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Smut from silver plating bath

We are operating a conventional matte silver bath 4.8 oz/gal silver cyanide, 8 oz gal potassium cyanide. The bath has stopped plating. presently all we get is a brownish/black smut on the cathode area. We have filtered and carbon treated with no success. We tried to add hydrogen peroxide (in a beaker)to see if we had an organic that the carbon was not removing. The plating bath too nearly 1/2 hr and then started to react and turned a greenish tint and formed a large amount of sludge. we are seeing a slight blackening of the anodes. The bath is ten years old and likely needs to be replaced. we would like to know what caused this sudden change. we shut down for a week at christmas and were not able to plate when we started up. The bath did fall to 50 deg F. We replaced our anodes in October with 999.9 pure.

William Morgan
Electronics Mfg - Saratoga Springs, New York, USA
2006

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You may need to check your free cyanide ,if it is low , and the carbonate,if it is not too high.
good luck

Khair Shishani
aircraft maintenance - Al Ain, UAE
2006