[ARC5] Tropical Coating -MFP

[WA5CAB at cs.com]

Ken,

I think that the thread ran on the MILSURPLUS list.  But in any case, I 
don't recall it being mentioned that in certain sets 60-70 years on, it can 
cause problems due to acting as capacitors to ground.  I just (almost) finished 
repairing a BC-611-F.  In general, any point in the circuit of that thing 
that should show open or at least greater than 5.7 megohms to ground reads 
about 5 megohms on a Simpson 260.  Several other heavily MFP coated units 
(model letter unimportant) have had to have the next higher frequency antenna 
coil installed before the antenna tuning would peak properly.

In a message dated 2/21/2010 11:51:50 AM Central Standard Time, 
kgordon2006 at verizon.net writes: 
> On 21 Feb 2010 at 11:19, Gene Smar wrote:
> 
> >      What your are probably seeing is what is known as MFP - Moisture 
> and 
> >Fungus Proof - coating.
> 
> MoistureFungusProofing - MFP
> 
> Yes. I love the smell of that stuff.
> 
> >  It was applied after assembly to all WWII and 
> >Korean War vintage milrads.
> 
> Not necessarily all. It depends on when it was applied. Early in the war, 
> it 
> went on gear going to the Pacific and other high-humidity areas. Later, as 
> 
> more became available, it was applied to all gear.
> 
> >      Some time back there was a thread hereabouts that described the 
> exact 
> >components that went into the coating.  IIRC, it was bees wax and 
> varnish. 
> 
> It also contains formaldehyde. 
> 
> As I remember it, our previous discussion on the subject was also attended 
> 
> by an industrial chemist who advised against our attempting to recreate 
> the 
> goop as the process was somewhat dangerous. 
> 
> Either when being made, or when liquid, MFP is poisonous. It isn't when 
> dry, 
> and any fumes from removing it with heat to solder are not dangerous 
> either.
> 
> I may have those discussions (and I am not ever sure they were from THIS 
> list) saved in my voluminous files. (I am in information junkie).
> 
> If we are interested enough I will dig out the formula for you.
> 
> In any case, the stuff was almost completely effective for its purpose, 
> which 
> was to prevent moisture damage to electronic gear and the subsequent 
> appearance of copious quantities of fungus which made the gear inoperable.
> 
> In any case, I love the smell of the stuff.
> 
> Ken Gordon W7EKB
> 

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