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#1
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![]() "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 |
#2
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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 |
#3
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![]() "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 |
#4
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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 |
#5
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![]() "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 |
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