Solvent for dissolving asphalt tar?

Howdy,
I need to dissolve some asphalt potting tar off of a transformer (metal content). In the past when I have done this, I have used gasoline, which
does work. The usual technique is to put the unit in a bucket of the solvent and let it sit for a few days, brush off whatever is soft enough, and repeat until a sufficient amount of tar is removed to allow access to the innards.
Now, however, being somewhat more cautious, I am entertaining thoughts of using a less volatile solvent, in the interest of safety. Ideally, I won't be giving up too much solubility in the process
I have narrowed it down to a few choices, diesel, kerosene, naptha (Coleman fuel), or paint thinner (mineral spirits). Diesel would be about as cheap as gas, which is a plus, but I am unsure as to it's ability to dissolve tar.
Any thoughts on which would be the best solvent for dissolving asphalt tar?
Thanks,
Jon
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In order of decreasing speed (i.e., fastest first): naptha paint thinner kerosene, diesel
Not all that much difference, though. Go with the cheapest.
Bob
PS acetone would be faster than any of these, but way more expensive. And just as volatile/dangerous as gas.
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Umm - Spell Checker told me it was "naphtha", but I didn't believe it. Well, it's right & pronounced naf-tha or nap-tha. Learn & learn.
Bob
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wrote:

Hi, Jon. Are you sure it is asphalt tar? Older transformers I have worked on were potted in coal tar. Asphalt tar will cold flow and will really warm flow and make a mess when your transformer gets warm. Coal tar will not flow until it gets to a rather high temperature. It also doesn't dissolve in anything very easily. I am not sure if this makes any difference to you, but you may be able to Goggle a better solvent for coal tar.
Old radio batteries as well as older auto storage batteries used coal tar for sealing. It is also now considered a carcinogen and you can't get it anymore.
Good question, though.
Paul, KD7HB
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Well, I'm not entirely too sure, but it melts at about 250F-300F, and smells like the stuff the roofers use to seal cracks with. .
Jon
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wrote:

So, you could empty the goo with a drip pan lined with aluminum foil and an oven that will hold 300F for twenty minutes. I have at least one tar brick in the adhesives drawer that I got that way...
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whit3rd wrote:

I guess you are not married.
John
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Gotta quite drinking beer when I read these! I had to clean up the keyboard.
John wrote:

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Outside interests are a wonderful thing. Bridge Monday night, concert band Tuesday... I just have to make sure the smell is gone before she makes it home.
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wrote:

Some of us have a stove/oven in our shops for this very reason... to stay married <g>. I've even got m' own washer/dryer in here too.
Snarl
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Use the oven and he might not be....
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Use diesel and prepare to be amazed.

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On Tue, 4 Sep 2007 16:24:09 -0700, "Jon Danniken"

Coleman fuel is more volatile than gasoline.
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Stoddard solvent.
Note the word *solvent*.
That's its intended purpose.
Harold
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you are doing this backwards - (are you unpotting an NST? if yes, check the tesla list archives) - put transformer in freezer (or better yet liquid N2) and get it really cold, then take it out and tap the tar with a hammer - it will just shatter like glass - get most of it off that way, then use solvent - others have suggested proper solvents

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On Tue, 4 Sep 2007 21:19:46 -0700, "William Noble"

That works? Damn...fascinating! Thanks!
Gunner, who learns something cool everyday.

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After a Computer crash and the demise of civilization, it was learned
-0700 in rec.crafts.metalworking :

    Umm, have you priced N2 in liquid form? I've heard "it is cheap as beer" but they never say what kind of beer: Sludgwillers or a microbrew. But it was real neat when I poured the excess into my travel mug - sent a plume of fog out the opening. Cool enough I'm almost willing to go back over to assembly. Almost.
    But the freezer trick is a cool alternative.
pyotr
-- pyotr filipivich "Quemadmoeum gladuis neminem occidit, occidentis telum est. " Lucius Annaeus Seneca, circa 45 AD (A sword is never a killer, it is a tool in the killer's hands.)
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Sure no science, just age and experience. It seems that things closer together on the cracking tower dissolve or combine easier than things far apart on the tower. Diesel would be my first choice - closer to the tars and asphalts on the tower.
--
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Keep the whole world singing . . . .
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On Tue, 4 Sep 2007 16:24:09 -0700, "Jon Danniken"
<snip>

<snip> It is well to remember that there is no single compound that is "gasoline." Over the years it has changed from a totally petrolium distilate with possibly a littleTEL to a witches brew.
I also used to use gasoline to clean parts, but had some a few months ago that took skin off my hands and nearly removed some of the nails.
I don't thnk the major danger is the volitility, which based on hard starting may even be less than the old (real) "gasoline," but the (toxic?) fumes and danger to your hide.
With naptha/paint thinner/varsol you at least know what you are getting.
Unka' George [George McDuffee] ===========Merchants have no country. The mere spot they stand on does not constitute so strong an attachment as that from which they draw their gains.
Thomas Jefferson (1743-1826), U.S. president. Letter, 17 March 1814.
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F. George McDuffee wrote:

Aviation gas... They cant screw with that too much. The last time they did was when they went to 100LL. It doesn't leave a smell after it evaporates, just a little lead and it takes the oils out o your skin.
John
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