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Red gold alloy.. how much silver?


#1

Can someone share a red gold alloy? I want a real red, not a pink. I
know I need to add some silver to the alloy for workability, just
don’t know how much. I’m going to roll and draw into wire, so it
can’t be brittle. How much copper do I need for a good red? I want
to stay above 18K. Thanks!


#2

Brent,

This chart will tell you how red alloys are mixed:

It will also tell you that it is physically impossible to go fully
red with more than 70% gold.

I can share a “reddish” formulation if you chose to go this route.

Igor


#3

hi all, please share the chart link for red gold

Regards
Binod


#4

Thanks Igor! Chart did not make it on my end though. The 70% number
is very helpful. that stays pretty close to 18K, just bit under.
Will more silver in the mix wash out the red? I have read a
gold/copper mix isbrittle without some silver, just don’t know how
much silver to add. Please share your formula if you will.

Brent


#5

The link for gold colors is here:
http://www.ganoksin.com/gnkurl/ep827w

It is generally available in Wikipedia, just search for “colored
gold” if it doesn’t come up.

Brent, try this option from a 1991 IPMI book by Kikinzoku: 75% Gold,
7% Silver, 18% Copper.

You can increase the “red” component by progressively reducing
Silver and increasing Copper, but as you do so you will be making
this alloy more brittle and tricky to work with.

If you are in Brittain, your customers may be familiar with a 16K
alloy (66.70% Gold). Reducing gold content will allow greater Copper
concentration while keeping Silver stable. This will add “red” to
the mix. But it will be at expense of limited hallmark familiarity.

Best,
Igor


#6
Can someone share a red gold alloy? I want a real red, not a pink.
I know I need to add some silver to the alloy for workability, just
don't know how much. I'm going to roll and draw into wire, so it
can't be brittle. How much copper do I need for a good red? I want
to stay above 18K. Thanks! 

For the best red, use just copper and gold. The workability problems
arise when you don’t properly anneal it. The red golds, especially
near to 18K, if cooled slowly, will form what’s called an ordered
array structure that’s as brittle as glass if enough of it forms. To
avoid that, the trick is to quench the metal after annealing or other
heating, from barely at or just below the last trace of red glow. But
to avoid shocking the metal and cracking it by quenching in water,
quench in alcohol. That’s a slightly slower quench, but still able
to avoid forming that brittle structure. If you’ve cooled it slowly,
reanneal with the quench. If you didn’t cause that brittle structure
to crack, reannealing it with the quench fixes the structure. If you
worked it at all, though, and formed cracks, then you’re kinda out of
luck…

You can add silver if you wish, but any silver added will lighten
the color. It doesn’t take much silver to make a distinct difference
in the color.


#7

This may not be very helpful to YOU, Brent, but others may find it
so: The Finnish master jewelers working for Faberge commonly used an
18K alloy consisting of 75% Fine AU and 25% CU, nothing else.

Very careful annealing was necessary to avoid cracking and
inadvertent firegilding.

Purposeful fire gilding of this alloy produces an interesting
result…

If you heat the metal to dull red and let it air cool you will see
the copper oxide on the surface. Pickling will remove the oxide and
leave a very thin layer of purer gold. Burnish this gold surface and
repeat the careful heating to dull red, cooling in air, pickling and
burnishing 5-6 times. You will be left with a surface exceeding 20K
and having the same color as 20K gold, and it will be quite hard
from the heavy burnishing. This way, you can create a piece with the
look of high karat, but very durable and it’s still 18K (well, a
little higher).

That’s not YOUR goal, I know, but the 75/25 mix produces a lovely
red color.

Ever seen the museujm tour of the “Gold of the Incas”, all the
goblets and pieces presented as pure gold? They aren’t, never were.

Wayne Emery


#8
If you heat the metal to dull red and let it air cool you will see
the copper oxide on the surface. Pickling will remove the oxide
and leave a very thin layer of purer gold. 

Just don’t drop or try to bend it after air cooling it will
fracture.

James Binnion
James Binnion Metal Arts