[R-390] [GreenKeys] Removing MFP (fwd)

[Nick England]

You just need a bottle of "suitable solvent" -

SIMCO http://www.simcocoatings.com/t-838.html says:
Solvent Type: Xylene/Aromatic/Aliphatic Hydrocarbon

Army Technical Manuals usually say remove MFP varnish by scraping with
a knife blade (for a small area) or using trichloroethylene as a
solvent for larger areas.

A study of MFP removal for circuit board repair tried 28 solvents as
chemical strippers, of which about 50% worked.
www.dtic.mil/dtic/tr/fulltext/u2/283476.pdf
It also says a "cool" soldering iron 35-400 deg worked better than a
"hot" 600 deg one at softening the varnish.

Finally, any number of military manuals (including for the SP-600)
talk about touching up the MFP afterwards, but never mention anything
special for unsoldering.

======================
The applicable document on MFP treatment seems to be:
MIL-T-152B 31 March 1961
SUPERSEDING MIL-T-152A 14 December 1955
MILITARY SPECIFICATION - TREATMENT, MOISTURE- AND FUNGUS-RESISTANT. OF
COMMUNICATIONS, ELECTRONIC, AND ASSOCIATED ELECTRICAL EQUIPMENT

Which unhelpfully just says:
"Resoldering of wire connections shall be made only after cleaning the ends of
wires and terminals with a suitable solvent to remove old varnish."

MIL-T-152B says to use:
MIL-V-173 - Varnish. Moisture-and-Fungus-Resistant (for the Treatment of
Communications, Electronic, and Associated Electrical Equipment).

MIL-V-173C (1969) says:
This specification covers one type of moisture-and-fungus-resistant
varnish consisting of a para-phenyl phenol-formaldehyde resin in
combination with tung oil and suitable solvents which has been made
fungi static by the addition of 7.0 +/- 1 .0 percent salicylanilide or
one percent copper 8-quinolinolate, for the treatment of assembled
communications, electronic, and associated electrical equipment.

3.1.1 Volatile content. The volatile portion of the varnish shall be any
suitable solvent or solvents: however, methanol (wood alcohol), benzene
(benzol), chlorinated hydrocarbons, or other highly toxic solvents shall not
be used.

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

FWIW, A 2008 discussion on antique radio forum turned up the following comments:
1) "In WWII a mixture of Tung oil and copper Napthalate was used"
2) "In 1950's-60's aircraft -  a two part resin compound, and not easy
to get off en mass. you can soak it in MEK or Acetone but probably not
a good idea since that stuff will attack just about anything that
isn't metal."
3) "Use a xacto knife or similar tool to get enough off to put a
soldering iron on the bare solder joint. The MFP will then become very
plyable and it can be easily cleaned off after removing the component
or wire".
4) "I've always used Acetone to remove MFP before soldering."