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Old 17th Feb 2024, 2:53 pm   #1
antiqueOM
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Default Tar removal from Mica Trim Capacitor

Need to clean a MICA trim capacitor which is caked in TAR from a leaky
capacitor bank in a RCA receiver. One suggestion is to use odorless mineral spirits. Comments?

Thanks,
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Old 17th Feb 2024, 5:05 pm   #2
Bazz4CQJ
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Default Re: Tar removal from Mica Trim Capacitor

My preferred approach here in the UK would be to use what we call "White Spirit" (WS) to remove tar (check Wiki to see what the translation is to US terminology). White spirt is commonly used in the UK (domestically) to thin many kinds of household paints, but it is a relatively kind solvent. I use it on my car to remove tar and it never affects the paint work.

Perhaps it might be kind to the component to dilute the WS with maybe 50:50 with isopropyl alcohol - hard to say.

I'm not sure what odourless mineral spirits is; don't think we use that term. WS is slightly stinky, but is good with tar. This advice offered is in good faith, and I am a chemist, but with the component being caked in tar, there could be some risks with any solvent.

Good luck,

B
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Old 17th Feb 2024, 5:23 pm   #3
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Default Re: Tar removal from Mica Trim Capacitor

White spirit (UK) = Stoddard solvent (US) = mineral spirit (US).

Cigarette lighter fluid (naphtha) may also be worth trying. Coleman Camp Fuel ('white gas') is very similar stuff.
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Old 17th Feb 2024, 6:34 pm   #4
antiqueOM
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Default Re: Tar removal from Mica Trim Capacitor

Excellent and many thanks for the replies. The Mineral Spirits with no odor, since there are no additional additives, is worthy of a try. If I am careful not to harm the mica sheets in this compression trimmer, I should be able to measure and verify success. A dilution with alcohol is worth a try. Will post results upon completion.
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Old 17th Feb 2024, 7:40 pm   #5
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Default Re: Tar removal from Mica Trim Capacitor

White spirit came in the traditional version, a low odour version and possibly a water based equivalent.

I would also like to know more about these alternative versions and the effect they would have on plastics, paint, markings, etc.
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Old 17th Feb 2024, 8:23 pm   #6
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Default Re: Tar removal from Mica Trim Capacitor

White spirit is my go to solvent for cleaning purposes and I've never had any problems with it dissolving anything.

Most dirt on vintage radios chassis etc, can be removed with just water though.
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Old 17th Feb 2024, 9:52 pm   #7
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Default Re: Tar removal from Mica Trim Capacitor

White spirit is just one of a huge number of petroleum distillates, so it's not that far removed from petrol/gasoline or paraffin/kerosene. It's volatile so it evaporates leaving little residue. 'Turpentine substitute' is basically the same stuff, and old school WD40 is mostly white spirit.
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Old 17th Feb 2024, 10:04 pm   #8
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Default Re: Tar removal from Mica Trim Capacitor

Quote:
Originally Posted by paulsherwin View Post
White spirit is just one of a huge number of petroleum distillates, so it's not that far removed from petrol/gasoline or paraffin/kerosene. It's volatile so it evaporates leaving little residue. 'Turpentine substitute' is basically the same stuff, and old school WD40 is mostly white spirit.
I'm not sure that turpentine should be regarded as the same stuff as White Spirt. It contains (some) terpenes, quite strong and stinky solvents. Just looking on Google, none of the Sheds seem to sell a product they call turpentine, but they can still be found (trades use? I suspect it was more common when we were kids!).

Odour-free mineral spirits seems to imply that some low levels of aromatic compounds have been removed, but I suspect the mixture will still handle tar. I always have some WS at hand.

B
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Old 17th Feb 2024, 10:09 pm   #9
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Default Re: Tar removal from Mica Trim Capacitor

Turpentine substitute. I haven't seen actual turpentine for a very long time.
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Old 17th Feb 2024, 10:25 pm   #10
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Default Re: Tar removal from Mica Trim Capacitor

I would be cautious about regarding the substitue as WS. This is a comment I found a website in just seconds;

They will have the same ingredients both are distillates of crude oil at the bottom line, if you really want to see the difference wash 2 brushes one in turps subs and one in white spirits, the turps brush will feel oily and require a lot of soap to bring it really clean, where as the white spirit will come out with just a tiny drop of soap".

