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Confusion about annealing gold


#1

I read so many conflicting things about how to keep yellow gold
bezel soft. I have been told it is the opposite of silver: anneal it
and then let it completely air cool. However, I have also read both
to anneal and then quench immediately. Why the confusion? Which is
right?

J. S. Ellington
jsellington@cs.com


#2
        I read so many conflicting things about how to keep yellow
gold bezel soft. 

Sue, Anticlastic raising requires one to anneal frequently…for the
metal, (usually 18k,) workhardens quickly. Thus, I’ve tried all
concepts of annealing, and here are two suggestions.

1;mark metal with a Sharpie pen and heat until mark burns away, you
are at proper temp, BUT hold that temp for about a minute, then
quench.

2; coat with alcohol -borax solution, heat until coating ‘glazes’,
hold for a minute, and quench. Then you’ll have to dip in heated
pickle to remove ‘glaze’.

These have worked for me with all metals except white gold. which I
do the same procedures, except not quenching immediately, and then
only in alcohol. Theory is crystals relax at heated temp, and must be
quenched to stay in same formation. Thomas Blair


#3

An acquaintance who has worked in gold for years and does expensive
and beautiful work tells me that in order to get the gold soft, you
have to let it air cool after annealing ( just the opposite of
silver). Is that consistently true for all karats?

J. S. (Sue) Ellington


#4
An acquaintance who has worked in gold for years and does
expensive and beautiful work tells me that in order to get the gold
soft, you have to let it air cool after annealing ( just the
opposite of silver). Is that consistently true for all karats? 

So far as I know, and in my experience, it’s actually SELDOM true.
Yellow and rose/red Gold alloys containing copper can be
age/precipitation hardened, and a slow cooling will at least start
this process. Some alloys, the red golds, especially 18K red gold
(just copper and gold) MUST be quenched of they become not just
harder, but very brittle and hard. Nickel white golds too,
sometimes age harden quickly enough that a quench vs a slow cool is
the difference between being able to work it fairly easily, and
hardly being able to work it all…

However, slow air cooling does have one advantage sometimes. It
doesn’t introduce unequal stresses to the metal as it cools in the
same way a quench can do. so some pieces that might warp when
quenched, need to be slow cooled.

Peter


#5
    An acquaintance who has worked in gold for years and does
expensive and beautiful work tells me that in order to get the gold
soft, you have to let it air cool after annealing ( just the
opposite of silver). Is that consistently true for all karats? 

No It is not true for any of them. Some nickel white golds need to
be air cooled to prevent imparting a high residual stress in them
from the rapid cooling but otherwise gold alloys should be quenched.
In fact many gold alloys will be harder if you let them air cool and
some can actually fracture very easily in this air cooled state
because they have become so brittle.

Mark Grimwade who is a metallurgist and teacher in his book
Introduction to Precious Metals (ISBN 0-408-01451-2) has a list for
the annealing temps for the following alloy’s

Fine Gold 200C  (392F) (black heat)
Fine Silver 200C  (392F) (black heat)
22-18K Colored Golds 550-600C (1022-1112F)  (very dark red)
14-9K Colored Golds  650C (1202F) (dark red)
Pd White Golds 650-700C (1202-1292F) (cherry red)
Ni White Golds 700-750C (1292-1382F) (cherry red)
Sterling Silver 600-650C (1112-1202F) (dark red)
Platinum 800C (1472F) (bright red)

His torch annealing instructions are as follows:

"It is important to do torch-annealing in a darkened corner of the
workshop if consistency is to be obtained, for ones judgement of
colour temperature is seriously impaired by reflections of light
from windows, fluorescent lighting, etc. The reducing part of the
flame should be used to keep surface oxidation of base metal content
in karat golds and sterling silver to a minimum, Items should be
allowed to cool to a black heat , i.e. when no reddish colour due to
heat is observed, quenched into cold water and then pickled in a hot
sulfuric acid. The object of this is twofold. First, any oxide scale
will be removed by pickling. Secondly, further changes in the
microstructure due to to ageing and ordering processes (see Chapters
6 and 7) can occur during slow cooling which will harden the alloys,
and this will be undesirable if further working is to be done. Rapid
quenching prevents ageing and ordering reactions and retains the
maximum softness and ductility imparted by annealing. "

This book is out of print but can occasionally be found in online
used book stores is well worth owning. Mark has spent many years
teaching metallurgy to artists and goldsmiths and provides a good,
understandable text on the metallurgy of precious metals

Jim


#6

I have a small paper of small scale production of sheet and wire. It
goes into pouring of ingots,production do shaped wire and flat
stoc,drawing of wire, annealing, and charts. I will be happy to send
to you… advise of address

Andy “The Tool Guy” Kroungold
Sales/ Tools and Technical
Stuller Inc.
337-262-7700 ext. 4194
337-262-7791 fax
andy_kroungold@stuller.com