[Milsurplus] MFP Varnish Experiment

[Tom Dawson]

Back in mid September or so some of the chaps here were discussing MFP 
varnish, whether is was very toxic and what solvents wee appropriate for 
removing it.

This got me thinking as to how tough it would be to reproduce a suitable 
varnish from "purchasable" stuff.

The MIL Spec referred to, MIL-V-173, specifies a tung oil, phenolic varnish. 
This sort of  varnish is much less common today than urethane spar varnish, 
but I was able to find a product, "Waterlox Original" Marine Finish which is 
a available online for about 33 bucks per quart that seemed to fill the 
bill.  You can get it from Wood Carvers Supply Stores from 
www.woodworker.com .

By itself, the varnish looks OK although not quite yellow enough to pass for 
the real thing.  Still, better than nothing.

MIL-V-173 calls out oxine copper as the fungicide.  I don't know for certain 
that this was the fungicide in the 40's but it looks to have been used in 
the 60's.  I've seen copper sulphate solutions used for hoof-fungus (Thrush) 
in horses, so a copper based fungicide makes sense.

There are all kinds of different trade names for this substance but I found 
a source for 8-Hydroxyquinoline, copper (ii) salt at one chemical supplier 
(57 bucks for 5 grams) and bit the bullet to see how it would work.

Mixed up 1 gram of the copper salt with 100 grams of the vanish, by weight, 
because the spec called for 1% oxine copper.  100 grams of the varnish just 
about fills up a small baby-food jar.

Turns out to be pretty close to the color of the varnish on an old RA-20 
that's been around here for 10 years or so.

Given the prices of the varnish and the fungicide, this comes to about 18 
bucks for 100 grams of home-brew MFP.  If the oxine copper doesn't make you 
choke, the price just might.  The 80 bucks/quart does not sound so bad.

The fungicide is not a hazmat, but you need to keep it out of the surface 
and ground water as it is very toxic to fish.  Also, it is very irritating 
to your lungs so you want to be sure not to inhale any of it.  (This 
presumes that you're crazy enough to try this at home after hearing the 
prices).

The varnish is pretty thick, so if you want to spray it (use a mask) it 
looks like mineral spirits is the stuff, or maybe xylene.  Mineral spirits 
is first on the list of ingredients, and xylene is last.

At any rate, it was a diverting experiment and I now have a hundred grams of 
a fairly authentic MFP varnish that actually contains a fungicide, and is 
not overly dangerous to work with.  If you're not planning on demonstrating 
your Military Radios in the tropics, the Waterlox ought to be adequate by 
itself, even if it is a little paler than the mix with fungicide.


Happy Holidays.

Tom
WB3AKD