Cleaners for plastic?

[MikeK]

Before my part arrives for fixing my Keithley 175A (https://www.eevblog.com/forum/repair/keithley-175a-not-working/) I might as well clean up the case and display.  I have these cleaners in my house:

1. Simple Green
2. Isopropyl alcohol
3. Windex (with Ammonia-D)
4. Formula 409
5. Sprayway Glass Cleaner (Ammonia Free)

Will any of these definitely ruin the plastic?  I'm especially worried about the LCD.

[David Hess]

Alcohol will fog some plastics.  I like to use naphtha, which is plastic safe, and then water with a little bit of dish soap, but often I use Windex because it is more easily available.

[MikeK]

Thanks.  I thought there was something about ammonia being bad?  The glass cleaner (Sprayway) that I use for my car brags about being ammonia-free, which I thought was to prevent damaging rubber and plastic.  I had no idea naphtha was plastic safe.  Good to know.

[jpanhalt]

All of the solvents the TStarter name are OK on most plastics.  The polystyrene is quite sensitive.  Jewel cases used for CD's are an example.  I have never tried isopropyl alcohol, but even light naphtha (e.g., VM&P Naphtha) will cause slight fogging.

If you are just removing accumulated dust, finger prints, etc. I would recommend any of the water-based cleansers.  If you need to remove goo, I typically use naphtha but be careful on any clear plastic.  It can cause crazing, which doesn't necessarily appear immediately.  Butter is another very mild solvent for goo.  The mildest "solvent," of course is not to use any solvent at all.  Use a piece of tape (e.g., masking tape) sticky side out.  Press and quickly pull off.  You might need to repeat.

[David Hess]

Thanks.  I thought there was something about ammonia being bad?  The glass cleaner (Sprayway) that I use for my car brags about being ammonia-free, which I thought was to prevent damaging rubber and plastic.  I had no idea naphtha was plastic safe.  Good to know.

I have never had a problem with ammonia cleaners like Windex that I remember.

I have never tried isopropyl alcohol, but even light naphtha (e.g., VM&P Naphtha) will cause slight fogging.

I have had problems with VM&P naphtha being contaminated with other things, while purer naphtha was not a problem.

Use a piece of tape (e.g., masking tape) sticky side out.  Press and quickly pull off.  You might need to repeat.

Heating with a heat gun helps soften any adhesive.

I have read that glacial acetic acid is good for removing labels, but it never worked well enough to justify dealing with it.

[jpanhalt]

Re: naphtha
Of course there are various purities.  I tend to use the KleanStrip version and avoid Sunnyside solvents whenever possible.  Similar cleaners are sold in automotive finish stores under various names.  Some contain a small amount of toluene or xylenes.  Those might be a problem on polystyrene.

[MikeK]

Windex and Simple Green worked just fine.  Tried everything on my other meter, but can't get this fossilized label off.

[jpanhalt]

Gentle heat can help.  After that, you run the risk to damaging the plastic with stronger cleaners.  Just leave the label.

[MarkF]

I use WD40 to remove store pricing labels.
You might need to let it soak for a while.
Then clean with one of the cleaners discussed here.

[DaJMasta]

For label adhesive residue, something with lemonene is usually my preference - something like Goo Gone.  You just wipe it on (it takes a couple passes to clean, so I usually apply to a paper towel and then use that), let it soak, and the label gunk should be softer and less sticky, and usually comes off with a little manual scrubbing or peeling.

[Wallace Gasiewicz]

Oily cleaners like Googone can help a lot. Some folks use Mineral oil, Vegetable oil, peanut butter, butter. The idea is to let it soak in the oily solvent, Put a small piece of paper towel on the spot and saturate it with the oily solvent.

[HighVoltage]

I have several of the old brown Keithley instruments.
They clean up very nicely with some alcohol.

And when I am done cleaning, I wipe the plastic with some very thin oil (Liquid Paraffin or White Oil), let it sit for a few hours and then wipe it off with a clean cotton cloth.

After this procedure, the housing will look like new and will stay like this for years to come. Somehow this brown plastic material absorbs the thin oil well.