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What concentration of H2S is needed to tarnish silver?
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What is the minimum concentration of H2S needed to cause tarnishing of silver? Assume the environment is air conditioned, 20 degrees C, illuminated by electric lights (fluorescent lighting - Is UV generated by this type of lighting?) David Jarvisan assayer - Sheffield, U.K. +++ There is no precise answer to your question as the amount of tarnishing you see will be a function of the Relative Humidity, gas concentration and time of exposure. Silver will react with extremely low levels of hydrogen sulphide. However, the gas is so pungent that it is difficult to withstand more than 5-10 ppm of the gas - if this gets exceeded you can become desensitised and not smell it at all; this is when it kills you! You will be aware that silver will go black in an atmosphere where you cannot smell hydrogen sulphide, so the minimum level will be in the ppb or even ppt range; however, the detection of the reaction will be dependent on how long the silver is exposed to the gas. The rate of reaction will also be dependent on the relative humidity of the air, as the water is needed to dissolve the gas. Hydrogen sulphide and silver react to form black silver sulphide, one of the most insoluble salts of silver and this is what causes the tarnish. However, it can be very easily reduced by putting it in a dilute solution of sodium carbonate and attaching a piece of aluminium foil to the article. Fluorescent lights do produce some UV light, depending on the filler gas, but commercially available domestic or general purpose industrial lights do not constitute a UV health hazard.
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Has any research been published that defines the optimum moisture, hydrogen sulphide, temperature and UV to cause rapid tarnishing of silver. Is this a project that is of interest?
David Jarvis- Sheffield, UK
Hi, David. Unfortunately, I can't figure out where you're going. Are you trying to tarnish silver (which is certainly easy enough to do with
Liver of Sulphur
[linked by editor to product info at Dick Blick]), or are you trying to explain why silver tarnished in some situation, or are you trying to develop a tarnish resisting treatment for silver? Please try to start with: "Here is my situation . . ." and maybe we can help.
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |
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I'm doing a science project where I wish to demonstrate electrolytic cells involving silver. So... what concentration of Hydrogen Sulphide would I need to expose say an inch by inch square of silver to in order to see a visible tarnish within a day or two?
Justine P.- Yeppoon, QLD, Australia
July 21, 2008
I am an artist trying to tarnish silver leaf adhered to paper with a synthetic polymer product called Rolco aqua-size. When I use Pax Silver Blackener, which contains sulfuric acid, the aqua-size dissolves and the leaf peals off. A spokeswoman for Rolco did not disclose the chemistry of the product, but she did tell me that once cured aqua-size dissolves in acetone [linked by editor to product info at Rockler]. She had no information on sulfuric acid's affect. Is there a way to tarnish silver leaf in a fairly controlled way using readily available chemicals/household products that will not dissolve synthetic polymer? Thanks.
James Wechsler- New York, NY USA
July 21, 2008
Hi, James. Liver of sulfur is very available and far less corrosive that sulphuric acid, but I can't guarantee that it won't affect the paper or polymer; you'd need to try it. Boiled egg yolks, sealed in some way to keep their gasses on the silver might work too.
Regards,
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |
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July 25, 2008
Thank you. Would a powdered form of Liver of Sulfur tarnish silver? Or does it need to be liquid? What about other dry chemicals containing sulfur, such as gypsum or pure sulfur? JW James Wechsler- New York, New York USA July 25, 2008 Hello again James. Liver of sulphur is available as a dilute liquid or as a solid to be mixed with water to make a liquid -- Whether solid liver of sulphur powder would work in dry condition, sorry, I don't know. Gas from the eggs yolks should work without any solid or liquid involved though. Regards,
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August 4, 2008 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
Is there an effective method of tarnishing silver without the various solutions coming into contact with it.
Specifically, I am a drawing with silverpoint (ancient method of drawing using pure silver wire much like you would a pencil) and I would like to be able to accelerate the tarnishing process, but because it is applied so thinly on a paper surface, I can't brush or spray any solutions on it.
I also have the exact same question regarding copper.
Metal artist - San Antonio, Texas
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August 5, 2008
Hi, James. Sulfur dioxide or hydrogen sulfide gas will do it, but they are very hazardous. I think egg yolks will give off a small amount but can accomplish the task. Regards,
October 27, 2008 I have a picture frame covered with silver leaf. There is no varnish on the frame. I want to tarnish the silver. No solution can be applied, or the silver will come off. I understand the fumes of hydrogen sulfide or sulfur dioxide will accomplish this task. Does anyone had advice or experience on how to accomplish this. Would an open container with either chemical in a sealed box with the frame produce a tarnished finish? Thank you for any advice. Peter Zokosky- Long Beach, California, USA
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