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Techniques for CollectorsHow to clean native silver?

19th Jan 2006 10:25 UTCFederico Perola

Does anybody know how to clean native silver on calcite without damaging the specimen?

26th Jan 2006 02:02 UTCDavid Aldridge

Try putting about 1/2 cup of baking soda into 2 cups of water. Next, cover the bottom of a pot with aluminum foil. add water and boil. Next, add the silver and several (at least 5) small 1-inch diameter balls of aluminum foil. Keep silver in boiling water for 10-15 minutes... Always works great for me!

26th Jan 2006 07:13 UTCFederico Perola

Thanks David!

As soon as it is possible I will try your method.

Another question : must I use distilled water?

27th Jan 2006 00:20 UTCDavid Aldridge

I find that distilled water works best. I HIGHLY RECCOMEND USING THIS TECHNIQUE ON A SMALL SACRAFICIAL PIECE OF THE SPECIMEN AT HAND. Although this method always works for me, It may not work to your satisfaction. If the sacraficial piece is not what you want it to be like, I'll try to think of another way.

27th Jan 2006 04:55 UTCRobert Meyer Manager

Hello,

I assume that you mean removing the tarnish, instead of simply cleaning soil from the specimen. The method I will outline is similar to that of David above; like his, it works electrolytically. You can use it to remove a good percentage of the tarnish on silver specimens and I don't think it will harm calcite. Best results are obtained by observing the specimen during treatment and pulling it out when enough tarnish has been removed to improve the appearence. Some tarnish can be quite aesthetic. You should also carefully consider whether the tarnish is actually unsightly before you risk a specimen. Try the treatment for a minute or two and then repeat until you are satisfied. It is best to err on the side of conservatism, rather than ruin a piece.

Here is the method: Place a flat piece of aluminum at the bottom of a sauce pan. A nice short length of aluminum flat bar is best, but any solid flat piece of aluminum will work. Fill the pan part way with enough distilled water to cover the specimen when it is resting on the aluminum. Create a saturated solution by heating up the water until it is warm to hot (not boiling) and adding baking soda (sodium bicarbonate) and table salt (sodium chloride) in equal amounts until you can dissolve no more. A little excess undissolved salt or soda does not seem to harm anything. Place the silver specimen on the aluminum so that the silver metal makes electrical contact with the aluminum. Wait and watch, keeping the solution below boiling in temperature.

This method has worked for me.

Best Regards,

Bob

30th Jan 2006 07:09 UTCFederico Perola

Yesterday I cleaned the two pieces of native silver that I have with the method of Bob but I did not add sodium chloride.

It worked very well, in about 2 minutes the tarnish go out without damaging the calcite and the two pieces were very good.

I thanks David and Bob for their help!

17th Feb 2006 20:43 UTCPaul Brandes 🌟 Manager

Federico,

If you can find it, a silver cleaner called "TarnX" works very well to clean silver and copper, without damaging the clacite or other minerals......

19th Feb 2006 07:34 UTCFranklin Roberts

You'd better watch out when using Tarn-X with calcite! The active ingredient in Tarn-X is acidified thiourea, a potent reducing agent. While thiourea is probably one of the best ways I know of to remove tarnish and corrosion from copper and silver, Tarn-X contains acids to lower the pH of the solution. These acids will rapidly attack carbonates such as calcite and malachite. I've used straight thiourea to clean copper and silver electronic parts with success. One of the more interesting cleaning methods I've tried involves placing the metal to be cleaned in a solution of thiourea and then adding an equal amount of 30% hydrogen peroxide. After a few seconds, the mixed solutions will react violently enough to spew boiling liquid out of the container. (This is best done outside, over a catch basin.) After the reaction quiets down, the metal will have acquired a mirror-like polish. This method is a variation of an old metal finisher's process known as bombing. The original process used sodium or potassium cyanide instead of the much safer thiourea. Definitely not recommended, even if you could get the cyanide. 30% hydrogen peroxide can be gotten at any Home Depot store, if you know what to look for. This stuff is extremely nasty and will leave painful bleached spots on any exposed skin it happens to contact.

Franklin Roberts

Austin, Texas

20th Feb 2006 14:35 UTCFederico Perola

I also thanks 'CaptPaul' and 'Franklin Roberts' for the suggestion but I cleaned the pieces of Native Silver with the method of 'Robert Meyer' and I am very satisfied of the result

Regards

Federico

21st Feb 2006 20:17 UTCMel Judy

Would either the electrolytic method involving the silver-aluminum cell or the use of "TarnX" be usable on a matrix specimen of native silver dendrites on native arsenic? The use of aluminum wads circulatinjg by boiling water might allow the former to work here.I would appreciate coments from users of both methods.

