"Avery Comarow" wrote in message
...
On Feb 13, 10:41 pm, "Richard Knoppow"
wrote:
At some time in the recent past there was a discussion
in this or the antique radio group about coil dope. As a
result I tried making some. ...What I did was to dissolve
polyfoam shipping material
in a mixture of MEK and xylol. I chose these two solvents
because both were listed on the lable of some old
commercial
coil dope.

Richard Knoppow

Proportions, please?

Mostly MEK. I added a little Xylol (AKA Xylene) because
I thought I saw it listed in an MSDS for coil dope. However,
the MSDS for the General Cement product lists only MEK
although the thinner is Toluene. If I do it again I will use
straight MEK. I added the styrofoam until the stuff got to
what seems to be the right consistency, about like honey.
Mine came out a sort of gray color rather than clear but the
pictures of the General Cement Q-Dope also look gray. My
styrofoam was scraps of shipping material from something I
mail ordered. It is amazing how quickly it dissolves, at
least at first. I used a small, wide-mouth, bottle I got
years ago. I would test the cap of any container you plan to
use with a little MEK to make sure it will not be attacked.
MEK is a rather wide spectrum solvent which will dissolve
latex and a number of other substances.
I will make some measurements when I have a little time
to see if my dope affects coil Q. Commercial dope has very
little effect.
MEK is available at any paint or hardware store and
styrofoam abounds. One can use styrofoam cups but I think a
sufficient supply can be found free.
I tried making my own after working on an old
Hewlett-Packard signal generator (606-A) where the high band
coils must be fastened down with it after adjustment. I
found none of my usual local suppliers had the stuff. I have
since found that Action Electronics, in Anaheim CA carries
it but that is a 30 mile drive from here. So, I decided to
make my own.



--
Richard Knoppow
Los Angeles
WB6KBL

Richard Knoppow wrote:

Richard Knoppow

Proportions, please?

Mostly MEK. I added a little Xylol (AKA Xylene) because
I thought I saw it listed in an MSDS for coil dope. However,
the MSDS for the General Cement product lists only MEK
although the thinner is Toluene. If I do it again I will use
straight MEK. I added the styrofoam until the stuff got to
what seems to be the right consistency, about like honey.

A word of caution to anyone considering this: when starting this
procedure, fill the container only a third of the way with MEK. All
that polystyrene needed to thicken it up to honey-like consistency will
increase the volume a lot.

I have a half-pint mason jar that started with a third of MEK. I fed it
one and a half letter-sized inch-thick slabs of foam and it's still not
done.

--
David Griffith
--- Put my last name where it belongs

"David Griffith" wrote in message
...
Richard Knoppow wrote:

Richard Knoppow

Proportions, please?

Mostly MEK. I added a little Xylol (AKA Xylene)
because
I thought I saw it listed in an MSDS for coil dope.
However,
the MSDS for the General Cement product lists only MEK
although the thinner is Toluene. If I do it again I will
use
straight MEK. I added the styrofoam until the stuff got
to
what seems to be the right consistency, about like honey.

A word of caution to anyone considering this: when
starting this
procedure, fill the container only a third of the way with
MEK. All
that polystyrene needed to thicken it up to honey-like
consistency will
increase the volume a lot.

I have a half-pint mason jar that started with a third of
MEK. I fed it
one and a half letter-sized inch-thick slabs of foam and
it's still not
done.

--
David Griffith
--- Put my last name where it
belongs

I started with about half the jar filled with MEK.
Since I used styrofoam the displacement of the material
before it dissolves is much greater than after because so
much of it is air. The first pieces dissolved very quickly,
in fact it looked like Alka-Seltzer dissolving. Toward the
end it took a few minutes for each additional piece to
dissolve. The total amount is amazing until you remember
that its mostly air. After the first flurry of very quick
solution I added pieces about twice a day and just let it
alone between times. Of course with the cap on, MEK will
evaporate very quickly.


--
Richard Knoppow
Los Angeles
WB6KBL

Richard Knoppow wrote:

I have a half-pint mason jar that started with a third of MEK. I fed
it one and a half letter-sized inch-thick slabs of foam and it's
still not done.

I started with about half the jar filled with MEK. Since I used
styrofoam the displacement of the material before it dissolves is much
greater than after because so much of it is air. The first pieces
dissolved very quickly, in fact it looked like Alka-Seltzer
dissolving. Toward the end it took a few minutes for each additional
piece to dissolve. The total amount is amazing until you remember that
its mostly air. After the first flurry of very quick solution I added
pieces about twice a day and just let it alone between times. Of
course with the cap on, MEK will evaporate very quickly.

I stirred mine with a screwdriver and finished it in a couple nights.
Watching the first few chunks dissolve was rather amusing.

I don't know what sort of lid you used on the jar, but MEK softened up
the sealing compound. Based on what I found on a website on what sort
of gloves to use with MEK, I think butyl rubber caulk would be good to
keep the solvent from seeping out. Dissolve off the rest of the sealing
compound, then apply the caulk in its place. While you're waiting for
the caulk to cure, some foil on the jar should keep the MEK in place.
Or, even better, prepare the lid before mixing up the dope.


--
David Griffith
--- Put my last name where it belongs

"David Griffith" wrote in message
...
Richard Knoppow wrote:

I have a half-pint mason jar that started with a third
of MEK. I fed
it one and a half letter-sized inch-thick slabs of foam
and it's
still not done.

I started with about half the jar filled with MEK. Since
I used
styrofoam the displacement of the material before it
dissolves is much
greater than after because so much of it is air. The
first pieces
dissolved very quickly, in fact it looked like
Alka-Seltzer
dissolving. Toward the end it took a few minutes for each
additional
piece to dissolve. The total amount is amazing until you
remember that
its mostly air. After the first flurry of very quick
solution I added
pieces about twice a day and just let it alone between
times. Of
course with the cap on, MEK will evaporate very quickly.

I stirred mine with a screwdriver and finished it in a
couple nights.
Watching the first few chunks dissolve was rather amusing.

I don't know what sort of lid you used on the jar, but MEK
softened up
the sealing compound. Based on what I found on a website
on what sort
of gloves to use with MEK, I think butyl rubber caulk
would be good to
keep the solvent from seeping out. Dissolve off the rest
of the sealing
compound, then apply the caulk in its place. While you're
waiting for
the caulk to cure, some foil on the jar should keep the
MEK in place.
Or, even better, prepare the lid before mixing up the
dope.


--
David Griffith
--- Put my last name where it
belongs

Actually, I am not sure what the lid and gasket are
made of. This was a jar I bought at a local chemical supply
house that is now out of business (and sorely missed). I
tested both the cap and gasket with MEK before using the
jar, they seemed to be immune to it. Your suggestion about
using aluminum foil as a cap liner is a good one.
I just did a Google search for gloves suitable for use
with MEK and found a chart showing a variety of chemicals
and recommended gloves for use with them at:

http://msds.chem.ox.ac.uk/glovesbychemical.html

This lists teflon and butyl rubber as suitable for MEK.


--

--
Richard Knoppow
Los Angeles
WB6KBL