[TowerTalk] Scotchkote and Liquid Tape

Kurt Andress ni6w@yagistress.minden.nv.us
Wed, 04 Nov 1998 00:19:14 -0800

To all connection Goopers,

My apologies for sending off my last post without finishing it. Got distracted by
the XYL, and clicked on the wrong button. Awh shucks!

John (KF4MZD)  offered some good comments about the 3M Cold-Shrink Wrap material.
I have not used it and, therefore, cannot comment.

I'm sure there is certainly more to consider on this subject, than has been
recently presented.

Back to finishing my comments about Scotchkote, and my experience with it.

What makes the method I've been taught and suggested so effective is the seal
that is obtained between the substrate (coax jacket and connector metal parts)
and the tape overwrap. The Scotchkote has been designed to tenaciously bond to
clean metal parts, coax jackets and the adhesive on the vinyl 3M tapes. Good or
cheap PVC tapes don't work so well with Scotchkote. Yet, it seems to work fine
for sealing non-contaminating jacketed PVC coax cables.

The way water gets into the connection is along the primary interface (first
layer of tape against the cable jacket, connectors, and tape). We can put
hundreds of layers of tape and some kind of GOO on a connection, but the only one
that really counts is the first layer!
After that, the second most available path for moisture into the connection is
between the wraps of the tape. But if all of them are wrinkle free and bonded to
the connection substrates, there still is no path for the moisture migration.

The UV deterioration problem with the Scotchkote goes away if we put it
underneath the tape, where the UV can't get to it! The stuff brushed over the
outside is just for giggles.

Every time I have taken apart a connection that had the Scotchkote applied first,
before the tape wrap, I have seen the tape adhesive & parts of the tape separate
and remain bonded to the connection. This tells me that the Scothkote provides a
better bond to the cable and connectors than the tape adhesive bonds to the tape!

Sure, one has to slice the taped connection to get it apart, like a banana peel.
That's because the tape is so strongly bonded to the connection that simple
peeling of the wrapped tape is impossible. This strongly suggests that the
primary seal against water migration on the first layer is pretty good!

For those that really hate having some black stuff stuck to the outside of their
connections, after 10 years, by all means use something else.
What puzzles me the most about this is that 3M doesn't suggest this method of use
on the can of Scotchkote.

It took an old Motorola field service technician to show me how this stuff really
works best.
A 10 year old connection that has some black stuff on the outside and is shiny on
the inside is pretty FB at my QTH!

For connections that can't be suitably tape wrapped, the Liquid Tape is probably
better because of its UV resistance, if it actually can bond to the metals of the
This usually requres complete removal of the joint compound, from all exposed

73, Kurt

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