The underlying issue here is that they are all complex mixtures with no specific chemical compositions, probably coming out of China at rock bottom prices; who knows what's really in them? With turpentine not being commonly sold, why still sell "Turps Subs" if it's not different in some way?

For cleaning the front panel of your favourite Vintage Radio, or other valued asset, I'd stick firmly with WS.

B
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Old 17th Feb 2024, 10:45 pm   #11
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Default Re: Tar removal from Mica Trim Capacitor

People are just lazy, and it's easier to sell them 'turps subs' for paint related usage than 'white spirit', which sounds like something expensive and exotic bought in a pharmacy. I suspect they're exactly the same stuff nowadays. Of course, these names are non specific generic terms and the specific chemistry involved is unknown.

Obviously all solvents need to be used carefully.
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Old 18th Feb 2024, 1:23 am   #12
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Default Re: Tar removal from Mica Trim Capacitor

Perhaps I've been scarred by one bad experience. Some years ago, I bought an aerosol can of "label remover" from Maplin. I'm pretty sure that was based on terpenes (citrus smell). At first, I used it cautiously and it was good and caused no problem. Moving on a bit too fast, I sprayed it on the small polystyrene drawers that are typical of component drawers.

Bad outcome; all the surfaces went badly opaque. Not a total disaster, as I was taking labels off to put new ones on, and transparency didn't matter, but I was not pleased with myself.

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Old 18th Feb 2024, 8:57 am   #13
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Default Re: Tar removal from Mica Trim Capacitor

I have some purple coloured turps that I use for making the flame under the boiler of a model steam engine. The smell takes me back to my early childhood and visits to the clinic for injections

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Old 18th Feb 2024, 9:36 am   #14
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Default Re: Tar removal from Mica Trim Capacitor

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I have some purple coloured turps that I use for making the flame under the boiler of a model steam engine. The smell takes me back to my early childhood and visits to the clinic for injections

Aub
That sounds more like Methylated Spirit, known outside the UK as ‘Denatured Alcohol’.

It burns with a clean, almost invisible, flame.

It’s used to dissolve shellac flakes to make French Polish.

Back when petrol and paraffin blow-lamps and Primus stoves were commonplace, it was used to prime ‘them’.

Handy for removing spirit-marker stains. (‘Sharpies’).
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Old 18th Feb 2024, 10:40 am   #15
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Default Re: Tar removal from Mica Trim Capacitor

Sorry, brain fade David . Yes, I meant meths

Aub
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Old 18th Feb 2024, 12:32 pm   #16
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Default Re: Tar removal from Mica Trim Capacitor

When IPA, Methylated Spirit, White Spirit, Lighter fuel etc struggle to do a particular cleaning job I then use Cellulose Thinners (CT) which does a good job generally.

CT is normally used to thin down cellulose based paints and varnishes. It is a mixture of various solvents and I guess the actual mixture and % strengths of each chemical will vary depending upon who manufactures the CT.

It has a very strong odour and is quite volatile I believe so when used should be in an open area or well aired room.

CT may damage certain plastics so should be used with care.

In one tape recorder large potted CR snubbers had badly leaked a horrible tar like substance, I had a difficult job cleaning it all up but CT certainly helped.

David
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Old 18th Feb 2024, 2:46 pm   #17
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Default Re: Tar removal from Mica Trim Capacitor

I've also used the wife's acetone - the stronger stuff.

Aub
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Old 18th Feb 2024, 2:55 pm   #18
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Default Re: Tar removal from Mica Trim Capacitor

Car brake cleaner - I think that it is Xylene - is also useful, that's what I used recently to remove the red gunge that had oozed out of the nasty bathtub capacitors in an AR88.
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Old 18th Feb 2024, 6:13 pm   #19
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Default Re: Tar removal from Mica Trim Capacitor

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I've also used the wife's acetone - the stronger stuff.

Aub
Is that nail varnish remover ?

David
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Old 18th Feb 2024, 6:29 pm   #20
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Default Re: Tar removal from Mica Trim Capacitor

Nail varnish remover is mostly acetone, but can have other ingredients.

It can attack some plastics.
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