I have been wanting to upgrade my couch cushions for quite some time, and what better time to do it than when I’m on a latex kick… Over time they’ve just lost their spring and I almost feel like I’m sitting on the floor now!
So I was thinking Dunlop in 35-40 ILD. Below is a picture of the inside of one cushion. It’s a 6" block of generic foam, with some thick (maybe 1") cotton or synthetic wool (not sure) batting glued to either side of the foam.
So some questions:
Where can one buy Dunlop in custom sizes?
Where to get the wool/cotton batting?
What kind of glue is used to attach the batting to the foam?
[quote]1. Where can one buy Dunlop in custom sizes?
2. Where to get the wool/cotton batting?
3. What kind of glue is used to attach the batting to the foam?[/quote]
While furniture isn’t an area that I normally do much research into, you may be able to find the supplies that you need at a local upholstery or foam store including upholstery glue although they may not carry Dunlop latex.
There are also some online sources in the component post here that would sell the supplies that you need. I know that Foamorder sells Dunlop latex for couch cushions.
It also includes some sources for cotton and wool batting along with Dacron batting (which would be more commonly used for couch cushions). The woolen mills that are listed in post #3 here would be able to supply you with wool batting as well.
OK thanks for the pointers. I found a source that seems fairly reasonably priced. So the question becomes - what firmness? Obviously a couch needs to be firmer than a mattress for the same person because more weight is concentrated in a smaller area. My options are:
The problem I am trying to fix is that the current polyfoam has become too soft and I sink too far in. So I want firmness, without feeling like concrete.
Furniture cushions certainly aren’t my area of expertise but I can share a few pointers that may be helpful although I would suggest talking to someone that is experienced with using latex as a couch seating cushion.
Polyurethane seating cushions are usually in an IFD range (IFD is basically the same as ILD) that ranges from about 25 IFD to about 45 IFD. 25 - 3o would be the most common for sofa cushions that are about 4" - 6" thick while 30 - 36 would be for firmer cushions and 36 - 45 would typically be used for thinner seat cushions to prevent them from bottoming out. In addition to the IFD … the compression modulus and the thickness of the cushion will both affect how soft or firm it feels and how likely it is to bottom out. There are a couple of good articles about seat cushions here and here.
All of this applies to polyurethane where the IFD is tested on samples that are 4" thick using a 50 sq in round compressor plate that is used to compress the 4" sample by 25% or 1".
The ILD of latex is tested in a similar way except the sample thickness is 6" instead or 4" so the material would be rated by the amount of force it takes for the same size compressor plate to compress the 6" core by 25% which in this case would be 1.5". Because the rating comes from a deeper impression which would require more force than compressing the same material by only 1" … the ILD ratings for latex would typically be firmer than an equivalent IFD rating for polyfoam so the 25% ILD for latex that was rated at say 36 ILD may closer to about 30 ILD for polyfoam. There is more information about the effect of sample thickness on firmness ratings in section 4.3 here.
So taking into account the effect of the different firmness ratings and the effect of thickness on testing the main thing left to consider is the effect of the compression modulus on the firmness and “ride” of a foam material. Since latex has a higher compression modulus than polyfoam (conventional polyfoam is typically about 2 and HR polyfoam is typically about 2.5 and Talalay is typically from about 2.5 to 3 and Dunlop is typically about 4) … I would modify the ILD of the latex slightly downwards to take the higher compression modulus into account.
This means that if you were planning to use a polyfoam cushion that was about 30 IFD that a rough comparison with latex would be about 36 ILD (about 20% higher) and then I would modify this downwards a bit to take into account the higher compression modulus of the latex.
Of course all of this is very rough because these types of comparisons aren’t necessarily accurate unless you are comparing the specifics of two materials but at least they will give you some reference points to start
Just a data point for others, ILDs in line with OP/Phoenix, except using HR Polyfoam (not Latex)…6’2" 230 lbs, tried 2.5" of 30 ILD HR Polyfoam over 2.5" of 40 ILD, and not supportive enough. Then tried 2.5" of 40 ILD over 2.5" of 50 ILD and too supportive/firm. Will now experiment with combinations of 34/40/44. Trying to avoid Dacron since also used as part of base layer of camper van mattress but might try thin layer of memory foam on top.
Over time they’ve just lost their spring and I almost feel like I’m sitting on the floor now!
