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Red gold problem


#1

I heated a red gold piece to find the solder seam and didn’t quench
it because it had a few small diamonds in it. When it was too hard to
saw through, I read through the archives and belatedly saw the
postings about the awful crystal structure that red gold takes on if
it cools through 700 degrees. I then attempted to reanneal and
quench, risking the diamonds, but it doesn’t seem to have annealed it.
Is the damage done at 700 degrees permanent, or am I being too
tentative with my heating and quenching because of the stones? Linda


#2
   I  heated a red gold piece to find the solder seam and didn't
quench it because it had a few small diamonds in it... 

I solder platinum right next to diamonds practically every day. I
generally use 1300 solder for repair and fabrication. You must flux
the diamonds heavily to exclude any oxygen. I use Batterns. It’s a
yellow liquid available from most suppliers. Apply with a needle type
dispenser bottle after warming the piece. Keep the flame on the area
as you slowly add more flux. By the way, Batterns, as well as any
boric acid/ borax flx will tend to leave a soft grey stain on
platinum, so, be careful. For rose gold, you will see that it is the
answer. If you are skeptical, try it on a chipped or broken stone
first. Diamonds can take much more heat than any other stone if done
with care and common sense. DON’T TRY THIS WITH ANY OTHER MATERIAL.
BORIC ACID FLUX WILL PERMANENTLY ETCH CORUNDUM/ RUY AND SAPPHIRE. Good
luck! Ken Weston


#3

Ken, I have used alcohol and boric acid daily for years on all types
of stones and never etched one.Perhaps a heavy mixture of boric acid
will etch more readily.What ratio of boric acid to alcohol do you
use?I don’t flux platinum at all as I was taught it did not need to be
fluxed.Does 1300 platinum solder melt at 1300 degrees F.?

Regards J Morley
Coyote Ridge Studio


#4

I have used alcohol and boric acid daily for years on all types
of stones and never etched one.

I agree, I have never had problems using boric acid. What I have
found though is many jewelers use borax instead of boric acid. They
are both white powder and look the same. However, they respond
differently. Borax is a mineral and can fuse to stones under high
heat.

Borax alone or mixed with boric acid can be used as a flux, but
should not be used to protect stones from heat. Use only Boric Acid
for this.

Brad Simon


#5
   Borax alone or mixed with boric acid can be used as a flux, but
should not be used to protect stones from heat.  Use only Boric
Acid for this. 

Both borax and boric acid are borosilicates. both fuse to glasslike
liquids at higher temperatures. Both, when molten, will dissolve
oxides of nany metals. Because borax melts at a lower temperature,
however, it becomes an active solvent for metal oxides at a lower
temperature, and consequently, as it dissolves oxides, will be come
"burned out" sooner. Boric acid is less active as a solvent when at
the same temp as borax, and thus will withstand more heating, and
higher temps before becoming saturated and no longer able to protect
the metal.

Of those stones we can readily subject to heat, which amounts to
diamond and corrundum, plus a few others, the most common other than
diamond, corrundum, is aluminum oxide. Both borax and boric acid, when
molten, can start to dissolve some of the aluminum oxide, thus etching
the stone. It doesn’t actually fuse to it. Just dissolves some of
it. Borax, being active at a lower temperature, is more dangerous in
this regard, but over heated boric acid will also attack corrundum
(ruby or sapphire). The damage is related to both temperature and
time. Brief heating may cause not damage at all. Many of the
commercial soldering fluxes have additional agents in them to make
them even more active solvents for oxides. These, like batterns or
the various white paste fluxes, will also attack corrundum if given
the chance. The white paste fluxes containing fluorides, being the
most active at the lowest temperatures, are the most dangerous to
these stones. Plain boric acid, with the highest temperature
tolerance and the least activity at a given temp, will be the safest.
But it’s not automatically totally safe. And the lack of any
protective coating too, can be dangerous, if the flame you’re using
is a reducing one (what we usually use for soldering gold and silver).
Just as that reducing flame aimed at mildly oxidized metal can clean
it up, the same flame aimed at your ruby will reduce the surface
aluminum oxide to aluminum. The result is an unattractive stain on
the stone’s surface.

Peter Rowe