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Removal of black gunk off silver
- Thread starter Bilko
- Start date
E-Trac-Ohio
Well-known member
Found a Mercury Dime that was heavily coated in what looked like- black road Tar.
I used an Electrolysis bath to clean it up.
Gasoline or Tar Remover from any Auto Parts Store will dissolve Tar - but ...
Before using any chemicals that could possibly damage the coin - I would take it to a local coin shop and see what they think !
Good luck !
I used an Electrolysis bath to clean it up.
Gasoline or Tar Remover from any Auto Parts Store will dissolve Tar - but ...
Before using any chemicals that could possibly damage the coin - I would take it to a local coin shop and see what they think !
Good luck !
....don't use anything too harsh mate.
Try this....it worked for me on a James I half groat which was totally black. I didn't know what it was until cleaned.
Simply cut two slices of lemon. Get some baking foil...place a slice on the foil...place the coin on that slice. Squeeze some juice on the coin and place the second slice on top.
Wrap up the whole lot in the foil and place something heavy on top.
Check it after 24 hours and repeat as necessary.
The lemon will go green as it lifts the black off.
Then rinse under warm water.
Gaz.
Try this....it worked for me on a James I half groat which was totally black. I didn't know what it was until cleaned.
Simply cut two slices of lemon. Get some baking foil...place a slice on the foil...place the coin on that slice. Squeeze some juice on the coin and place the second slice on top.
Wrap up the whole lot in the foil and place something heavy on top.
Check it after 24 hours and repeat as necessary.
The lemon will go green as it lifts the black off.
Then rinse under warm water.
Gaz.
Fire 
will remove tar. LOLutahshovelhead
Active member
Ok Gaz but I suggest a pinch of salt on the lemon...shaken not stirred for find dinning pallets! 
Do not use lemon juice. You dont want to remove the patina that may have built up under the tar/sticky substance. That tar may have preserved the coin and it original luster. You need a soak in toluene or nail polish remover.
Come on guys this obvious, I can believe all the bad advice here.
Come on guys this obvious, I can believe all the bad advice here.
I prefer electrolosis!
LabradorBob
LabradorBob
Cleaning Silver Coins
If silver coins get exposed to air they will get after some time a brown or even black oxidized layer. This is caused by the small amount of sulphur that air contains.
By knowing this chemical reaction, we could all imagine that the only way to stop this process is preventing that the coin is surrounded by air. There are ways to seal it in or cover it with an acid free jelly but most collectors prefer to clean the coins.
Because most coins are exposed to air cleaning will be necessary after some time.
The cleaning of silver coins can be done by different methods and on this page we like to present to you this specific information and how this can be done safely.
Keep in mind that for some coins, like ancient roman coins it might be wise not to clean them totally as they look more authentic with a light (ancient looking) color change caused by this natural silver oxidation effect.
Method 1: Lemon Acid.
Put the coin in a lemon acid bath for some hours to maximum one day depending on the thickness of the oxidation layer to be removed from the coin. After this bath clean the coin carefully with soft brush, rinse it with water and dry it with soft paper.
The effect of this method can be improved by putting some small iron nails in the lemon acid bath. This will improve the chemical reduction of the lemon acid bath and a faster cleaning of the silver coin will occur.
If you use some small iron nails do not leave the silver coin longer in the lemon acid bath then 30 minutes maximum and use the procedure as described earlier.
Method 2: Acid Fluid.
If the silver coin you want to clean has only some small oxidation spots then you can clean then best with an acid fluid like warm vinegar or sour milk on a soft tissue or a raw potato cut in half and rub the coin with it.
After cleaning it rinse it well with water and dry the coin with a soft paper tissue.
If silver coins get exposed to air they will get after some time a brown or even black oxidized layer. This is caused by the small amount of sulphur that air contains.
By knowing this chemical reaction, we could all imagine that the only way to stop this process is preventing that the coin is surrounded by air. There are ways to seal it in or cover it with an acid free jelly but most collectors prefer to clean the coins.
Because most coins are exposed to air cleaning will be necessary after some time.
The cleaning of silver coins can be done by different methods and on this page we like to present to you this specific information and how this can be done safely.
Keep in mind that for some coins, like ancient roman coins it might be wise not to clean them totally as they look more authentic with a light (ancient looking) color change caused by this natural silver oxidation effect.
Method 1: Lemon Acid.
Put the coin in a lemon acid bath for some hours to maximum one day depending on the thickness of the oxidation layer to be removed from the coin. After this bath clean the coin carefully with soft brush, rinse it with water and dry it with soft paper.
The effect of this method can be improved by putting some small iron nails in the lemon acid bath. This will improve the chemical reduction of the lemon acid bath and a faster cleaning of the silver coin will occur.
If you use some small iron nails do not leave the silver coin longer in the lemon acid bath then 30 minutes maximum and use the procedure as described earlier.
Method 2: Acid Fluid.
If the silver coin you want to clean has only some small oxidation spots then you can clean then best with an acid fluid like warm vinegar or sour milk on a soft tissue or a raw potato cut in half and rub the coin with it.
After cleaning it rinse it well with water and dry the coin with a soft paper tissue.
