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Silver solution/precipitation thickness build up

July 10, 2009

According to my reading of literature, only silver that is in contact with the sensitizer will actually stick to the substrate of interest. However, when adding multiple spray passes the opacity of the silver application clearly increases. Is the silver simply filling in spaces with each pass or is there actually a growth in thickness of non-water-rinsable silver being developed. My concern is with excessive build up of silver in very fine part features (multi-faceted lens). The parts are to be electroplated and I don't want to a: apply too little silver and not have continuous continuity or b: apply too much and lose detail.

Thanks in advance

Kevin Taylor
Hobbyist - Columbus, Ohio, USA

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Hi, Kevin. The thickness should not be a problem: two-part silvering was (and possibly still is) used on the lacquer masters of vinyl records to start the duplication process. The reducing solution reduces the dissolved silver ion to silver metal, so yes the thickness will build. In precision applications the silver is sprayed on while the part is on a spin table (similar to what kids use for "spin art". This helps coverage and uniformity of thickness.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 10, 2009