Silver Deposit/Overlay
Silver Overlay is the name used when this electroplating process is done on glass or porcelain. it can also be done on enamel and in the NBS button world it is frequently called Silver Deposit (page 80), so as not to confuse it with overlay on glass, which is different. Some might call it Silver Resist, but that is a misnomer as discussed in the book. Anyway, these are hard to find and understand so I am giving a bit more information than what is in the book.
In the process to form a Silver Deposit, a mixture has to be fired onto the enamel first. This mixture has to be attached to the metal of the rim of the button as this rim is what is attached to the electroplating node. This attachment allows for the current of the process to extend to all parts to be electroplated. Just as in a Silver Deposit on porcelain needs a metal tab on the back of the button that attaches to the metal shank, so too you need a complete metal connection when done on enamel.
In terms of determining if something is a Silver Deposit or a Champlevé, one more characteristic than what the book describres is important to check... as the Silver Deposit is over the enamel, there has to be a slight lip to the metal where it attaches to the enamel. In the first button below, the silver frame is a) attached to the rim of the button and b) can be felt (ie: has a lip) to be above the enamel. The 2nd button which is a Basse Taille Champlevé enamel has a) the metal on the top attached to the rim, but b) is flush with the enamel (part of the process of Champlevé is when done enameling, the top is ground down to be flush with the metal). |