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Techniques for CollectorsNon-oxidative removal of organic crud

27th May 2016 21:49 UTCHenry Barwood

I usually soak specimens that have organic films and other grunge on them in Hydrogen Peroxide solution. This is very effective, BUT it oxidizes pyrite and produces other problems with Fe sulfate and oxide residues as well as destroying the pyrite.

Does anyone know of a non-oxidative method to remove organics from specimens? Any help appreciated.

27th May 2016 23:34 UTCAlfredo Petrov Manager

I use caustic soda solution. There are a few minerals that you wouldn't want to use that on (realgar, orpiment, vivianite, scorodite, and several others), but it works fast on most species without damaging them. Nowadays KOH is more easily available than NaOH and should be just as effective. Ammonia solutions supposedly work too on many organic cruds, although I haven't used it myself; don't like the smell.

27th May 2016 23:36 UTCHenry Barwood

Any idea how caustics would work on syenite minerals? I've used caustic solutions to clean silicates, but not zeolites and feldspathoids.

28th May 2016 00:24 UTCBrander Robinson

How about the enzyme pepsin-never tried it but seems safe. Depends on the organic substance in the crud also.

28th May 2016 00:51 UTCHenry Barwood

Any idea of the cost of pepsin, or availability?

28th May 2016 02:01 UTCPeter Tarassoff Expert

I have had good success by soaking minerals for 12-24 hours in water to which I've added a few cc of sodium hypochlorite in the form of household/laundry bleach. I follow this by a soaking in water to remove residual bleach. I always do this before using an "iron-out" product.

28th May 2016 02:56 UTCHenry Barwood

I've also used commercial bleach, but like H2O2 it oxidizes pyrite

28th May 2016 03:02 UTCBrander Robinson

Henry- I got it from Spectrum Chemical some years ago. They have a 800 # that you can call for prices. I was buying pharmaceutical grade and it was expensive. I may have some left that will never use if I can find it but may have lost some potency over the years if you want it. It was used to remove egg stains from US Park Service statues in DC since acids and bleach damaged the marble and other materials. I suggested it and was told it worked for egg stains.

28th May 2016 03:06 UTCHenry Barwood

Brander, I'll ask our organic chemists if we have any in the stockroom. I would like to at least try it to see if it will work without degrading the specimens.

28th May 2016 05:19 UTCSteve Hardinger 🌟 Expert

I have my doubts that pepsin would be a useful general tool to clean organics from minerals.

Pepsin is a protease (an enzyme that breaks down proteins). See: https://en.wikipedia.org/wiki/Pepsin. I doubt is has wide activity to degrade other organics, and I doubt most 'organic mineral crud' is proteinaceous. I'm not surprised it worked to remove egg residue, but would be quite (pleasantly) surprised if it removed generic organic crud such as bitumen, tobacco smoke residues, etc.

28th May 2016 06:03 UTCDoug Daniels

Well, just so you don't use Pepsi.......

28th May 2016 06:05 UTCAlfredo Petrov Manager

Pepsi (or Coke) is however excellent for cleaning native copper :-D

(and corroded car battery terminals)

28th May 2016 06:15 UTCDoug Daniels

Even better to drink, every so often

28th May 2016 06:24 UTCAlfredo Petrov Manager

I don't know, Doug, it's dissolving the apatite in your teeth :-D

28th May 2016 13:41 UTCHenry Barwood

Colas clean mostly because they are dilute phosphoric acid.

30th May 2016 20:51 UTCKen Doxsee

"Adolph's meat tenderizer", sold in the USA, contains a digestive enzyme. Lord knows if it would work on organic crud on minerals, but it would be a cheap alternative to pepsin, if someone wanted to try an experiment! --Ken

30th May 2016 21:52 UTCHenry Barwood

Ken, your post reminded me of Papaya juice. I think that Adolph's is the same enzyme in Papaya. Might be worth a try.

31st May 2016 19:29 UTCKen Doxsee

Adolph's used to contain papain (from papaya), but apparently they have switched to bromelain (from pineapple). --Ken

31st May 2016 19:37 UTCSteven Kuitems Expert

There are enzymatic waste line cleaners available but I do not know about there effect on mineral specimens. Might be worth experimenting with.

