Metal Clay Tarnishing
Hi, hoping that somebody might me able to help me!
I have a customer who recently purchased 2 charms (made from Art Clay) from me to attach to her own silver charm bracelet. She took my charms, along with several others to a very well established jewellers to have them soldered onto the bracelet and was very upset to find that the charms that I have made had turned black and patchy.
Several of the other charms have also been damaged (missing diamonds and also with a slightly pitted and dented surface) so she is going back to speak to the jewellers, but it is a mystery (not to say a concern) that my metal clay charms have tarnished in this way. She is able to polish them up, but they blacken again almost immediately
Any suggestions would be really gratefully received!
Silver - especially the nearly pure silver of Art Clay and PMC - is prone to blackening from exposure to sulphur compounds, especially hydrogen sulphide. This comes from a wide variety of common sources and foodstuffs and is impossible to avoid.
It may be that your client has some environmental feature that is especially high in sulphur (working with eggs, leather, sea-weed; unscrubbed natural gas, car fumes...) and that the fine silver charms are especially prone to this.
Scintered metals (like Art Clay) are porous and might retain chemicals like liver-of-sulphur if dipped into them, perhaps by a well-meaning restorer attempting to recreate patination.
There isn't a great deal one can do about it. Dip-cleaning and spraying the charms with a fixative or wax after polishing will help temporarily but it quickly wears off.
Thanks for your help Joe, it'll be interesting to hear and learn from what the jewellers have to say.
There are tarnish resistant silver alloys - Cooksons have 'Reflections' and used to stock 'Argentium'. But these are not available as clay - clay only works with very high purity silver. It will always be prone to black tarnish.
It is also softer than sterling and prone to marking and pitting - I was a bit upset with the London assay office recently for eschewing my tissue packaging and dumping the fine silver in with the sterling, necessitating a lot of re-polishing before it went out to a customer. Grrr!