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Techniques for CollectorsCleaning tar from rocks

9th Dec 2017 00:02 UTCAndy Young

Hi, I recently picked up some agates roadside and they are covered with little black dots that I assume are tar/asphalt. These spots scratch off with a dental pick, but are so numerous I would rather try a solvent of some kind. Any tips on a cleaning solution for this material? Thanks.

9th Dec 2017 00:08 UTCJolyon Ralph Founder

any organic solvent should do

9th Dec 2017 00:08 UTCJolyon Ralph Founder

try white spirits

9th Dec 2017 00:21 UTCAlfredo Petrov Manager

I know California collectors who use gasoline for cleaning tar off of tar pit fossils - Not very safe or healthy work.

If an organic solvent doesn't work, you might want to make sure those black spots aren't a manganese oxide.

9th Dec 2017 01:22 UTCPaul Brandes 🌟 Manager

Could you possibly put these in a basket and hit them with a pressure washer using warm water?

What about an ultrasonic cleaner?

Just throwing a couple alternatives out there......

9th Dec 2017 01:42 UTCDoug Daniels

There's also Goo-gone, a bit safer than gasoline. Maybe paint thinner, mineral spirits, acetone (a small bottle of nail polish remover). Lotsa good stuff to try.

9th Dec 2017 02:16 UTCReiner Mielke Expert

Diesel fuel will work. It's cheap and not very flammable.

9th Dec 2017 19:47 UTCJohn Oostenryk

I've messed with both road tar and bitumin/oil from in situ sources...

Some are more resilient than others...

Do a single piece first to see how it goes!

Smooth surfaces of course clean easier than rough, cracked, or porous, but I have worked with all of those and seen improvement.

Keep in mind that a solvent will wick/seep into all cracks/porous areas. It will also migrate the tar. Don't get too hung up on that detail though. The clean fluid will be entering sooner (than the dirty fluid), and will block the flow to some degree.

Some ideas to keep in mind on containment.

DO use a sealed or a "doubled" container to prevent evaporation of solvent. It will also help mitigate fumes depending on where you proceed at.

Depends on size of specimens of course, and how aggressive the solvent is versus plastic. Some plastics are unaffected by some solvents, or slowly.

Doubled = I have set a (sealable)food grade container with the solvent/rock (inside a glass/metal bowl-in case it melted (it did not)) inside a freezer ziploc bag or garbage bag.

I have used the ziploc bags to encapsulate a glass dish with rock at bottom, with a plate set flushly on top (to slow the evap on acetone).

Ideal is a glass jar with screw on lid that has interior white sprayed on coating. The cardboard interior type is not greatest but ok.

I have messed with teflon tape too (like pipefitting) for lip of jar too when no gasket.

For solvents- I have used the following things at times.

Best ever- but expensive~ is spray can- Brake cleaner (The flammable version!) Cost keeps me from using first though!~

I usually go with:

WD-40 (lube/solvent) oily but DOES evaporate clean without issues after couple weeks. Does have an odor for a bit(I don't mind it but some people do.)

Acetone

Lacquer thinner

Mineral spirits (NOT mineral oil :)-

Gasoline-- Works great but I hate the long lingering odor AND it is the worst to contain vapor wise, so IMHO-ONLY do that one outside (not in garage etc.

Gasoline stink can be mitigated by using other solvents after. I forget what combinations I used in past.

Others I have tinkered with...

White gas (Coleman fuel)

Naptha (charcoal grill lighter fluid)

Obviously- most of these burn- and the vapor is very flammable!

Safety awareness--Do not utilize soaking indoors NOR where there is a natural gas furnace, stove, or water heater, electric room heater or toaster, tobacco smokers, cats with candles, or naughty children with matches or errant fireworks...

Tha's plenty of detail!

Best Regards!

~JO:)

9th Dec 2017 22:05 UTCHoward Heitner

Mechanics hand soap might work. Leave it on for a while to soften the tar and then wash it off with water. It can be purchased in an auto supply store. I have also used a mixture of vegetable oil and liquid dish detergent to remove tree resin from the bottom of shoes. It has to be left on to soften the resin before being washed off.

10th Dec 2017 02:56 UTCNelse Miller

I have had good results using xylene purchased from a home improvement store. It evaporates and leaves no lingering odor. Treat it as carefully as you would any organic solvent.

10th Dec 2017 14:01 UTCHarold Moritz 🌟 Expert

Hexane is the best! We used it to decontaminate equipment in the environmental sampling bizz, dries fast and clean. Put it in a small plastic spray bottle, spritz on the rock and watch the tar melt away. Use outdoors and wear nitrile gloves and eye protection. Probably difficult to get tho. BTW, WD-40 is a water displacer, not a lubricant or solvent.

10th Dec 2017 20:21 UTCAndy Young

Awesome , thanks all for the knowledge!

10th Jun 2019 18:44 UTCSara Abel

I soaked mine in some Vinegar and that seemed to make it easier to scrape stuff off

11th Jun 2019 12:29 UTCEd Clopton 🌟 Expert

A medical method for removing tar from burn wounds (i.e. from getting splashed with hot tar) is mayonnaise, which stays in place without running off, or olive/vegetable oil. It's not fast, but it works at room temperature, is easy on the skin, and is safe indoors. I used one or the other (don't recall which) to clean bitumen off of a Sicilian sulfur crystal with good results.

11th Jun 2019 15:29 UTCJohn Truax

Wood ash (dry) and friction can remove road tar surprisingly well.

11th Jun 2019 19:50 UTCPaul Brandes 🌟 Manager

So does "goo-be-gone", and it has a nice citrus smell.... ;-)

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