Author Topic: Which cleaning agent?  (Read 539 times)

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Offline idiotghost

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Which cleaning agent?
« on: May 05, 2019, 02:00:46 PM »
Amateur question: Which are the best liquids (or whatever) that can be used to clean old coins? I have a whole range of metal coins, especially bronze & old silver coins (turned black due to oxidation). If someone can elaborate on what liquid to use best corresponding to what metal composition, it would be excellent for me for cleaning. Bronze & silver ones are the first that I'm gonna clean..

Offline Arminius

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Re: Which cleaning agent?
« Reply #1 on: May 05, 2019, 02:25:59 PM »
Amateur question: Which are the best liquids (or whatever) that can be used to clean old coins? I have a whole range of metal coins, especially bronze & old silver coins (turned black due to oxidation). If someone can elaborate on what liquid to use best corresponding to what metal composition, it would be excellent for me for cleaning. Bronze & silver ones are the first that I'm gonna clean..

These kind of questions make no sense as every metal alloy, every patina, every expected result and every dirt is different.
So there will be no best solution / liquid / method in general.

The only way to learn is the uncomfortable and time consuming way to get your own experience. This can be only be supported a little bit by online discussions and general recommendations.

You will find a lot of cleaning discussions here and elsewhere. But it´s like your parents recommendations to find the ideal partner. Without own experience ....

regards

Offline Figleaf

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Re: Which cleaning agent?
« Reply #2 on: May 05, 2019, 02:36:49 PM »
Unfortunately, it's not an absolute science. It depends on your taste and how badly the coin is affected. Other people's taste becomes important if at some time you expect to be selling the coin.

To give you at least something to chew on, here's my personal approach: in principle, don't clean. Nature has a way of dealing with metal that makes it better. There are exceptions to the principle (aren't there always?)
  • The coin is affected by bronze disease or another problem that will eventually destroy it. In such cases, anything is allowed. Just try to spare as much metal as possible.
  • There's foreign muck on the coin that covers an important detail. Remove the muck, but at least try not to affect the patina.
  • The coin looks plain ugly. Ah, but will it look better when you clean it? If so and there's little or no risk, well, it's your coin. Take into consideration that if the coin is scarce, it's not all yours. It also belongs to future generations.
For more details, look at Reply #6. Ask more questions. Practice on cheap coins first. Good luck.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline gpimper

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Re: Which cleaning agent?
« Reply #3 on: May 06, 2019, 04:41:06 AM »
Peter and Arminius,  well said.  We've been working through all types and it really is hit and miss at first.  Catie had a stack of bronze (five Roman coins all stuck together) that we were trying to work but had to just let it stay, well, a stack of bronze Roman coins (pretty cool, actually).  The only coins we try to clean are the crusty and ones that we think we could get better detail...doesn't always work out :-(  Softer is better and it takes time.  Certainly a leaning experience!
« Last Edit: May 06, 2019, 05:29:27 AM by gpimper »
The Chief...aka Greg

Offline Figleaf

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Re: Which cleaning agent?
« Reply #4 on: May 06, 2019, 07:07:57 AM »
I seldom got to see stacks like that. They were usually silver and coming out of ship wrecks. One archeologist told me he would treat them to repeated ultrasound sessions. Personally, I use ultrasound mostly for proofs and uncs.

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline bruce61813

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Re: Which cleaning agent?
« Reply #5 on: January 12, 2020, 06:56:38 PM »
I would try low-voltage [6 VDC or so]  electrolysis using a baking soda - washing soda mix. It is a slow process but will do minimal damage. You can't avoid some damage, but the layers should separate. This is used to stabilize metal items that have been in seawater for extended periods of time.

Bruce

Offline Figleaf

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Re: Which cleaning agent?
« Reply #6 on: January 12, 2020, 07:42:21 PM »
Thank you, Bruce. None of us can be sure we'll never have to use this method. How long should a session be, before you take it out, give it a rest and resume later?

Peter
An unidentified coin is a piece of metal. An identified coin is a piece of history.

Offline bruce61813

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Re: Which cleaning agent?
« Reply #7 on: January 13, 2020, 02:30:33 AM »
Using low voltage DC gives you a lot of control, especially using soda mix. Note: NEVER use salt, NaCl, it will destroy the coins. I would try 10 minutes, the outer surface will probably turn black and look fuzzy. Take the coin mass out and lightly scrub it with a still toothbrush. Then start the second session, repeat as necessary. 10 minutes may not be long enough, just watch it and stop when you want, remember to scrub between sessions.

Bruce

Offline gpimper

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Re: Which cleaning agent?
« Reply #8 on: January 13, 2020, 11:58:05 PM »
Glass cup, old spoon, two cables with alligator clips, 6 volt battery, distilled water.  Fill the cup about 2/3s put the spoon in.  Attach the negative to the spoon and the positive the coin (I think, could be backward on that :-)  Submerge the coin.  If it starts to bubble you've got it right.  Just don't over do it...I've killed some really neat coins :-(  It'll clean all of the crusty stuff fairly quickly (5-10 minutes).  Soft soap and hot water and repeat as necessary.  Hope that was helpful. 
Bruce, correct, NEVER use salt!  Olive oil works pretty well.  I pretty much just stick with basics anymore. 
The Chief...aka Greg

Offline bruce61813

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Re: Which cleaning agent?
« Reply #9 on: January 14, 2020, 04:08:34 AM »
Add a teaspoon of baking soda and a teaspoon of sodium bicarbonate [if handy] to the above. Slows the conduction a bit and will help neutralize any bronze disease. I use a 6 VDC charger from an old cellphone. Cheaper than a battery. Reminder - Do Not add salt, NaCl, to the water.

Bruce

Offline gpimper

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Re: Which cleaning agent?
« Reply #10 on: January 14, 2020, 08:24:08 AM »
Add a teaspoon of baking soda and a teaspoon of sodium bicarbonate...I'll have to try that!
The Chief...aka Greg

Offline bruce61813

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Re: Which cleaning agent?
« Reply #11 on: January 14, 2020, 02:35:23 PM »
The soda/bicarbonate of soda mix is an effective treatment of Bronze disease.  I have used it for a number of years, and it's use goes back to the 1930's and museum conservation of copper-based alloys.
Here is the link to a paper: Cupreous Metal (Copper, Bronze, Brass) Conservation - Conservation Manual -] [url=https://nautarch.tamu.edu/CRL/conservationmanual/File12.htm]Cupreous Metal (Copper, Bronze, Brass) Conservation - Conservation Manual -. My short summary of the Treatment of BD is based on this and a couple of other works.


Bruce
« Last Edit: January 14, 2020, 02:50:26 PM by bruce61813 »