Red gold alloys. [was: correction to sterling annealing]

Jewelry Discussion
1

There are so many different alloys and as you know, each has its
own physical and mechanical properties which are not always
logically predictable. I have worked in two of the reddest 18k
alloys: Au 750 + Cu 200 + Ag 50, as well as Au 750 + Cu 250. In
neither case did I find the metal to be overly brittle or
unworkable. This may be due, in part, to the fact that these
alloys are quenched in alcohol rather than water.

Alan

2 
   This may be due, in part, to the fact that these alloys are
quenched in alcohol rather than water.

I haven’t had experience with red alloys, should they always be
quenched in alcohol? Is there a book/source that gives information
on in which fluids to quench which metals ?

As one who has a lot to learn about this craft/art, I would like
to thank all those who are so generous with their knowledge.

Happy New Year to all,
Lorri Ferguson

3 
  There are so many different alloys and as you know, each has
its own physical and mechanical properties which are not always
logically predictable. I have worked in two of the reddest 18k
alloys: Au 750 + Cu 200 + Ag 50, as well as Au 750 + Cu 250.
In neither case did I find the metal to be overly brittle or
unworkable. This may be due, in part, to the fact that these
alloys are quenched in alcohol rather than water.

The addition of even small amounts of silver to copper/gold 18K
alloys seems to prevent the formation of that ordered array
structure I referred to. It seems to be a danger only in
straight copper/gold alloys, at or near the 18K ratio, at which
there is a 1:1 ratio of gold to copper atoms. Quenching in
anything after annealing will prevent the formation of that
brittle structure, since it doesn’t form at annealing
temperatures, and if cooled quickly through that temperature
range in which it does form, no problems will be encountered.
It’s only when the metal is slowly cooled, or not heated high
enough, that this occurs. And even then, it’s only a problem if
some working process starts cracking before the next operation in
which the metal is again heated to annealing temp (which disrupts
that structured array again).

Peter Rowe

4

I do not know a book with about which fluids to use
for quenching different alloys. This is the kind of information
that, to my knowledge, has not been recorded, but has been passed
down verbally. Alan

5

Hi Lori, where I was an apprentice, we had a watch and
clock-maker’s workshop attached to the jeweller’s workshop and
they always quenched brass and copper parts in methylated spirits
for the main reason that it cleaned the oxidised surface so well.
Perhaps there was a more deep and meaningful metallurgical
reaction taking place as well. I’ll watch the answers to your
post with interest. Best wishes for the New Year, Rex from Oz.

6

Hello Lorrie, If you decide to quench metal in alcohol [it is
great for white gold], be very careful. It is a dangerous
process. Use a small container for the alcohol. Work in an area
away from all flammable materials. Make sure you drop the metal
quickly and without hesitation into the liquid. It must
completely submerge. Is there are any glowing bits on your
tweezers, this will surely ignite the fumes from your alcohol.
Keep a cover for the container close by, ready to smother the
flames that shouldn’t but do ossasionally occur. Have fun. Tom Arnold

7 
What're the benefits of quenching in denatured alcohol? (aka
methelated spirits, meths)    Do you dilute it?

I know that meths is slower than water, ie the metal cools down
slower. And from memory stg comes out cleaner, so I guess there
is less oxygen in it.

The reason why silver, copper, brass, gilding metal etc., all
come out ‘cleaner’ after heating and then dipping in alcohol
(methylated spirits) is because the alcohol molecule reacts with
the oxides on the metals and actually combines with the oxygen in
the oxide, leaving the free metal. However, if the metals
happen to be close to or above red heat, the alcohol will catch
fire. Methanol (methyl alcohol), iso propanol, and other alcohols
will also work similarly, and so will many other solvents. Cheers,

     /\
    / /
   / /
  / /__| \      @John_Burgess2
 (_____)

At sunny Nelson NZ

8

WOW!! Do I understand this quench method for red gold???..
after casting… you place the item in alcohol?? or are we talking
about just one item reheated and then quenched in alcohol???

Thanks

Jim