I was always taught to quench after annealing (except brass). But
then, years ago, my students did this and their pieces weren’t
annealed. So I went to some jewelers I know and asked what was the
problem. They laughed and said don’t quench dummy, it’s work
hardening the metal.
So now I teach to air cool all metals. In a recent class a student
was having great trouble annealing and said she looked it up in a
book and it said to quench. So she did it that way.
What gives? What’s the right way? And while we’re on the subject,
why is annealing so hard to understand or see for new students?
What can I do to make it clearer?
Thanks all,
Elaine Luther
Chicago area, Illinois, USA
Certified PMC Instructor @E_Luther
Elaine, I still quench hot except for the brasses. I suspect that
the students didn’t really reach an annealing temperature. Try having
them put a dab of flux on the metal and when they see it run clear,
the metal is annealed. They should use a large soft bushy flame and
be sure to heat the metal evenly. My class hasn’t had any problems
that weren’t due to underheating or almost melting . It takes a bit
for some people to recognize the color changes.
Prof. Erhard Brepohl, in the Theory & Practice of Goldsmithing
(trans. Charles Lewton-Brain, ed. Tim McCreight, 2001) devotes 13
technical pages to annealing and age hardening gold, silver and
their alloys. Brepohl recommends the use of an electric kiln for
annealing because torch annealing can lead to overheating, torch gas
contamination and other problems. I am not capable of summarizing
Brepohl’s work, but with regard to quenching an annealed piece
(Chapter 4): (quote) "Quenching immediately after annealing is
important to retain the recrystalized structure. The simplest
quenching medium is water, but it is not ideal because it typically
removes heat too quickly. Even if age hardening is avoided,
sensitive alloys can be stressed by the rapid temperature reduction
caused by water quenching. Sometimes the stress cracks formed in
this way are only visible during later working.
“Many goldsmiths persist in the bad habit of quenching in pickle,
though it is without question inadvisable. As described earlier,
this process causes particles of acid to become bound to the
surface, where they are very likely to cause problems later.” (end
quote)
I understand that it is best to avoid quenching red-hot silver into
water because it causes stress cracks (wait until it cools slightly)
but Brepohls book takes the whole issue of annealing to a more
complex scientific level. I thought I read earlier that Orchid
periodically planned to offer some summaries of Brepohl’s book. If
so, I vote for Chapter 4.
Elaine, All alloys anneal differently. You could probably get by with
air cooling white gold, but to air cool something like 18k rose is to
court disaster. The tech tips section of the Hoover and Strong
catalogue has a great chart for all their alloys. It would probably
work for other suppliers as well. Later, Mark
Mark Thomas Ruby
SunSpirit Designs
Loveland, CO
970 622-9500 studio
970 622-9510 fax