HAPPY HOLIDAYS!! I am sure that this topic has been discussed many times, but as a newbie here I would appreciate some advice on coin cleaning. I know that coins should "never" be cleaned, but as these coins were badly green coloured - probably from having been in plastic - I felt that they were not very nice like this and perhaps there was not so much to lose. Therefore a small experiment - my first - with baking soda, aluminium foil and warm water. Just some 10-20 seconds in the bath and then I rinsed them off with (tap) water and dried them. The green is gone, but likely also a little of the silver? The two first pictures are before, and the two other are after the experiment. Now, is this something that is ruining the coins and should never be done, or is it "saving" the coins from the green guff that would otherwise just continue and eat away at the coins? Will the process continue or has it (the green stuff) been stopped? Will the "cleaning" process continue and should I stop it somehow? Will the environment now "attack" the surface of the coins as the protecting patina has been removed? Or has it been removed? There are so many here with so much knowledge, experience and opinions on this matter. Please comment so that we (at least I but hopefully also many others) can learn how to do and how not to do! Perhaps I will now receive a lot of comments on how stupid I have been to "clean" or having ruined these coins, but that´s OK! I am here to learn from the more experienced, so just throw them at me and I will learn from them. Thank you very much in advance! Let´s get the discussion going!
Far better to use pure acetone.......it won't harm the silver. I don't about getting the 'green stuff' off ,though. I've never tried it on coins in such a condition. The chemistry boys will tell you about the baking soda. @desertgem
Green is right just use acetone. As for baking soda and ash will remove the patina. It really depends on how you apply it & for how long. Used sparingly & briefly with no rubbing the patina should be fine.
OP, the good news is that it looks like these coins aren't super valuable collectible coins. The bad news is that baking soda and aluminum foil cause an electrochemical reaction on the silver. It has stripped any protective oxide/sulfide layer from the coins, so they may tone significantly in the near future. The green stuff looks like PVC residue, and, yes, it comes from being in holders of the wrong kind of plastic. The other "good" news here is that with the green being so far gone, the PVC had likely already damaged the surface of the coins, so there was little you could have done to hurt them in the first place. The proper way to conserve coins with PVC residue is to soak them in acetone. This dissolves the PVC and is completely safe for the coin, provided you don't rub the coin dry (just let it air dry).
I agree with the above posters to use acetone and never to use baking soda. I had a coin that had pretty bad pvc damage because I left it in the holder it was shipped in which was apparently pvc. I put a small bit of pure acetone I got on Amazon in a shot glass and let it soak (swirling the acetone around every so often). It took the better part of the night but it eventual worked. Every few hours it might help to take a Q-tip and ROLL it gently across the surface. Never scrub it as this will scratch you coins. With patience you should be fine and good luck. Below is a link to the acetone I used. https://www.amazon.com/MG-Chemicals-Acetone-Pure-Grade/dp/B00M47X53Q
Pure sodium bicarbonate crystals have a Moh's hardness of 2.5. Copper,silver and gold have hardness of 2.5-3, so it is stretching the safety by using it as a cleaning agent. Luckily tooth enamel is around 5.
If you are not concerned about the value of these coins, instead of baking soda, just take a little toothpaste (any kind will do, but probably "white" and not "gel"). Rub it on both sides of the coin. Rub it with your fingers/ paper towel/ rinse and you will be shocked how "clean" it gets.
Yes you're right but in Aluminium coins only. It does wonders in golds and silvers. Removes tarnish and original luster remains. You may use it in cheap coins and you'll agree. If you overdone it with coopers they turn in blue. Never use it in red or red brown coopers.
The baking soda/aluminum foil thing reverses the toning process, not the PVC plasticizer process. It has no effect whatsoever on PVC. All you managed to remove was whatever was loose enough to come away in warm water, and the mild abrasive action of the dissolved baking soda. The PVC is still there, eating away the silver.
