Friday, February 24, 2012

Fine Silver is Beautiful, But Sometimes Sterling is Better


by Janet Alexander
Technical Advisor

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
  • Torch
  • Kiln brick or fire-proof surface

The Steps:

  1. Heat sterling silver until it turns black (above left).
  2. Quench in water.
  3. Pickle metal until it is no longer black. Warmed pickle works faster.
  4. Rinse metal with water.
  5. Repeat until the metal no longer oxidizes (above right).

Remember:

  • 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.
In a future post, I plan to address embedding sterling silver into sterling silver metal clay. Next time, I will give some tips I use everyday in working with metal, including work-hardening wire.

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.

6 comments:

Lora Hart said...

Great tip Janet! I use Alum from the spice aisle of the grocery store as a pickle. I live in a tiny apartment with two cats and didn't want the chemicals in my house. Alum is used to turn a cucumber into a pickle! Any acidic liquid will (eventually) get rid of oxydation. I've even heard of spmeone using lemomaide Kool-Aid!! Imagine!

Janet Alexander said...

Cool! I knew that the term "Pickle" came from the old days of using solutions for pickling veggies. I had never heard of using Alum! I'm not much of a cook, so I have no idea as to what is used for making pickles. Great tip!

Julie Cannariato said...

Thanks so much for this info Janet. I have been wanting to learn depletion gilding but have been intimidated by some of the methods I have seen. This looks much less complicated and I LOVE, LOVE, LOVE the way you explain things. You certainly have great technical writing skills.
Keep up the great job!
Julie Cannariato
ArtZcat Creations
www.artZcat.com

Fai said...

Thank you so much for posting this. I've been looking for an instruction like this forever.

lee woo said...
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Leslie Lim said...


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