From: "Barry Ornitz" <ornitz@usa.net>
Newsgroups: rec.antiques.radio+phono
Subject: Re: voltage rating of enameled wire?
Date: Sat, 6 Jan 2001 20:29:53 -0500

"Gene Warner" <warn@ridgenet.net> wrote in message
news:938ea7$i2v$2@delphi.ridgenet.net...
> Wasn't the stuff applied to bare copper wires for motor and tranformer
> windings actually called Glyptal? At least most all Govt. Specs called
> for it. I recall ontime looking up the Glyptal Specification and I think
> the dialectric strength exceeded plain electrical varnish by quite a few
> hundreds of volts. The Glyptal I am familar with came out of the can red
> in color. It is also what gives gives the innards of well used govt.
> electronics that distinctive oder. They even sprayed the stuff on
> pre-insulated under chassis wiring primarily to tropicalize the
> equipment. Perhaps if Zenith and other mfgs. had put it on their rubber
> insulated wiring we restorers wouldn't be
> gnashing out teeth today over crumbling insulation.
> R\Gene

Glyptal is merely a trade name for an alkyd varnish.  The name comes from
GLYcerin and PhThALic acid which were combined in a condensation
polymerization to produce the raw resin.  Its voltage rating is no higher
than regular alkyd varnish.  The red color is often obtained by adding red
lead.

The tropical coating is known as MPF, moisture and fungus proofing.  It was
originally an alkyd varnish to which had been added copper naphthnate as an
anti-fungus agent.
Today if you want to recreate this look, especially with military
equipment, use urethane varnish to which has been added some yellow and
green dye.

Glyptal and MFP would not have prevented the crumbing insulation seen in
antiques.

        Dr. Barry L. Ornitz     WA4VZQ     ornitz@usa.net