[ARC5] Tropical Coating -MFP

[J. Forster]

Certainly the stuff would increase the stray capacitance of wires, because
you are replacing the air between the copper conductor and ground with a
material with a material of higher dielectric constant. The effect would
be most noticable with heavy coats on wires close to grounded objects.

I wonder if the stuff might contain a Mercury compound as a fngicide? Some
paints do/did.

-John

=============


> 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
>>
>
> Robert & Susan Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
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