I have never worked with rose gold and am wondering if there
are any special issues I need to consider? I've heard its a real
bear.
18K rose has an inherent risk, if it’s an alloy of only copper and
gold. At this ratio, it is almost a 1:1 ratio of copper to gold atoms
(gold is about three times denser than copper, so with three times
the weight of gold (18K) you have a copper atom for each gold. What
can happen is that while cooling, the gold and copper segregate out
into separate layers, each one atom thick. This is called an ordered
array structure, and differs from the normal random mix of copper and
gold in solution in each other. The problem is that the ordered
array structure is very brittle. So in working with this alloy, you
need to prevent the formation of the ordered array structure. Two
main methods are used. One, is that you use a rose alloy that isn’t
just copper and gold, but rather, substitutes some zinc, or
preferably, silver, for at least a bit of the copper. This lightens
the color, but need not be so much that it’s not still a nice rose
color (zinc would be used if you’re casting it, since it’s used as a
deoxidizer).
The other method, and a good idea with any rose gold in any case, is
simply to not let the metal cool so slowly as to allow the formation
of the ordered array. forming this structure (which is not stable, and
dissipates, at higher temperatures), simply means cooling the alloy
quickly enough after soldering or annealing, that it doesn’t have
time to form that ordered array structure.
In short, you always quench rose gold alloys. Now, sometimes rose
golds can tend to be “hot short”, meaning they’re a bit short on
strength when hot. The result is that when quenched, you can crack the
metal if you’re not careful. 46irst, quench the metal once the red
glow has just barely disappeared, a temperature of around 900F. You
need to quench it above about 750 to 800 degrees or so, to prevent
the ordered array, but you don’t want to quench it too hot, or it can
crack from the stress. Also, to further reduce the stress of
quenching, you can quench in alcohol, rather than water. It’s a
gentler quench, cooling the metal more slowly than a water quench,
but still fast enough to keep the metal soft and workable. In
quenching in alcohol, just be sure not to drop the jar, and immerse
the metal quickly so it’s under the surface while quenching. That
keeps it from igniting the alcohol. And, should you accidentally
ignite the alcohol, just calmly put the lid on the jar. Don’t panic
and drop the jar. Spilling burning alcohol all over your bench pan
can get exciting and dramatic very quickly.
Properly annealed and quenched, you’ll find rose golds quite nicely
workable. They’re harder than yellower alloys, but not unacceptably
so, and still easier than some of the white gold alloys.
Perhaps the biggest problems with rose golds are that finding
solders that match well in color can be difficult. The best color
matches tend to still not be the best working solders. I’ve yet to
find one I actually like. Many times, people just make sure the seams
are very well fitted and tight, and then use just a yellow gold
solder. With clean enough work, the color difference may not be too
noticeable. Of course, with a laser welder, this can be helped a
lot, though even then, if you’ve got an older laser without pulse
shaping or argon shielding, you might sometimes have problems with
welds cracking…
Hope that helps.
Peter Rowe