Hard-To-Buff Silver Deposit

Q. I work for a specialty silver plating company that restores silver-plated candelabras, silverware and other household items. Our silver plating bath has been well-maintained in terms of testing and maintaining proper chemical composition, but we have noticed over the last few months that the plated deposits are more difficult to polish and buff. Do you have any suggestions for resolving this problem? S.L.

A. Start by checking the current density in the bath. Low current density will enable you to deposit silver, but if it is at the very low end of the suggested range you can get harder-than-normal silver deposits.

There are several types of impurities that will cause silver deposits to become hard and difficult to polish and buff, including the presence of iron and high chlorides. Lead, tin, nickel and organics also can cause this problem.

To remove the unwanted organics, filter the plating solution through activated carbon. Keep in mind, however, that activated carbon treatment will also remove desirable organic additives, so you will most likely have to reconstitute the bath with the required additives. To remove most of the “tramp” metals mentioned above, dummy the bath at 2 asf for 12 to 24 hrs.