I think that I would be justified in saying that I handled more
rose (red) gold than anybody on this forum, except members who were
trained and worked in Russia, because it was the only alloy that
was used. Fitted parts do not fit anymore if annealing or soldering
done incorrectly, and just because you can swing a hammer at it,
does not change that. It is important fact to be aware of if one's
practice done on fractions of millimeter scale. Not everything is
judged by "Can I hit it with a hammer".
I work from the raw laminates to finished items as you say at sub
millimeter precision. 100 lb Power hammer to gravers and files. I
work with red gold daily so possibly you have worked more of it but
my experience has not shown this fragility you refer to.
I work from the raw laminates to finished items as you say at sub
millimeter precision. 100 lb Power hammer to gravers and files. I
work with red gold daily so possibly you have worked more of it
but my experience has not shown this fragility you refer to.
In this frame of reference, the fragility refers to material
requiring extra care as compared to another. I do not recommend
plunging anything red-hot into the liquid, but 2 phase gold-copper
alloy especially so. Another thing is that application of the alloy
makes a lot of difference whether of not certain properties are
revealed.
As an example here is the couple of pictures of a ring from my
riviere series.
It is still unfinished, and it is not red gold, but sufficient for
demonstration.
The inner band is constructed separately from the gallery. Gallery is
shaped to the stage shown, and then soldered to the inner band. The
starting shape for the gallery is simply a hollow ring with 3-sided
box profile, both sides of which is fitted perfectly to the inner
band. Then sides are soldered to upper ring, and the assembly is
shaped. There are 3 soldering operations before the shaping. if
alloy is plunged into water from red-hot state, the parts will not
fit anymore, and that will create gaps between soldering points,
which would have to be filled with solder. But that would be ugly.
There is not much cleaning that can be done with this type of a
design. If joint cannot be made attractive by lightly buffing, it
goes to the scrap pile.
Since we are on the subject, this is also an example of use of
jewellery saw. This cannot be done with a file because of force
involved in filling is sufficient to affect the shape. If filling
lightly, it would take far to long to be viable. The whole thing is
done with 6/0 blade. Files are only used for finishing.
Dimensional stability is not the only issue. Marks will be left on
highly polished parts if handled red-hot. Depending on how alloy was
cast, micro-cracks are possible. They are not visible without
magnification, but when worn, could become source of skin irritation
due to accumulation of organic matter, and it is next to impossible
to clean it. If anybody ever had jewellery which is simply
uncomfortable, it could be the reason and not some mysterious
allergy which nobody knows how to treat.
I had a question arise in the casting class I teach as to whether
there is a time when it is too late to quench the casting. We cast
in sterling, and quench in water when the button has just lost its
redness and is a dull grey. Is this the best time to quench for
sterling? Is there a time when it is too late to quench, i.e., the
metal is too cool to be properly annealed?
In my experience teaching casting, the answer is “no”… the main
reason behind the hot quench of silver castings is to blast off the
investment so the work can be cleaned without a major excavation
project to dig it out of the plaster. Yes, the best time to do it is
after the button has lost all its redness, as the metal will have
cooled enough to avoid cracking due to thermal shock. If you’re doing
stone-in-place castings, you really need to leave them un-quenched
until the flask is cool enough to handle with bare hands, then dig
them out of the plaster (water jets can help with this).
Hope this helps! And if any of you metallurgists out there (James
Binnion? Peter Rowe?) know of any other metal structural reason why
quenching of silver should be done at a specific point after casting,
I would love to know that, too!
Karen Goeller
No Limitations Designs
Hand-made, one-of-a-kind jewelry www.nolimitations.com
Hope this helps! And if any of you metallurgists out there (James
Binnion? Peter Rowe?) know of any other metal structural reason
why quenching of silver should be done at a specific point after
casting, I would love to know that, too!
With sterling one possible no no is quenching too hot. Sometimes if
you quench too soon you can get hot tearing of thinner parts of the
work. It is best to allow the button to loose any red color before
quenching. There is not much that quenching will do to change the
crystal structure of the cast work. The crystal structure is already
set before you can remove the flask from the casting machine (within
a second or two of the metal entering the flask). Beyond that the
main objection to any hot quenching is that it liberates ultra fine
silica particles. No matter how fast you stick the flask in the water
you will get some amount these minute silica particles in the air and
they are a serious health problem (silicosis) with chronic exposure.
Cold flasks are harder to break out but don’t pose the health risk.
Proper ventilation of the investing and casting area will greatly
mitigate this issue but it is something too many of us ignore.