[volt-nuts] Oil and molded components

WB6BNQ wb6bnq at cox.net
Wed Dec 16 21:52:23 UTC 2009

Ed Palmer wrote:

> snip
> >
> Earlier in this thread there was mention of resistors that were coated
> with shellac or lacquer.  Would it be possible to coat a molded resistor
> to seal it from air, moisture, or oil?  Perhaps one of the high-voltage
> varnishes like this:
> http://www.action-electronics.com/msds/GC10-9002%20Spec%20Sheet.pdf
> Ed

Hi Ed,

Let me forewarn everyone that starting research in WIKI over such subjects will
get you buried into hours and hours of torture from which your brain will
eventually emerged with a headache.  While WIKI is quite good for a general brush
of knowledge, it is by no means a complete treatise of any subject.

Interestingly WIKI (information) groups shellac and varnish as kissing cousins.
What surprised me is shellac, made from an insect {uck} is used to coat candy.
So watch out for those M&M’s !

The varnish page was less disturbing.  However, both do not really answer the
questions we have for our applications.  So what is needed is to approach or
search companies that provide shellac/varnish materials for the electrical
industries and see if there are any “WHITE” papers describing the details of such

It seems that there are many variations of shellac/varnish {all considered
resins} with varying properties and clearly shows the need for a chemist.  I know
one real chemist.  I met him at a favorite little local restaurant dive where he
hangs out.  However, when you ask him questions you mainly get incomplete phrases
{forget sentences}, so I think he has sniffed a few to many formulas.  In all
fairness, he really is a nice person.

So the upshot is some research is needed to get a better grip on the subject.  I
think not one formula fits all.  GC electronics has a number of “coatings” for
different purposes but seemingly all similar, at least their writeups look that

That is why I hate painting.  Just too many choices !  AND never, ever take a
female with you to a paint store.  Unless Fluke, Genrad and others would talked
about why they use such-and-such for their products, we are left up to our own

Well worth the read is the WIKI for shellac:


And for varnish:


For mineral oil:



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