Numismatic and History Discussion Forums > Coin Photography, Conservation and Storage
Restore lustre and re-toning naturally
Viriathus:
Hello everyone,
Even though I really value toning, two of my Alexander the Great tetradrachms had developed a rather undesirable colorful look over the years. I know toning occurs naturally and that it enhances the look of the coin, by making details stand out and adding depth, but with these two coins it no longer was the case. So, I took them to someone who cleans coins, only to find out afterwards that, unfortunately, they used electrolysis to clean them… The two coins no longer have the unpleasant colorful toning, but now they look somewhat ‘dull’ because they have lost their lustre and their appealing original black toning. I should have asked what method they would use before I handed them the coins, I regret not having been more careful.
I truly hope not all is lost. I have read here that it is possible to re-tone silver coins naturally (not artificially). I would only want to use a completely natural way to re-tone them, however long that might take. I would like to know what the best method is to do that. I have read about the following methods to re-tone silver coins naturally:
- Using sulfurated potash (flower of sulfur): Either by soaking the coin in a weak solution of sulfurated potash, or by putting the coin in the middle of a thin ring of the sulfur, without any of it touching the coin.
- Using eggs: By putting the coin into a sealed bag or container with crushed boiled or raw eggs.
I have read you can also use sunlight, however this isn’t really an option for me, since I don’t have an appropriate place to safely expose the coins to sunlight. And another method is storing the coin in abafil trays exposing them to air, although this is how they developed the unpleasant colorful toning.
I would really like to know your opinions and experiences, which you consider to be the best method, and to know about the details of the procedures, concentrations of the sulfur, how to prepare the eggs, duration of the treatment, whether there is any rinsing required after the treatment, etc. I would really appreciate your comments.
Also, I was wondering if there any harmless methods for bringing back the lustre they have lost, before doing the re-toning.
Thanks everyone for their help.
Joe Sermarini:
The luster is gone forever. You cannot restore luster.
You can probably search this discussion for eggs and sulfur and find more info on toning methods - they have been discussed before.
cmcdon0923:
You mention that you want to retone them "naturally" but then you mention possibly using either sulferated potash or eggs.
IMO, neither of these is "natural". You are exposing the coin to abnormal levels of a chemical, i.e. sulfur, in order to speed up the toning/darkening of their surfaces. And there is no way to guarantee exactly what the results will be. The only completely natural way to help them retone is to just let them exposed to the atmosphere. It may takes years, but that's the price to pay for doing it naturally.
Do you happen to have any pics of what the coins looked like before you handed them over to be cleaned?
Joe Sermarini:
There is no difference between the results of waiting years or speeding up the process with sulfur in the air from eggs. It is exactly the same process. Most of the sulfur in the air is not really natural either. It is air pollution from burning coal and petroleum. And in both cases there is no way to guarantee exactly what the results will be.
cmcdon0923:
The results may be the same, but the process to bring about the results is not. Just because sulfur is a naturally occurring substance, exposing the coin to a concentrated environment containing sulfur, does not make it a natural process......in my opinion.
If we must agree to disagree, so be it.
But if you do go the egg route Viriathus, to keep it as natural as possible, make sure they're from free range chickens. ;)
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