Electrolysis lifts that black coating off easily of silver
I recommend only using a low powered unit ...like from a mobile phone cahrger and checking it every 15 minutes
High powered units can damage a coins surface
its not good for copper in my experience
BUT please make sure its not a valuable coin first or you will kick yourself
good luck
please show us a photo if you do clean it
T59
I recommend only using a low powered unit ...like from a mobile phone cahrger and checking it every 15 minutes
High powered units can damage a coins surface
its not good for copper in my experience
BUT please make sure its not a valuable coin first or you will kick yourself
good luck
please show us a photo if you do clean it
T59
OhioCoinHunter
New member
Electrolysis will soften up the black stuff, which may be silver oxide. Then you just carefully rub and wash the black off.
Here's a Seated Quarter before electrolysis.
It's a freshly dug 1876 I found last September.
Here it is after 5 minutes in the electro tank.
The black coating was rendered soft enough to remove.
This is a coin I will never sell. I'd rather have it look the way it does now after electrolysis.
Here's a Seated Quarter before electrolysis.
It's a freshly dug 1876 I found last September.
Here it is after 5 minutes in the electro tank.
The black coating was rendered soft enough to remove.
This is a coin I will never sell. I'd rather have it look the way it does now after electrolysis.
Gaz said:
Hey smarty.... He said "thick black gunk".... Does everyone see this? He didnt say encrustation, black oxide, or rust. He said "thick black gunk".
The second response in the thread also mentions a tar like substance, which many of us have found on old coins that where discarded or lost.
Toluene does not harm silver and is as inert to metallic objects as you can get. Finger nail polish also dissolves tar and does not affect toning.
Lemon juice will destroy toning.
So what you are saying is that he should quite possibly destroy any numismatic value that his coin has especially if it is in AU shape under the tar.
I am suggesting worse? You call me an idiot?
It sounds like you have to spend some more time educating yourself
Cleaning a coin with lemon juice will make it nice and shiny.......
Do you know what flow lines are? He should remove those with lemon juice?
OhioCoinHunter
New member
Back in the mid-1970's a friend of mine told me his grandfather found a gold coin in a field with a metal detector. We went to his grandfather's home to see the coin. It was a thick gold coin with symbols and writing we couldn't understand. We made a rubbing of the coin with a piece of paper and a pencil and took it to the library where we learned it was Spanish gold.
Here's how it relates to this thread. My friend's grandfather said the coin was coated with a thick black substance - like tar - when he found it. He didn't know what was under the tar, only that it was metal.
How did he get the black stuff off?
He took it to a jeweler and let him clean it. He did an excellent job. So that's another option. These days they have profession coin cleaning & grading services, like anacs. However I've heard they've ruined some valuable coins when cleaning them. I don't know what their methods are. However there's always an element of risk even when professionals clean coins.
Here's how it relates to this thread. My friend's grandfather said the coin was coated with a thick black substance - like tar - when he found it. He didn't know what was under the tar, only that it was metal.
How did he get the black stuff off?
He took it to a jeweler and let him clean it. He did an excellent job. So that's another option. These days they have profession coin cleaning & grading services, like anacs. However I've heard they've ruined some valuable coins when cleaning them. I don't know what their methods are. However there's always an element of risk even when professionals clean coins.
burlbark said:Gaz said:
Hey smarty.... He said "thick black gunk".... Does everyone see this? He didnt say encrustation, black oxide, or rust. He said "thick black gunk".
The second response in the thread also mentions a tar like substance, which many of us have found on old coins that where discarded or lost.
Toluene does not harm silver and is as inert to metallic objects as you can get. Finger nail polish also dissolves tar and does not affect toning.
Lemon juice will destroy toning.
So what you are saying is that he should quite possibly destroy any numismatic value that his coin has especially if it is in AU shape under the tar.
I am suggesting worse? You call me an idiot?
It sounds like you have to spend some more time educating yourself
Cleaning a coin with lemon juice will make it nice and shiny.......
Do you know what flow lines are? He should remove those with lemon juice?
.....so.....are you going to have a go at the other forum members on here that have taken the trouble to reply??
Are you going to slate the people also suggesting lemon juice treatment to slowly loosen crud?....or the people suggesting electrolysis which is more harsh if not constantly watched minute by minute???
We'll have to agree to disagree before this thread gets out of hand and the mods step in..........agree?
Gaz.
Gaz said:burlbark said:Gaz said:
Hey smarty.... He said "thick black gunk".... Does everyone see this? He didnt say encrustation, black oxide, or rust. He said "thick black gunk".
The second response in the thread also mentions a tar like substance, which many of us have found on old coins that where discarded or lost.
Toluene does not harm silver and is as inert to metallic objects as you can get. Finger nail polish also dissolves tar and does not affect toning.
Lemon juice will destroy toning.
So what you are saying is that he should quite possibly destroy any numismatic value that his coin has especially if it is in AU shape under the tar.
I am suggesting worse? You call me an idiot?
It sounds like you have to spend some more time educating yourself
Cleaning a coin with lemon juice will make it nice and shiny.......
Do you know what flow lines are? He should remove those with lemon juice?
.....so.....are you going to have a go at the other forum members on here that have taken the trouble to reply??
Are you going to slate the people also suggesting lemon juice treatment to slowly loosen crud?....or the people suggesting electrolysis which is more harsh if not constantly watched minute by minute???
We'll have to agree to disagree before this thread gets out of hand and the mods step in..........agree?
Gaz.
I will take that as an apology.
Tar for one is an insulator and would still cling to the coin through electrolysis. It becomes hardened and crumbly. Only the spots exposed to solution would receive treatment causing spots and worse, pitting.