Continue from: “My apprenticeship…”
Hi John and Alan,
So, how does hitting silver with a nylon mallet compare to
striking/reducing/raising with a metal hammer, when it comes the
need to anneal? Thanks!
Jim Binnion is Mr. Science - I mean that sincerely, and he can answer in his inimitable way. On a practical level, you are dealing with the deformation of metal. More deformation=more hardness. It doesn't matter, really, whether it's bending, twisting, or smashing. An exaggeration: if you sit there and pound on a piece of silver with your finger nails all day long, it will not harden, because you're not deforming the metal, even though you are pounding on it. A nylon mallet will harden some - depending how hard you hit with it - it's not the hammer so much as the bending of your bracelets that's doing it, though.
Mr Science here 
John you hit the nail on the head of course. Cold
work is manipulating the metal by bending, hammering, twisting,
rolling, drawing etc. When trying to define how much cold work has
been done forging, rolling or drawing are easy to determine you just
measure the starting thickness vs the thickness after working and
you can determine how much stress you put into it. However bending
and twisting are much harder to figure out as they don’t reduce the
section of the work much relative to the amount of work you put into
the metal. Alan, in the process of bending your bracelet you are
compressing the inner surface of the metal and stretching the outer
surface. This does indeed produce significant cold work and the
resulting work hardening and they can possibly require annealing
before you can complete the work. Unfortunately there is no simple
way to determine when you have put enough work into an object by
bending to get an optimum crystal restructuring during the anneal.
So you must rely on your hard won experience of just how far you can
push the metal before it breaks then anneal just before you reach
that point. From my experience a bracelet in most silver and gold
alloys should not need several anneals to bend it round the mandrel.
What you may be experiencing is the stiffening of the metal as it
begins to work harden makes it harder to bend and you may need a
bigger hammer or a different system of leverage to bend the
material.
If you anneal too hot or too often (or both) you will end up with
metal that has an orange peal surface and is not as strong and
ductile as properly annealed metal. This will show up in working and
also in polishing as orange pealed over annealed surfaces don’t take
as good a polish as properly handled ones (correctly annealed and
left in a hard state before polishing).
Hope this helps,
Jim
James Binnion
@James_Binnion
James Binnion Metal Arts
360-756-6550