Thanks and Best Regards,

Mel Judy

5th Nov 2006 17:36 UTCDoug Mcdow

Bob, I found a 19.92 lb silver nugget in Az.. Not knowing better I tryed to clean it with mueratic acid. It didn't take the tarnish off. I hope I didn't ruin it. Do you think it is to late . Thanks Doug

4th May 2007 19:24 UTCIgnacio Gaspar

Hi!

Does the method explained by Robert Meyer works for cleaning pyrargyrite?

Thanks

Ignacio

5th May 2007 12:24 UTCAlfredo Petrov Manager

Ignacio, The electrolytic methods probably won't work on pyrargyrite because sulphosalts do not conduct electricity. The native slver works because of its conductivity.

16th Sep 2007 02:53 UTCRandy

Doug when you used the muratic acid did it turn a dark shade of gray?

16th Sep 2007 05:20 UTCCaleb Simkoff

warning on using tarn x on native silver!

some silvers become "addicted to it" and will tarnish more often after being treated just once!

beware!

14th Nov 2007 00:55 UTCRonald L. Blattman

Just a note for keeping silver specimens bright. Enclose it in a plastic or glass box with a piece of 3M Anti-Tarnish paper enclosed.

28th Apr 2012 06:03 UTCHunter

I metal detect on the weekends for fun and think I may have found a silver nugget but not sure so what's the beat way to tell.

28th Apr 2012 22:21 UTCRonald J. Pellar Expert

One consideration for the method of cleaning silver, it that the electrolytic aluminum technique reduces the tarnish depositing the silver back on the specimen. Other methods of tarnish removal actually removes the tarnish (silver sulfide) taking the combined silver with it . This means that repeated cleanings with non-electrolytic methods will gradually reduce the weight of silver in the specimen over time.

26th May 2012 05:29 UTCPeter Haas

Be careful with thiourea. This stuff is highly mutagenic.

21st Sep 2012 20:13 UTCAnonymous User

Have another question for this thread. Ran into some nice micro silver crystals in the Keweenaw of Michigan. Some are very sharp and lustrous in prehnite vugs but others were at or near the surface of the rock and look dull (tarnished?). Would appreciate recommendations on cleaning these crystals. Preserving calcite is not an issue (in fact I'm acid etching calcite off some of the trimmed rock fragments in attempt to discover more crystals, some of the vugs and fissues are calcite filled). However, a few silver cystals are associated with copper wires. Another potential problem in cleaning these specimens is loss of the crystals, some are loosely attached in the vugs. In fact one silver crystal disappeared during handling of the material (disappointing as that one had an associated tangle of copper wires!).

Thanks,

George

22nd Sep 2012 10:05 UTCRock Currier Expert

Hydrochloric acid, about 10% volume/volume from the concentrated HCl will remove the calcite nicely, but you will have to work it in and out of the solution to see where you stand with fine small crystals and wires that are sparse in the calcite. Otherwise you will likely end up with a lot of crumbs in the bottom of your etching solution. I don't think I am telling you something you don't already know or suspect.

22nd Sep 2012 12:21 UTCKeith A. Peregrine

George,

I have found using vinegar to do the trick as long as you soak the piece for just a minute or so. This has removed the tarnish on silver and most UP copper while barely touching the calcite. Only problem is that depending upon any impurities within the silver and copper which after rinsing and exposing to the air, the silver and copper may tarnish again. Usually, the silver will not tarnish but I've had a few pieces that do. As for the copper, most of it does tarnish as it dries.

22nd Sep 2012 17:10 UTCAnonymous User

Rock and Keith,

Thanks for the information. For this job the calcite is not an issue, am actually removing the calcite from

some of the fragments in hope to expose xls in more prehnite vugs. My etching acid of choice is vinegar

which seems to be gentle but slow. In other threads on mindat it has been mentioned that vinegar can etch

copper but have not noticed that. Sulfamic acid seems the consensus acid used by Copper Country collectors

and admit it is cheaper and faster especially if you have massive calcite but is the chemistry different such

that it will not etch copper?

No matter what acid is used I like to pay good attention to removing all the acid by repeated rinsing and

soaking in water, up to 4-5 water changes over a prolonged period. I have the impression some of the patina

lost due to acid treatment of copper returns with prolonged soaking.

One veteran Keweenaw collector tells me copper patina is not as strongly affected by acids if the copper has some

arsenic content. At least this seemed to hold true for Ojibway Mine copper etched with vinegar and soaked.

The result was not the new penny bright look but a soft darker patina.

Sorry, think I am wondering off topic and much of this is discussed in other threads.

George

22nd Sep 2012 23:14 UTCPaul Brandes 🌟 Manager

George,

What Rock mentioned is a good mixture for HCL as you don't want straight acid or even muriatic because it will etch/bubble calcite too vigorously and thus you will lose any small silvers you're trying to keep. Vinegar is a good choice and usually what I use if I have delicate specimens. I would imagine if you left a specimen in vinegar for weeks/months at a time you may have some etching, but I have never had an etching issue with just plain old household vinegar. If I just want to remove calcite from non-crystalised copper or silver, then I will use straight muriatic out of the jug. If you want to preserve any calcite such as calcite crystals on copper, then sulfamic is the way to go. Again, I would imagine if you left a specimen in sulfamic too long it will begin to etch, but I never leave them in long enough to find out.

