Working with Bi-Metals

Name: 22K/Sterling Silver BiMetal

Composition:
Volume: 8.3% 22K gold, 91.7% sterling silver
Weight:12.5% 22K gold, 87.5% sterling silver.
Description:One layer 22K gold, one layer sterling silver. The 22K layer is 1/8^th of the volume, 1/12^th of the thickness.
Hall Mark:1/8 22KGF
Melting Point: Has not been determined, but will not melt below 1432° F.
Annealing range:1150°-1350° F.
Density: About the same as sterling silver.
Approximate weight/square inch: 24ga-3.64 grams,18 ga-7.28 grams.

Name: Shakudo-Sterling Silver BiMetal

Composition: 10% Shakudo(4% gold, 96% copper), 90% Sterling silver
Description: One layer shakudo, one layer sterling silver. The shakudo layer is 1/8^th of the total sheet volume.
Melting Point: The approximate start to melt point is1432°F.
Annealing: Temperature from 1150°­1325°F. Anneal like sterling silver with flux as a temperature indicator. Do not heat above 1325°F.

Note: This material starts to melt at a significantly lower temperature than sterling.

Density: About the same as sterling silver.
Approximate weight/square inch: 24ga-3.3 grams.

Name: 15% Shibuichi-Sterling Silver BiMetal

Composition: 10% Shibuichi(15% silver, 85% copper), 90% Sterling silver
Description: One layer shibuichi, one layer sterling silver. The shibuichi layer is 1/8^th of the total sheet volume. 
Melting Point: The approximate start to melt point is1410°F.
Annealing: Temperature from 1150°­1325°F. Anneal like sterling silver with flux as a temperature indicator. Do not heat above 1325°F. Note: This material starts to melt at a significantly lower temperature than sterling.
Density: About the same as sterling silver.
Approximate weight/square inch: 24ga-3.3 grams. 

Note: Patinas may be waxed or sealed to help prolong their life. They will inevitably change with time and usage. The chemical balance of the wearer may also affect the color. 

Characteristics: BiMetals work very much like sterling silver. Do not be afraid to push the material. Excessive annealing should be avoided. This material can be pattern developed by selectively removing the top layer to expose the sterling. Relief patterns can be developed by etching.

Soldering: Use the same considerations as if soldering sterling silver. Use the lower melting temperature easy and medium solders with a flux coating to help avoid firescale. 

Finishing: Finishes may be developed with the same polishing products as used on sterling and karat golds. Check closely for dark shadows on shakudo indicating firescale.

Etching: Three etchants may be used: 1) MultiEtch, 2)30% solution of Nitric Acid and water, 3) mild Ferric Chloride. Rinse with baking soda and polish lightly. 

Patinas:

Antique Patina or traditional liver of sulfur can be used to patina sterling silver from brown to black.

Use Baldwin's Patina on copper/sterling and copper/brass Mokume-gane to color the copper brown. Use Baldwin's or Antique Patina to turn Shakudo purple/black. Firescale will show as orange splotches against the black and should be removed.

Shibuichi can be patinated to a wide range of grays, olive greens and even sky blue. Pale greens can be produced by alternately swabbing with clear ammonia and rinsing in warm water. Heavy textured greens can be produced by adding salt to an ammonia/vinegar solution. Baldwin's Patina will produce grays and pale olive greens.