How To Clean Coins That Have Been In Saltwater
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Posted 01/18/2010 11:10 am 
I need some advice on cleaning some super dirty coins. I got a metal detector for Christmas and have been having a blast hunting for coins and other valuables. What I've quickly discovered is that coins in the ground for a while can get REALLY covered with grime. While I'm not too concerned about filthy modern clad coins, I know I'll start finding potentially valuable coins soon and want to be prepared to handle them properly.
While the general mantra is "don't clean coins", these things are all but unrecognizable in their current condition and I'm sure no one would want them as is.
On some metal detecting forums I've been horrified to read their suggested cleaning methods as they revolve around the use of vinegar and abrasive cleaning methods! They seem to think making the coin shiny as possible is ideal. The worst case I saw was someone that found a 1870 CC quarter that had only a tiny spot of grime and he was planning on giving it a vinegar dip before selling it on Ebay. But most of what I see here on this forum seems to assume the coin is a little dirty, not black as night and encrusted in 50+ years of grime.
I'm not expecting it to go from that to MS-63, I just want to do what I can to improve the condition of the coin without destroying the value by over cleaning it. Could anyone give me advice on this?
Thanks!
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Posted 01/18/2010 11:24 am
I'm a fan, especially with dug coins, of the freeze/thaw method. It involves repeatedly freezing and thawing the coin in distilled water; each cycle helps to break grime off the surface and no chemical or tool ever touches the coin. Of course, it only works for dirt/crud; everything you'd want acetone for is unaffected.
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Posted 01/18/2010 11:38 am
Ah, I didn't think about that in regards to silver. I've only pulled up clad coins and copper pennies so far and it is the pennies that have really been a disaster. Sounds like standard cleaning methods will work on everything but copper. I guess it won't be such a big problem unless I pull up some old cent that might be worth something.
Freeze thaw method is a new one to me, but it makes sense!
Edited by Saruma
01/18/2010 11:40 am
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Posted 01/18/2010 1:15 pm
what is the freeze thaw method and what does it do?
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Posted 01/19/2010 10:38 am
The so called freezze/thaw method is you place the coin in distilled water, then freeze, then thaw. The dirt is supposed to join with the water and just pop off as the ice melts off. Not always working as so many state. Sort of like the hundreds of other methods posted by people that have read it and have no idea if it works or not.
If you do searches on cleaning you'll read how great some things work such as lighter fluid, Alcohol, Pain thinners, Acetone, Vinegar, Lamp oil, Olive Oils, Lava Soap, Brillo Pads, Battery Acid, NitroGlycerine and many, many others.
The Nitro method works similar to dynomite. Not only gets the dirt off but gets rid of the coin as well. No more cleaning problems.
Back to your question. First of all a lot of that dirt may be in fact dirt. Try just soaking in Warm Distilled Water. If only dirt, most will come off. If that fails, try using Acetone. Read up carefully how to use it by searching this forum for Acetone.
Anything past that is probably to late for reconstruction of those coins.
A really big problem for Copper in the ground is the area where you find anything of Copper. In many areas where Sulfur Rich Coal is or has been used, the air becomes rich in SO or SO2. This mixes with the humidity in the air and comes down as what is termed Acid Rain. The now Acidic moisture enters the ground and attackes Copper to form CuSO3 or CuSO4. In many areas the Copper Grounding systems have been eaten away completely by this situation. In Illnois and Indiana, power stations have gone to using Lead Covered Copper for Grounding partially due to this problem.
just carl
Valued Member
United States
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Posted 01/19/2010 11:10 am
I metal detect also and I like the freeze/thaw method too! Acetone and a good rinse works also, but I dislike using a chemical on coins. I do have to say that I have yet to find a coin detecting (deeper than an inch) that is without serious problems. I hope that changes!
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Posted 01/19/2010 11:16 am
Thanks Just Carl, that was very informative. As for location of the cents, I live right by the beach in California. So these poor things have been subjected to salt water for who knows how long. What I'm finding is that the coins that suffer the most are modern cents. The copper plating tends to peal away from the zinc core, or the zing starts to pucker and makes the cent bumpy. Luckily there aren't really any valuable zincolns outside of a few error coins.
What really got me excited, then disappointed, the first few times were the quarters. Apparently if a clad quarter has been in the sand and salt long enough the nickel coating wears off and the coin becomes brown. I was SURE I'd found a 2 cent piece when I first started pulling them out of the ground!
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Posted 01/21/2010 09:37 am
Quote:
Thanks Just Carl, that was very informative. As for location of the cents, I live right by the beach in California. So these poor things have been subjected to salt water for who knows how long. What I'm finding is that the coins that suffer the most are modern cents. The copper plating tends to peal away from the zinc core, or the zing starts to pucker and makes the cent bumpy. Luckily there aren't really any valuable zincolns outside of a few error coins.
Salt water really does a number on coins. And usually not reversable. As to really nothing valuable in those, check out the prices of the error ones and the large/small date types. Many other types and varieties are popping up more and more as the number of collectors increases.
just carl
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Posted 01/21/2010 6:53 pm
I know some error modern cents are worth a lot, but when dealing with coins in the condition I often find them in I'm happy that relatively few fall into that category. Zincolns in salt water for any length of time start to get a separation of the copper coating from the zinc core, and many are so trashed that I'm not even sure I could spend them anymore.
I think my approach to the silver coins I find at the beach will be to use the proper cleaning methods as much as possible. But if they are still badly corroded after doing that I may try harsher methods under the concept that a "improperly" cleaned coin that is recognizable is better than one so corroded that is is all but unrecognizable. Don't worry, I won't take that step lightly, especially if I get a key or semi-key date, and I may post a picture here for suggestions first.
By the way, I found my first older coin yesterday. A 1929 SLQ. Under the corrosion and stuck on sand it looks to be probably in G-4 condition. So it will make a good first test subject with Acetone since it is only worth a few bucks anyway.
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How To Clean Coins That Have Been In Saltwater
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