pressure to compress it 1" that same degree of pressure is being exerted back against your body by the latex. An innerspring mattress may just feel hard but it does not exert force against your body. You just feel "pressure points" where hips and shoulders press more deeply against it. Latex, oddly, does not produce pressure points because there is nothing rigid inside. It always feels squishy, which gives you a false sense that it's comfortable when it's really working against you. If you don't suffer from any kind of inflamatory condition like arthritis you may never notice this. If you do, after a few hours on a firm latex mattress even the floor seems more comfortable. It is not precisely accurate to say that ILD (aka IFD) is "push back force". The ILD we refer to is the force required to compress a foam 25%. The standard sample is 4" thick, so this is indeed 1", but more generally it's referred to as the 25% ILD. There is also a 65% ILD that's not talked about as much. According to the Polyurethane Foam Association INDENTATION FORCE DEFLECTION (IFD) -- A measure of the load bearing capacity of flexible polyurethane foam. IFD is generally measured as the force (in pounds) required to compress a 50 square inch circular indentor foot into a four inch thick sample, typically 15 inches square or larger, to a stated percentage of the sample's initial height. Common IFD values are generated at 25 and 65 percent of initial height. Here is a link to a Foamex document GLOSSARY OF FLEXIBLE POLYURETHANE FOAM PHYSICAL PROPERTY TERMS It's also not accurate to say that latex pushes back harder than a coil unit, or the ground. Or that a coil unit doesn't push back at all or exert any force on your body. |
Re: Hammocking in new latex mattress
|
haysdb wrote: It's also not accurate to say that ... a coil unit doesn't push back at all or exert any force on your body. Agreed. That's actually exactly what a coil spring does do. If your weight pushes the spring down, the spring is obviously going to push back. A "false sense that it's comfortable" would be impossible wouldn't it as comfort is subjective? Perhaps a false sense of conformity? I was no expert in physics but the logic seems flawed on the "44 lbs" argument also. hayesdb would be better suited to further go into that one. hehe If you put a golf ball on the bed and pushed down on it, when you let go that golf ball would fly if there was actually 44 lbs of pressure pushing back. I don't have a golf ball so try it out and let me know what happens. lol The jury is still out on whether Im with you on your hatred of latex cloud9 (I may be) but just trying to be accurate here. :) |
Re: Pushback force
|
We're wondering far afield here, but... Here is the most complete description of IFD / ILD that I have come across. http://www.pfa.org/jifsg/jifsgs4.html Speaking of the golf ball, if you press a golf ball into a chunk of ILD 44 latex and release it quickly, it will indeed be launched into the air. This is almost literally the ball rebound test and is a measure of resilience, which is independent of IFD. Here are a few passages from the above document: 4.2.1 In this publication, The Joint Industry Committee has purposely avoided using the word "comfort" directly associated with IFD or IFD properties. Suffice to say, IFD is a part of the comfort equation, but IFD is not always related directly to comfort. For example, one cannot say that a 25% IFD of 26 lbs/50 in2 always produces comfort, while a 25% IFD of 40 lbs/50 in2 does not produce a comfortable seat. Comfort is not directly related to the magnitude of the IFD number alone. Here is one I find especially interesting. 4.3 IFD varies significantly with foam thickness. On the exact same foam, the IFD increases as the thickness increases Latex International tests every core, but a latex core is either 5.6" or 6" thick. The 25% IFD will be higher on a 6" thick piece of foam than it is on a 4" piece of foam. Do they adjust for this? Something else to throw into the discussion is "support factor" which is the ratio of 25% ILD to 65% ILD. Two foams with identical 25% ILD's can differ significantly in how supportive they are. 4.6.3 Support factor can be related to comfort of furniture. Higher support factor foams of the same 25% IFD will provide more load bearing at higher deflection values. It has also been claimed that with higher support factor values, softer foams may be used in cushions. This document is actually rather interesting reading, at least for a nerd like me. It highlights very clearly that this 25% ILD number we are so find of is a really slippery thing. Two tests of the same foam with the same test equipment can produce different results! The ILD of foam from different parts of a bun can vary widely. ILD varies with temperature and humidity. This is why ILD is typically specified as a range.Sorry, back to your regularly scheduled programming... |
Re: Hammocking in new latex mattress
|
Well, we've swapped our mattress out with Gardner for the firm, which turns out to feel softer than the one in the store does (on our split foundation that came with the medium) but has none of the hammocking. I sink in just a tad at the hips, but not too much. It's very comfortable, and I can change position through the night and be instantly comfortable in the new position. (That said, I think I understand why Nature's Rest and some others go with zoned latex, the down side of which is of course that you can't rotate your mattress. Ours is rotatable, but I've gotten some contrary info on how often to rotate - "a few times per year," "you never have to rotate it," and "every couple of weeks for the first few months, then every 3-4 months" - rather confusing.) Just FYI. I do think the medium had sunk in about as far as it was going to after 5-15 minutes, and appeared to return to normal after 5-15 minutes, so that seems to be the behavior of the latex. And I'm still no wiser as to the construction of the latex mattress, ILD-wise. |
Re: Hammocking in new latex mattress
|
tcdonaghey wrote: Just FYI. I do think the medium had sunk in about as far as it was going to after 5-15 minutes, and appeared to return to normal after 5-15 minutes, so that seems to be the behavior of the latex. And I'm still no wiser as to the construction of the latex mattress, ILD-wise. If the mattress is doing anything other than returning to its original position immediately, then its something other than latex that you're dealing with. |
Re: Hammocking in new latex mattress
|
D3Fi wrote: If the mattress is doing anything other than returning to its original position immediately, then its something other than latex that you're dealing with. Definitely. Latex is about the most resilient material you will find in a mattress, second only to springs. Latex is a very "fast" foam, with no "memory." Latex should spring back to it's original shape immediately. |
Re: Hammocking in new latex mattress
|
Gardner does claim their latex mattress composition is 100% talalay (although in the store they call it "telelay") under the ticking. I get pretty much instantaneous return with the firm. Even after six hours in one position, on a hot night. Even with the medium I got instantaneous return if I didn't lay there long enough for the deep sinking effect to take hold, but at 5am on a hot night it was pressed in pretty good for long enough to be uncomfortable upon switching positions. (After fifteen minutes out of bed it looked perfectly flat, but what with the warmth in the mattress under where I'd been sleeping, it still felt a little softer there than on the cooler portions to either side.) I don't know as much about the physics of latex foam as I perhaps ought to to evaluate anybody's claims on the subject. Anybody wanna swing by Gardner and give a guess as to what they make their mattresses out of, is more than welcome. |
Re: Hammocking in new latex mattress
| Now that I have embraced the component mattress, it would drive me insane if I had a regular mattress and there was something not quite right about it. I've never even thought about it with my current mattress because until recently I never had any mattress-related issues. Ah, the good old days, when ignorance was pure bliss. |
Re: Hammocking in new latex mattress
| D3Fi, I wouldn't say I hate latex. I just don't think it's the be-all, end-all it's cracked up to be. Particularly Talalay latex, touted as superior to the older Dunlop process. I slept on a Dunlop latex bed for 20 years and in my opinion it's a much better sleep surface. The foam is much denser so it provides more support at softer ILDs. It is not prone to the hammocking sensation often described with softer Talalay. Because of the density it has bounce without the jiggly "jello" feel, and unlike Talalay it does not exert force against your body. It's nice and passive. I would be willing to bet that if all the people like myself who found it impossible to sleep on Talalay, tried Dunlop latex, they would have a much easier time of it. Sometimes the newer technology just doesn't live up to the hype. |