Steve,

31st May 2016 21:00 UTCŁukasz Kruszewski Expert

Never though about exotic fruits and mineral cleaning... That's a new thing to me ;-)

1st Jun 2016 09:57 UTCTimothy Greenland

It's worth mentioning perhaps that enzymes will work on specific substrates. Meat tenderisers (and papaya juice etc) will degrade proteins. Others can degrade carbohydrates or lipids etc. They will not work or other substrates. There are enzymes used by some exotic bacteria that degrade hydrocarbons and the like, but I have no idea if they are available to the general public. I have generally found that a good soak in acetone in a sealed container in a cool place outdoors (out of the sun) is the most effective and not damaging to the underlying specimen in most cases. If the 'crud' is severely hydrophobic and resists, a first treatment with a light hydrocarbon preparation like lighter fuel followed by an acetone rinse or two before copious washing with water may be useful. Careful of the fumes - and NO SMOKING!

Cheers

Tim

26th Aug 2016 21:37 UTCJonelle DeFelice

Hmmm... someone mentioned Pepsi...

I think it was Mythbusters who showed what happens to a steak left in a container of soda overnight. The result was rather nasty.

Could soda of various types (and flavors!) be used on anything other than copper? I assume it is still an acid, so would it be bad for some minerals? Or is it way too diluted to worry about?

26th Aug 2016 22:23 UTCBob Harman

JONELLE, If you want to be taken seriously as a mineral collector you don't use soda pop as an acid or cleaning fluid. Water.....fine. Vinegar as a weak acid.....fine. Other acids for specific jobs.....fine. Bleach as an organic remover.....fine. Baking soda in solution for neutralizing residual acids.....fine. But soft drinks, beer and wine, and other food and drinks, basically no way. CHEERS.....BOB

26th Aug 2016 22:41 UTCJonelle DeFelice

Weeeell, they are liquids with similar chemistry! ;-) Just trying to insert some levity into life...

26th Aug 2016 22:53 UTCThomas Lühr Expert

Hello Jonelle,

No, soda (washing soda, Na2CO3) is not an acid. It is the opposite from an acid, it's an alcaline substance (a base). But you are right, both acids and bases can be aggressive to minerals, depending of their composition. So I would not treat any secondary lead or zinc mineral with soda, just to say an example.

On the other hand, bases (caustic soda, NaOH) can be used to remove crusts of secondary minerals (anglesite/cerussite or antimony ochre) from galena, stibnite etc.

Organic stuff on chemically and/or mechanically not robust minerals IS a problem. Dishwasher tabs or dental cleaner (for false tooth) give SOMETIMES (and with much patience) good results. They contain encymes to decompose organics.

Thomas

27th Aug 2016 03:41 UTCAlfredo Petrov Manager

Why criticize someone for using a drink as a mineral cleaning fluid? I will proudly stand up and admit I've used coca cola for cleaning some mineral specimens. The phosphoric and citric acids, combined with the mechanical agitation of the bubbles.... beautiful job. Well, perhaps I would not call it a "drink" as I don't think it's fit for human consumption, but it's great for cleaning minerals, and corroded car battery terminals...

I've used other citric-acid-containing drinks in a pinch, when the pure acid wasn't available, to prevent yellowing after dissolving limonite in HCl.

:-D

27th Aug 2016 15:11 UTCJonelle DeFelice

To clarify, by "soda" I don't mean bicarbonate. I mean citric acid in drinks like Pepsi, Coke, etc. There is a reason the stuff isn't suggested for people with acid-reflux!

27th Aug 2016 15:47 UTCKelly Nash 🌟 Expert

Henry, just FYI, pepsin is available via Amazon.com. There are probably cheaper places to get it, but I have been surprised how many chemicals are available there.

27th Aug 2016 17:15 UTCD Mike Reinke

This is maybe a long shot, but I just had my carpets cleaned yesterday and they pre-spray with an 'enzyme'. Might that help?

27th Aug 2016 17:36 UTCAndrew Debnam 🌟

I have had good success with removing "crud" removal using Fantastic with bleach. Spray it on then scrub with a brush and rinse thoroughly.

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