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Experiment with fusing / granulation


Since I wasn’t having much success getting pure silver to fuse, I
searched the 'Net for on a similar process, granulation,
and learned that:

  • Pure silver is difficult to fuse because its fusing temperature is
    perilously close to melting temperature (which I can verify).

  • Fusing is facilitated if there is copper at the join. Some jewelers
    plate a layer of copper onto the metal grains before attempting to
    fuse them to the supporting piece. Others apply copper in solution.

  • Metal should be fired in a reducing atmosphere. An “organic glue”
    (gum tragacanth, hide glue, etc.) is used to hold the metal grains
    in position. The glue burns away during firing, using up oxygen and
    providing the reducing atmosphere.

My experiment:

  • Intead of plating a layer of copper onto the silver, I applied a
    commercial liquid that contains ammonium chloride and copper sulfate
    (it’s sold as a “patinating” treatment for bronze).

  • I used sugar as a glue, because it was handy. It is also organic
    and, being dry, didn’t make the patinating liquid any runnier.

  • For the reducing atmospheRe: I figured the sugar would burn and
    use up some oxygen. I also used a charcoal block for firing.
    Finally–don’t laugh–I fired some of the pieces on a piece of
    bread. (The bread didn’t contribute much except a slight mess. Okay,
    go ahead and laugh.)

Some of the silver fused, but I don’t know whether it was due to the
copper/sugar or just having more practice with the torch. There were
some odd results: Wherever I applied the copper/sugar solution, the
metal was shiny and stiff. The rest of the ring was matte white and
dead soft.

Did the copper solution convert the fine silver into sterling?