Dealing with a stain on an IBM Model M case?

lemur · 08 Oct 2016, 11:10

Greetings!

I've got an '89 Model M that I'm working on getting fresh and outside of an order for a new membrane from unicomp the only thing I'm not sure of how to fix is some staining on the case.

At some point in this boards distant past something appears to have splashed on it, causing it to stain the plastic.

When looking on the board on an angle in the light you can't see anything on top of the plastic, i.e. it's not paint.

I'm a bit colorblind, but it has a slightly purpleish color.

Anyone got an idea on what could be done about this?

There are some splash marks in a few places on the board, but in the image this is the largest mark.

: model m case stain; JWdR8ss.jpg (149.98 KiB) Viewed 2734 times

chzel · 08 Oct 2016, 11:36

Welcome!
Try some "magic eraser", they are melamine sponges that are slightly abrasive and will remove it from the surface without hurting the finish. If it's deeper I have no idea what you can do...

Alkhar · 08 Oct 2016, 12:37

You can buy them in bulk here : http://www.ebay.com/bhp/melamine-sponge

fohat · 08 Oct 2016, 14:57

chzel wrote: ↑
Try some "magic eraser", they are melamine sponges that are slightly abrasive and will remove it from the surface without hurting the finish. If it's deeper I have no idea what you can do...

I will disagree with this. They are indeed abrasive and can wear down the texture surprisingly quickly.

The problem is that the stain went into the "valleys" of the texture, too, and you may have to cut down the "mountains" to get to the valleys.

I would try a few solvents first, starting with soap and water. Take the case off and soak it for a while. If those stains are fruit juice, try bleach next. Then alcohol, which is good for many inks, citrus oil, work through a few different ones.

Almost all solvents are going to be bad for plastic, so work quickly and remove all residues as soon as possible at the end of each iteration.

XMIT · 08 Oct 2016, 15:18

So, the Model M shell is usually PVC plastic. It stands up to alcohol and acetone. MEK, I don't know, haven't tried it.

Melamine sponges are indeed abrasive. The key is that they are a light abrasive. The damage to the finish should be minimal if used lightly. Only use abrasives as a last resort when other solvents have failed.

I've definitely worn a couple of Model Ms shiny from using melamine pads or Scotch Brite pads too enthusiastically but these were boards that could not be cleaned any other way, including the back side of an SSK.

chzel · 08 Oct 2016, 18:20

I still have to seriously mark a case from melamine foam. I use it always wet and with very light pressure. And that is after I have tried a kitchen sponge with the usual solvents.

Elrick · 09 Oct 2016, 05:08

lemur wrote: ↑Greetings!
I'm a bit colorblind, but it has a slightly purpleish color.

Anyone got an idea on what could be done about this?

There are some splash marks in a few places on the board, but in the image this is the largest mark.

JWdR8ss.jpg

Suspect it looks like office pen ink or something from a bubble jet printer mixed with some sort of cleaning solution. In any office the clowns use just about anything that are entirely oil-based in nature. Hence the way it has already soaked through into the surface of that poor Model-M.

Only way to remove it is to use a powerful solvent to leach out the colour but be aware it might also attack the plastic casing as well.

Personally have always used "Eucalyptus Oil" to remove almost anything from certain plastics BUT you need to neutralize the Eucalyptus Oil (water and soap) before it goes too far and starts to deform your plastic housing.

lemur · 09 Oct 2016, 05:19

thanks everyone.. that should be plenty of info to start with

1391401 · 10 Oct 2016, 03:27

Try alcohol. I've removed all sorts of stains from my Model M's over the years, and it won't damage the case. If it's ink based, that'll remove it.

andrewjoy · 10 Oct 2016, 15:46

The magic erasers must be used with plenty of water ( or a solvent like rubbing alcohol), other wise they will wear it down very quickly. With liquid they are nowhere near as abrasive and can be used. I have used them even on a model F to remove stains and they are painted , just don't be heavy handed and you will be ok.