by Janet Alexander
Photo by Marsha Thomas
I love the look of fine silver with its bright white color, but it is so malleable. It doesn’t hold its shape very well! So, instead of using fine silver wire for earring wires, I use sterling silver.
In a previous post I recommended not using fine silver for earring wires. It’s too soft and won’t hold its shape no matter how much it is work-hardened. Work-hardening sterling silver, with its copper content, makes it stiffer and it holds its shape better.
However, the copper content in the sterling silver wire keeps it from adhering to the fine silver metal clay when embedding it. This is because the copper in the sterling silver oxidizes when heated with a torch or on a kiln shelf.
Removing the copper from the outside layer of the sterling silver allows it to adhere to the fine silver. This is called depletion gilding. The process essentially brings the copper to the surface of the metal by heating the sterling silver with a torch. The metal is then cleaned in pickling solution. The pickling solution absorbs the copper from the surface of the metal. This is why the pickling solution turns blue over time. This process is completed over and over until the sterling silver no longer turns black when heated.
The depletion process requires the following materials:
- A bowl of water
- Jeweler’s pickling solution (Sparex, Citric Acid, or PH Down for pools)
- Copper tongs
- Kiln brick or fire-proof surface
- Heat sterling silver until it turns black (above left).
- Quench in water.
- Pickle metal until it is no longer black. Warmed pickle works faster.
- Rinse metal with water.
- Repeat until the metal no longer oxidizes (above right).
- Take care not to sand the metal after depletion gilding. This removes the layer of fine silver.
- After embedding the sterling silver into the fine silver metal clay do not heat over 1300˚F. The metal becomes brittle.
- Work-harden* the metal after firing it in metal clay by hammering the sterling silver with a rawhide or plastic mallet against an anvil.
I appreciate all of you who posted questions and comments last time. Keep it up. The best way to learn something new is by asking questions and sharing!
*Work-hardening involves compressing the metal so that it becomes rigid.