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A GLOSSARY of MILLED BANDS
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 SMP Silver Salon Forums
 American Silver before sterling
 Fire scale on American silver
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| Author | Topic: Fire scale on American silver |
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labarbedor Posts: 353 |
posted 01-25-2004 04:32 PM
  
I have been trying to find a reference to the occurrence of fire scale in early American silver. Fire scale is the result of annealing process that doesn't show on a recently fashioned piece of silver, because the surface has been pickled and burnished. When this purer surface silver wears off, the fire scale surfaces. I remember reading somewhere that this was more common on early American silver than on English silver. I guess this could be the result of the generally lower silver content of American silver, but then why isn't it more common in lower grade European silver? I don't remember seeing it on any English silver, except for one piece that was badly worn, and the fire scale was far darker than the grey mottled look on American pieces. I believe the reference said that something differentiated the way American silver was made perhaps something like more lead impurity, or something like that. I include a photo of one example of what I am talking about. Of course I would love to find the reference again, but a good explanation would do fine. Thanks. IP: Logged |
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FredZ Posts: 1070 |
posted 01-25-2004 07:39 PM
Firescale has been the scurge of all silversmiths due to the copper content in the alloy used. Aram Berberian's father wrote a superb article explaining fire scale and why it was formed. It is possible to remove it before the final stages of polishing and finishing. This usually involves metal removal by abrasion or chemical removal. I have seen scale in many fine items from all ages. I have Arts & Crafts Movement items that were left with the grey color of the scale and have a warm appearance to them. I have seen images of Revere items with scale on them exposed from the years of polishing. I doubt if there is a special process used on English silver that allows it to be less plagued with scale. Perhaps it is the fact that the scale was removed before it was completed and offered for sale. Scale is only formed during the annealing process of fabrication. Annealing can occur several times during the manufacture of a silver alloy article. Each time it is heated to high temperatures during soldering and annealing the potential to oxidize the copper molecules near the surface is increased and the layer of scale can grow deeper. The application of flux and the use of the lowest temperatures needed to do the job are the best deterrents to creating firescale during fabrication. I no longer find firescale to be such a horrible thing, particularly on antique silver. I do try to avoid it in my work. Fred IP: Logged |
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