Tar for coil potting

[Jim11787]

I’ve read posts and can’t seem to find the tar local to me. I’m looking to buy enough to rebuild 8 or so coils. Anyone have a small piece they are willing to sell me?

[Charlie B in N.J.]

If you haven’t started yet and just need it for a capacitor replacement here’s what I’ve done about a dozen times: first carefully pry off the narrow side of the case opposite the brass buttons. A putty knife between the tar and the wood does wonders. Once off tar picking is easy. I leave the glass insulator in place as the caps I’ve used left enough room. Reclaim every piece of tar you chip out. Work on a large cardboard or plastic but save it all. Solder in the cap and use wood spacers to take up most of the open space. The collected tar goes into a small tin can with a spout bent into the top. A vice grip makes a good handle. OUTSIDE use a propane torch to melt the tar. It will go liquid quickly and smoke like hell. Of course the coils must be lined up and ready to receive the tar. I’ve never needed to buy any tar and don’t do enough coils to need a chunk of it hanging around.

[Jim11787]

If you haven’t started yet and just need it for a capacitor replacement here’s what I’ve done about a dozen times: first carefully pry off the narrow side of the case opposite the brass buttons. A putty knife between the tar and the wood does wonders. Once off tar picking is easy. I leave the glass insulator in place as the caps I’ve used left enough room. Reclaim every piece of tar you chip out. Work on a large cardboard or plastic but save it all. Solder in the cap and use wood spacers to take up most of the open space. The collected tar goes into a small tin can with a spout bent into the top. A vice grip makes a good handle. OUTSIDE use a propane torch to melt the tar. It will go liquid quickly and smoke like hell. Of course the coils must be lined up and ready to receive the tar. I’ve never needed to buy any tar and don’t do enough coils to need a chunk of it hanging around.

Thanks Charlie. I did save what I took out of one I took apart. The new cap is lather in diameter and I have to remove the glass plate. I considered using wood fill pieces of plexiglass and reuse what I can salvage. If someone is willing to part with a little chunk of tar it would make it easier. Thanks for taking the time to explain your process. The only reason I’m doing a few coils is to learn more. I only have the one car.

[Craig Leach]

Hi Jim,
I got carried away removing the tar from a Atwater-Kent coil and ruined the wood but I have the tar & some of the parts. there is
1# 11oz of tarThat I will be happy to part with. I have no idea what the going price of coil tar is?

Craig.

[Moxie26]

New capacitor , soldered leads , and re-potted with hot tar

[KWTownsend]

I add wood spacer blocks so less tar is needed.

[Moxie26]

Later made Plastic case coils... Capacitor, replacement and potting

[mtntee20]

Drive around Industrial parks, commercial buildings, and any large flat roof buildings until you find roofers working on the roof with a "Tar Pot" set up on the ground. Buy a box of donuts, talk to the guy on the ground working the tar pot, and TRADE him the donuts for some of the tar he is putting INTO the pot. They usually break up the tar cylinders with an axe and there are always small pieces on the ground. I'll bet a box of donuts will get you a lifetime supply.

Good Luck,

[Jim11787]

Drive around Industrial parks, commercial buildings, and any large flat roof buildings until you find roofers working on the roof with a "Tar Pot" set up on the ground. Buy a box of donuts, talk to the guy on the ground working the tar pot, and TRADE him the donuts for some of the tar he is putting INTO the pot. They usually break up the tar cylinders with an axe and there are always small pieces on the ground. I'll bet a box of donuts will get you a lifetime supply.

Good Luck,

Thanks

[J1MGOLDEN]

Tar does burn good when warmed up.

Tar can also explode when it is warmed too fast.

That kind of makes it not being able to be mailed in the U S Post Office.

[TRDxB2]

A solar flare hit me & was wondering if silicone casting material would be a good choice for filling a coil unit. Its non-conductive and would be easy to remove later if needed be. It could be applied in two sessions like making a mold, to make it even easier to remove. Tar was about the only solution back then as an insulator.

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Maybe ?
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[Moxie26]

I think the main question is how would the silicone or the aerosol filler adhere with the tar that's in the coil to make one solid unit.

[Jim11787]

Not sure how good foam filler would resist vibrations. It might turn to dust where it attaches to wires.

[TRDxB2]

I think the main question is how would the silicone or the aerosol filler adhere with the tar that's in the coil to make one solid unit.

Why do they, or other options, need to adhere to any residual tar that's in the unit? The purpose of the tar is just to prevent things from moving around. Its just a filler that is non conductive as the other options. I'm saying fill the box.
The foam expands and would prevent wires etc from moving

[Moxie26]

After replacing the condenser, soldering the connections, repotting with Hot tar will assure the adhesion to the tar in the rest of the coil unit and this way from Rocky road, vibrations and engine vibrations will eliminate wire breakage inside the coil

[Craig Leach]

Some time it's best to let sleeping dogs lie. James Goldens post about the mailability of potting tar is spot on. I asked USPS & UPS about
shipping it & the response is that by law it can only be shipped by ground, must be declared as HAZARDOUS & must be accompanied by the
manufactures MSDS sheets!
This means you can not ship coils legally without the declaration & MSDS sheets.
I know this sounds as stupid as you can get but this is what we get when we let environmentalists & politicians control the EPA, NTSB & DOT.
Hopefully Ron Patterson & Brent Mize can shed some light on this issue.
Please don't shoot the messenger. & I hope the USPS & UPS employees don't know what they are talking about but the USPS employee was on
the phone for almost 1/2 an hour.
Craig.

[Bob McDaniel]

I wouldn't use the expanding foam because it will be a b×#@&* to remove later if you or the next guy need to ever work on that coil again.