Other Equipment

foam deterioration


A friend of mine had some old Shure microphones that had been discontinued, and they came in a case with foam inserts to protect the mic. He hadn't used them in a while and when we pulled them out to record the foam had deteriorated and gotten all over the inside of the mic.

I have also had the foam on some old pair of headphones deteriorate. It makes me worry because I have my sennheiser 421 in a similar case, with foam insert, and my shure super 55 microphone has foam inside the grill. Does anyone know what causes the foam to deteriorate, how long it takes to happen, and what are my options for preventing it or replacing it in the microphone?


You can buy replacement foam from quality mic shop, this is a common problem with old mics.


I had this happen to my Roc Jet. I'm told foam just breaks down over time. When I bought it the guitar, it came in a super heavy duty flight case that was lined and fully supported my foam. It was pretty old when I got it but not long after I noticed the foam had started to break down and go sticky and gooey. It had stuck to parts of the body and I couldn't get it off. I got most of it off in the end with Mister sheen but couldn't completely remove it.

Having no alternative I stripped the case of all the old foam and re-lined it with new foam that is supposed to last much longer but as a bit of insurance I have covered the foam with velvet so none of the foam is in direct contact with the guitar now and it looks great as well.

I had another old flight case that was lined with foam that has also broken down since. After the 1st one, I had put the guitar in this case in a big cotton sock that I made from an old bed sheet so that it wasn't in direct contact, just in case. It worked fine. I have since relined that case that same way as the 1st.


Yup, that soft foam rubber rots. I don't know why, but it does. The sad thing is that it's in quite a few products. I doubt that anyone knew what it would do when they first started using it. It seemed like a wonderful thing when it came out. I'll bet that nobody expected binding to rot, either. replace it ASAP if possible. Like others have said, avoid direct contact as it's crumbly and sticky---I think it's an oil based product.


Case foam isn't hart to replace. If headphones are brand name, you can usually get replacement foam. Sennheiser has replacement foam for the 414's that doesn't seem to deteriorate, although it's still that ugly yellow. As for the stuff inside of mics, sometimes you can get a replacement, somtimes you have to improvise. I got some generic headphone replacement foam at Radio Shack and used it to replace the foam in a couple of EV 635A's and a 666. The earlier Shures had cloth instead of foam, usually dark blue but sometimes red. I thought that looked good, but it's harder to glue it in and make it look right than iiit is to use foam. You should fix the mic cases ASAP though so you don't get all of that powder and residue in your capsules.


You won't be getting foam at Radio Shack anymore, or much of anything else. I still use my 414s since I replaced the foam. The white ones had blue foam that wasn't as bad as the yellow. On cheaper headphones, it's easier to just buy new ones.

Lots of old EV and Shure mics used foam in their mics as a pop filter. A piece of cloth may work in place of it if it's an open weave.


Ozone deteriorates the foam. Present in the atmosphere. Nothing we can do about it.


I repair lots if pedals for a couple of music shops and if I get an old MXR pedal in, I know it's likely filled with disgusting crumbly foam that needs to be scooped out! It is nasty!


Shure sent me FREE replacement foam for my then 25+ year old PE86L that was long out of production. My opinion of Shure is very high.


Radio Shack is still around, they just closed a bunch of stores, but not all. For mics, find headset foam that's the right diameter. It's not hard to find if you get off your butt and look.


Our local Radio Shacks all closed up. They were only carrying cellphones and earbuds anyhow. Luckily, I have a good electronic parts house in town.



You'll find sizes to fit a lot of popular mics. Be aware that pillow and case foam is not the same a acoustic foam. You need foam with open cells that won't filter out sound. That's earphone foam is a good choice. For old Unidyne ll tyoe Shures, you need a sheet of 1/8" acoustic foam and a little super glue.


Sorry, I can't type and talk on the phone at the same time.


High quality memory foam, takes eons to deteriorate. I would use that to replace any other type of foam. You might want to contact Tempurpedic and see if they will sell you some since theirs is by far the best. They sent me a big chunk that I use under my Jaguar pickups.


I don't think memory foam is acoustically transparent enough to use inside a mic. Whatever Sennheiser uses for the replacement 414 pads is extremely long-lasting. I bought an extra set 20 years ago, expecting them to wear out like the originals. I doubt that I'll live long enough to need that other set.


Foam breaks down on its own and any contact with petroleum based adhesives - even fumes - greatly accelerate this process.


BZ, I've got to ask. Aside from carpentry, what do you use an EV635 for? I've worked in broadcast as well as on stage so I'm quite familiar with EV gear. I just wondered what use you found for an omni mic.
By the way, my Dad worked for EV back in the late '40s, and We lived 15 miles from the Buchannan plant. I'm still looking for a South Bend badged EV mic---I don't even care if it works.

You're right about the Tempurpedic foam. It's closed cell and not porous at all. It'd be OK for storing mikes, but not for use inside of them.

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