Metal finishing Q&As since 1989

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Thiourea use in jewelry cleaning

I recently purchased a Silver Jewelry Cleaner. I, unfortunately, used this product without carefully reading the instructions since I have purchased other products by this company before without adverse effects.

I included many silver pieces with semi-precious stones in which the stones dissolved on the surface. After carefully reading the label, I further noted that the product was considered a "cancer causing agent" in the State of California. Being concerned with this warning, I contacted the company and inquired about the agent/chemical which is called Thiourea [on eBay or Amazon].

The company stated that thiourea was a low level cancerous agent noted with the State of California and that I, and my jewelry, were safe from this agent with simple rinsing.

My questions are as follows: Would you consider this agent a safe agent to continuously use? Is simple rinsing enough to remove the agent? I was told that buffing the top layer of the damaged stones would be perfectly safe without agent residue. . .is this true? Are the levels of this agent minimal and why such a rating from the State of California? Your time and attention is greatly appreciated.

Thanks kindly,

Denise Knapp
hobbyist - Henderson, Nevada
2004

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2004

The State of California has advised you that this material is unsafe, Denise. No one will pooh-pooh that specific warning for fear of being challenged, insulted, threatened, and possibly sued by anyone who has ever used Thiourea [on eBay or Amazon] and who finds themselves sick in any way and for any reason. Sorry.

Yes, lots of us feel that over-zealous warnings by California on everything from zinc plated hardware to gas stoves are precisely 'the little boy who cried wolf' fairytale that we were all warned about brought to real life, and working to the detriment of actual safety -- but there is little likelihood that anyone can downplay a very specific warning from a state regulatory agency as you would like them to, especially about thiourea. Sorry.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey