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Old 25th Nov 2017, 5:13 am   #6
Argus25
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Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
Default Re: Varnish on top of oil, for high dialectric strength and looks

Quote:
Originally Posted by astral highway View Post
I'll immerse a pulse transformer in transformer oil (which is a very light grade), let the excess drip out for a few days and then attempt to overcoat with the same varnish.
One option is to test the oil you are using, linseed or low molecular weight transformer oil (which you can scavenge out of car ignition coils if you don't have any on hand) to see if it mixes with mineral turpentine (I think called white spirits in the UK) and I think both do.

I have diluted linseed oil with mineral turps to repair very dried out speaker cones to give the paper its original quality. Having a lower molecular weight, the turps dries off, leaving the small amount of evenly distributed linseed behind, it can't be too much linseed, just a little is required, probably about 1 part of linseed to 30 to 50 parts of turps.

In any case, for a high voltage transformer you could dilute the transformer oil with turps, this will help it impregnate the windings, with the turps carrying in the oil, then let the turps component evaporate off for a day or two, to leave the oil behind, before you use the marine varnish on it.

(have a look at the Bush TV22 lopty thread, turps is fine on a high voltage winding prior to varnishing it)

Contrary to popular belief, some oils will not stop paint sticking, if there is a thin residue of oil left, because its miscible with the varnish or paint and dissolves into it, that is if it is an oil based paint or varnish. It is just if there is too much oil there the paint will never set and remains tacky.

The main thing to remember is that "like mixes with like" so non polar hydrocarbon chemicals tend to mix with each other, and polar compounds, including water mix with polar compounds.

(One interesting thing, more substances dissolve in water than any other solvent, so never underestimate the cleaning power of a lightly damp cloth which also has a low risk of attacking plastics).
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