"Dave Platt" wrote in message
...
I read that old 78 LP's broken into pieces & mixed with a particular
solvent
was used as coil dope. Does anybody remember which solvent was used & how
affective it was?

78s were often made of shellac, and the usual solvent for shellac is
denatured alcohol. I believe that some other 78s were made from
cellulose acetate... for this material I believe that acetone would be
a usable solvent.

My understanding is that commercial Q-dope uses polystyrene, dissolved
in a suitable solvent.

Toluene.

According to an article by Barry Ornitz WA4VQZ (the text is at
http://yarchive.net/electr/coil_dope.html), a very acceptable coil
dope can be home-brewed by dissolving ordinary polystyrene "packing
peanuts" in either toluene or acetone (the latter is less toxic).

Thanks for mentioning this archive Dave. I strongly suggest that before
anyone tries making their own Q-dope, they read ALL the safety information
given there. And yes it really does take several weeks for the "cotton
balls" to fully dissolve.

What I think that "Spin" was referring to was that early pressings were
made from cellulose acetate. Acetone would be the solvent of choice here.
I was not aware that phenol formaldehyde thermoset resins were ever used
for records, but if you find any, they won't dissolve in anything!

As for the worry that when Styrofoam is dissolved in a solvent, styrene is
released - forget about it. Styrene is rather volatile and has a VERY
distinctive odor. You would smell it if more than a trace amount were left
in the peanuts. Polystyrene does not depolymerize by dissolving it in a
solvent.

Devcon's Duco Cement is nitrocellulose dissolved in acetone with a little
camphor as a plasticizer and with small amounts of isopropanol and
1-methoxy-2-propanol acetate thrown in for good measure. If you only need
a few ounces of Q-dope, Duco Cement is a suitable substitute.

Roy Lewallen, W7EL, dipped a number of coils in various materials (RTV
silicone, epoxy cement, Q-dope, hot melt adhesive, etc.) a while back and
then measured their losses with a Q-meter. If Roy can find his old
article, perhaps he can post it again.

--
73, Dr. Barry L. Ornitz WA4VZQ

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