How To Remove Hard Green Crust From Coins?

[Jarl]

Hello,

A lot of the older coins I find have the classic 'green' crust on them, sometimes it is easy to remove with just water and maybe soap, but other times it is hard as cement. How do you remove that without destroying the patina of a decent coin? I know that hard mineralization in some cases can be removed by vinegar or some other acid...I have done it with success, but, that removes the deep tone luster that some coins have when they come out of the ground. Sometimes the green crust is really hard to budge and it partially covers the date of a coin. This is irritating. I have a few I am working on now, but all I feel safe using is peroxide...however, peroxide removes a lot of dirt well, but it isn't aggressive enough...without being too aggressive at the same time. I need a way to get rid of that hard green crust without altering the overall appearance of the coin(s). I was considering electrolysis but I think that would remove too much as well. What I used to do, and now I am trying to get away from doing, is something I read that archeologists do to clear matrix from fossils...they use a stylus point and press on the edge of the matrix to be removed until it 'snaps', then you wash or brush away the flakes. I did this with several of my green encrusted coins but later I realized that I was putting nicks on the coins themselves...these were not visible at first for some reason(I was using a loupe too). I suppose it could work maybe if your stylus wasn't too sharply pointed. Anyway, I knew that the coins I did this on were not valuable...only to me and my collection, but it worked well to uncover some dates.

Any advice appreciated! Thanks!

 

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[DianaPrince]

I'm interested in this as well.
I've only found two coins & neither of them are valuable beyond their normal US currency rate (1 Dime & 1 Penny so far) but the dime I found was crusted green & the penny has a good amount of hard packed dirt on it. I don't want to damage my coins. I'm actually glad that I found lesser valued coins first because they're going to give me something safe to practice on!
If there's anything that I've learned from joining this site, & I've really learned quite a bit, it's that you can easily destroy the value of your find with out researching how to properly & safely remove dirt & sediment from your finds.

 

[Prairie Prowler]

Sad part is the crust is the actual finish /patina that's leeched /oxidized off the coin over the years buried /exposed to the elements.. when cleaned its usually stripped of the actual coins metal..

 

[airscapes]

I am NO EXPERT, but just last night found a 1901 IH penny in my pile of clad while getting it ready to be tumbled. It was so crusted with dirt, it was like concrete and would not come off. I checked the value of the coin, in fair condition it is worth about $1..
So I searched the Tnet forum for cleaning and found the process of heating Hydrogen Peroxide and soaking the penny. Then you scratch at the custy with a tooth pick... repeat.. repeat.. repeat.. Getting there, but I must have hit the coin digging it up as there is one spot where the dark patina is rubbed off.. If the coin is a valuable year, you do not want to clean it unless you know what you are doing.. if it is just for your personal viewing and show an tell there are many methods posted in the cleaning forum for all different types of coin..

 

[DixieLandMan]

I found a wheatie and it had a lot of crud on it too. It was dated 1946 but I used lemon juice for about 30 minutes-1 hour and that worked well for me. got rid of a lot of the crud but I don't think it damaged the coin.

 

[Boatlode]

Swimming pool acid works on copper coins.

 

[huntsman53]

Acetone bath, rinse with fresh water, then soak in Mineral Oil or Extra Virgin Olive Oil for several days up to several weeks. Once removed with oil still on the coin, it is possible that most or all of the encrustation will likely come off with a light rub of a finger tip but for harder stuff, dirt and grime, use a green Rose Thorn on Copper coins only (as they will not scratch of damage Copper coins), not on Silver coins. There is not much you can use on Silver to aid in the removal of the encrustation except the Acetone and Mineral Oil or Extra Virgina Olive Oil as brushes, toothpicks, green Rose Thorns, etc. will scratch, gouge and damage Silver coins.


Frank

 

[airscapes]

I did not take a photo of the before... but it was like a penny sized piece or concrete.. after hours of hot Hydrogen peroxide and a lot of toothpicks, you can see all the detail that is left after 113 years.. Not worth anything in good condition so figured what could hurt cleaning it so I have somthing to show.. Oooo Ahhhhh .. till I find something better!

 

[bigfoot1]

pop it in a sealed small tupperware container with pepsi....chek every hour.never for key date stuff tho.

 

[Jarl]

Thanks for all the suggestions, everyone. It is really appreciated!

 

[Silver Searcher]

It's no good asking about cleaning copper coins with out knowing what is to clean(pictures) ask yourself this....what is it going to be like when I remove the green crust, which by the way is corrosion, just like removing rust from iron, the detail has already gone. eaten away. Patina is just basically rust, some times it's stable and you can seal it to keep it that way. When you remove a coin from the ground and expose it to the air corrosion has already started, I usually place a coin in a sellable bag with the damp earth.

The most damaging corrosion occurs when chlorides and moisture come into contact with a coin, and chlorides are unfortunately quite common in the ground. The copper and chlorides react to form cuprous chloride, which causes progressive corrosion in the presence of moisture. It leaves the surface with patches of pale green, powdery material. This is commonly referred to as bronze disease and must be taken care of by removing the chlorides before the whole coin eventually disintegrates.

Do not use tap water. The chemicals in tap water could actually increase the corrosion. Soak in distilled water. This may seem to be counter-intuitive since moisture is needed to start the reaction in the first place, but it does work. Using a magnifying glass and a sharp needle to remove any obvious green spots still visible. Over a period of time, distilled water will attract the chloride ions. As the water becomes saturated with chloride ions, the effectiveness will be reduced. Change the water periodically, every two or three days at least.

Always try and find out the value of any coin you are cleaning first, some times there's know way of telling with badly corroded coins, these will usually be worthless anyway, but always take care, if you don't know ask...better to be safe than sorry.

SS

 

[BamaBill]

Would electrolysis work with a copper coin?

 

[Silver Searcher]

Would electrolysis work with a copper coin?

It's not a good option, but you can do short bursts. I have done roman coins this way, that were very bad, but usually it leaves pitting on the coin.

SS

 

[prospect007]

has anyone tried an ultra-sonic cleaner with jewelry cleaning solution?