As far as preserving the patina found on copper especially copper crystals, I won't use any acid as it will remove it and never return to its former beautiful self. An old trick I was told many eons ago was to rub your fingers on your nose or face and then rub the copper and it will take a shine without damaging the patina. I've tried this and it does seem to work, to an extent.

23rd Sep 2012 04:55 UTCJim Gawura

George,

I use sulfamic acid exclusively for cleaning copper and silver specimens. Learned about it from some Keweenaw locals. Even after soaking a specimen in it for a week there is no noticeable etching. It will attack all calcite vigorously and bubble and fume. It is usually sold in 50lb bags. It comes as a fine white crystal. Mix with water till the solution is saturated. It is mainly used to clean boiler tubes. I've used over 200lbs and it is the only acid I'll use on copper or silver. HCL and muratic even heavily diluted etch the copper and silver. As for patina even vinegar will remove it. My experience with reforming a patina on copper is mixed. Some pieces will dull up if left to soak in water and others stay shiny and bright. The arsenic may well be a big factor. Same results in air. A local collector, dealer in Da Yopper told me about the oil off the outside of your nose, works great!

23rd Sep 2012 04:59 UTCPeter Haas

A thin tarnish is easily removed with dishwashing liquids and gentle rubbing (though, onbviously not suited for delicate specimens). Dishwashing liquids contain a few tenths of a percent of certain additives (usually benzotriazine, tolutriazine or similar triazine derivatives) to prevent silver or silver-plated cutlery from tarnishing.

23rd Sep 2012 14:42 UTCAnonymous User

Once again thanks for the comments.

Paul, am a bit confused that you mention sulfamic acid could be used to preserve calcite crystals on copper. Perhaps you mean quartz crystals on copper? Expect that sulfamic would remove every bit of calcite, massive or crystals.

Agree that acids should not be used to clean copper unless you like shinny copper but if you are taking calcite off a copper crystal group contact with the acid is unavoidable.

Should also mention that although much attention is payed to metals in the Keweenaw acid etching with gentle acids is great for revealing crystals of other minerals such as prehnite, quartz, pumpellyite, feldspars <'adularia'> etc. Assume just about any mineral locked in calcite can be revealed but as I compose this message just had a thought. Recently ran into rocks with micro amounts of malachite and chrysocolla that are now in vinegar. As malachite is a carbonate is it likely to dissolve in acid, perhaps more so with stronger acids?

George

23rd Sep 2012 22:52 UTCKeith A. Peregrine

George,

Your remark about malachite and chrysocolla are well made. Acids will dissolve them. Though I have not attempted to remove malachite from a specimen, chrysocolla in the UP vanishes quickly since much (all I've ever seen actually) is only a coating on a sample.

Keith

23rd Sep 2012 23:38 UTCPaul Brandes 🌟 Manager

George Balogh Wrote:

-------------------------------------------------------

> Once again thanks for the comments.

>

> Paul, am a bit confused that you mention sulfamic

> acid could be used to preserve calcite crystals on

> copper. Perhaps you mean quartz crystals on

> copper? Expect that sulfamic would remove every

> bit of calcite, massive or crystals.

>

Warm sulfamic will dissolve carbonates pretty rapidly just as room temperature HCL, but cold sulfamic works very slowly. Again I never leave them in long enough to etch the calcite; never more than 20-30 seconds in which case I have never had an issue.

25th Sep 2012 04:37 UTCAnonymous User

Paul,

Now I understand, you were talking about cleaning not etching.

Keith,

Will have to check my samples once they have gone through some rinsing. The pieces with micro malachite and chrysocolla have sat in vinegar in the garage for 1-2 weeks and perhaps some will be etched off. Was trying to clear

away calcite in hope of revealing better malachite xls. Probably should have monitored this more closely. Will not know much until the pieces are under the microscope.

Other fragments did not have calcite and were not run through the vinegar. This includes some material that I assume is chrysocolla but not certain; transparent glassy light blue material forming thin casts around quartz crystals and one example of similar material forming glassy looking fine threads, like spun glass. Strange stuff but microscopic. Need to so some photography.

George

26th Aug 2014 01:05 UTCMikemannu

Does the electrolytic aluminum method work for copper as well???

24th Sep 2014 17:22 UTCReiner Mielke Expert

No.

12th Oct 2014 00:04 UTCAnonymous User

I tried the electrolysis method in a pan with cold water and aluminum foil. It didn't work very well. I went to the local camping store, and bought an aluminum boiler pot, then tried the process again with near-boiling water, and lots of bicarbonate and salt. Wow! What a difference. The silver cleaned up fast and nice.

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