deskthority

Hey guys,

I've been working on bolt modding a 1985 British-made IBM Model M, yet am somewhat worried about two things:

- There is a black, rubbery sheet which which lies between the flippers of the Model M's keys and the transparent membrane. I guess it's what allows the membrane to register key presses. The reason why I am worried is that it has a strong smell that is reminiscent of oil and the type of ink that is often used to print newspapers. Does anyone know what causes this smell, and whether it is toxic?

- I've been drilling holes in the barrel plate. My wife is worried that that, too, might be toxic though. I think this is rather unlikely (I do realise inhaling dust is never good for your health) but the plastic does look a bit swirly, which could, potentially, suggest that there is an admixture of some kind. Does anyone know if pure ABS was used, or, perhaps, something else?

Many thanks in advance!

I'm no Model M expert, but I think I know what smell you are talking about. It seems all old Models M and F smell strong. The Models F I've opened, especially the F122s, smell like aircraft hangars. Just all musty and oily. I haven't heard anything about any of the materials used being particularly toxic.

A picture would certainly be helpful. I doubt it's much of a problem, but visuals would definitely help determine what's up with it.

Thank you for your replies!

I'll take pics later today (after our Christmas breakfast ). I don't think there's a lot to see, though. There's nothing odd to the rubber sheet beyond it smelling bad.

A few years ago, I bought another Model M with the intention of bolt modding it. That one smelled even worse (it was the same smell, though, just stronger). At the time, I thought it'd been used in a printer's shop or garage and that the sheet had just 'absorbed' the fumes - but it appears the smell is from the sheet itself.

Cattus_D wrote: ↑

25 Dec 2021, 09:39

Thank you for your replies!

I'll take pics later today (after our Christmas breakfast ). I don't think there's a lot to see, though. There's nothing odd to the rubber sheet beyond it smelling bad.

A few years ago, I bought another Model M with the intention of bolt modding it. That one smelled even worse (it was the same smell, though, just stronger). At the time, I thought it'd been used in a printer's shop or garage and that the sheet had just 'absorbed' the fumes - but it appears the smell is from the sheet itself.

I hope you have a lovely Christmas! As for the M, I wouldn't worry about it - just wear a painter's mask or something while you're working on it if you're not sure. I think it is fine though.

Thanks for the reply, Wazrach - and happy Christmas!

Here are the photographs that were requested. I've also sent an e-mail to Unicomp - perhaps they can shine a light on the odd smell coming from this old Model M.

The 'blanket' (that's what it's called) smells because it is made out of rubber (actual rubber, not plastic with tons of actually toxic plasticizer). The smell is the same as you get from bicycle tires and things like that and unless there's additional chemicals in there it should be harmless.

I just scrub the blanket with hot soapy water. Don't worry about it.
The barrel plate is very common ordinary plastic, nothing to worry about there, either.

If you are contacting Unicomp, they no longer use the old thick black rubber blanket but rather a thin white latex one. I think that it costs $10 and it is a good upgrade in my (and many other people's) opinion.

some people have allergies to rubber and chlorination is a way to chemically treat it to avoid that issue. i think it uses bleach so you probably already have all you need to do so.

Have experienced a similar smell from my oldest Model M - never gave it much thought, though.

Thank you for your replies, everyone! Good to know regular rubber was used (and ordinary plastic ).

I've been able to reduce the smell using first soda, then vinegar. The smell didn't entirely disappear, though. Currently trying what happens if I add a thin layer of water-based binder's glue. This is a trick I've used before with an old toy whose plastic was decomposing. The glue created a new, rubbery top layer that was dry to the touch (previously, the toy would get sticky due to the plasticiser leaking out). If I'm succesful, I will let you know.

Cattus_D wrote: ↑

25 Dec 2021, 20:54

Thank you for your replies, everyone! Good to know regular rubber was used (and ordinary plastic ).

I've been able to reduce the smell using first soda, then vinegar. The smell didn't entirely disappear, though. Currently trying what happens if I add a thin layer of water-based binder's glue. This is a trick I've used before with an old toy whose plastic was decomposing. The glue created a new, rubbery top layer that was dry to the touch (previously, the toy would get sticky due to the plasticiser leaking out). If I'm succesful, I will let you know.

As long as the sheet doesn't become inflexible.

<crinkle crinkle>

Those black mats can be well smelly. Had a really bad one in my M122. Took it out completely. But kept it in storage for the next guy who bought the board from me.

Unicomp's white replacements are much nicer. Haven't tried installing one however, so can't vouch for what effect it has o feel and sound in the keyboard. Just shared shipping and got to handle the part. They're silicone soft and scentless.

Thank you for the additional info about the silicone replacements from Unicomp, Muirium.

They do not appear in their webshop, but perhaps their customer service can help me out.

Using the PVAc-glue trick worked more-or-less as intended (no more rubber smell!), yet when I punched holes through the new top layer it'd produced (the glue filled most of the holes in the rubber sheet) some of the new top layer separated from the rubber, resulting in an irregular surface; I therefore think I'll simply replace the rubber sheet, whether with a silicon blanket from Unicomp or a similar sheet from another vendor.

Quite a lot of Unicomp's parts aren't listed in their store. Some people think that the crude nature of their web presence adds to their charm!

Since I have a few pieces of latex clothes that I chlorinated, the texture and color matched it. I think it's safe to say it's chlorinated latex.

Latex, you say?

Muirium wrote: ↑

01 Jan 2022, 15:16

Latex, you say?

Spoiler:

Well I could not blame them, latex was meant to be worn. You got to admit, they look kick ass.

Muirium wrote: ↑

01 Jan 2022, 15:16

Latex, you say?

Spoiler:

Buck Rogers? I remember watching that show when I was a kid.

Same. And some of it has stayed with me, ever since. Mostly the very best of the spandex bits, Colonel!

I've had a reply from Unicomp about the composition of the Model M's barrel frame. They tell me it contains teflon!

The barrel frame is unremarkable except that it is infused with teflon. The swirl [...] is common in injection moulded plastics (it is called Splay), but is perhaps more visible due to the teflon reflecting more light.

Cattus_D wrote: ↑

04 Jan 2022, 10:02

I've had a reply from Unicomp about the composition of the Model M's barrel frame. They tell me it contains teflon!

The barrel frame is unremarkable except that it is infused with teflon. The swirl [...] is common in injection moulded plastics (it is called Splay), but is perhaps more visible due to the teflon reflecting more light.

A bit of a necro but might as well share the info. Some IBM UK Ms I have actually have the exact plastic included in the mold lettering of the barrel plates. It's PPO SPN422L supplied by GE Plastics (before they were bought out by SABIC). It's a wear resistant fluorocarbon alloy so Unicomp's claim checks out if they're still using the same stuff.

Datasheet: http://www.e-polymer.com/pdfs/SPN422L.pdf

Plastic, foam and rubber disintegrates with time and it gives off a smell, so I would say it is time for changing it.