Hi to all those who asked about the white gold. (This may scan more
legibly if you copy and save to a word processing program.) The
following is only for small batches, unless you are well set up for
large scale melting.
Here are the white gold alloy recipes. You’ll need a fair bit of heat
when mixing these metals. Use oxy-acetyline with all the usual safety
precautions - good fume ventilation, protective dark goggles,
non-flammable environment and protection, the appropriate high
temperature silica crucibles, etc. The secret is to have the highest
melting point metal completely molten and liquid in the crucible
first, and then carefully add the second-most highest melting metal in
small pieces so that they are completely dissolved into the first
highest melting point metal, and so on… In other words, put in the
palladium first (it melts at 1550C) and get it molten before adding
the fine gold (which melts at 1064C), then add the nickel, then the
copper, then the silver, last of all the zinc which will flash quickly
and disappear. Keep the crucible moving a little so that the gold
roils around and heavier elements don’t settle, then pour as soon as
possible after the zinc has gone in. The zinc seems to serve no other
purpose except to ensure a smooth pour, but I’m no metallurgist, so I
could be wrong about that. All I know is what works in practice.
If you just throw all the metals in together cold, then start melting
them together, the lowest melting point metals such as the silver and
zinc will quickly melt and cover the higher melting point metals. Some
of these will deceptively surface-melt but most of the palladium and
pure gold and copper will simply form lumps of pure metal. The metal
manufacturers avoid this by using specialised furnaces and crucibles,
but if you are melting these up on the jeweller’s bench, you may not
have this sort of expensive equipment.
(Au = 24ct gold. Pd = Palladium. Ag = Silver. Cu = Copper. Ni = Nickel) Palladium White Gold Alloys: 18ct White: 75% Au + 10% Pd + 10.5% Ag + 2.5% Cu + 2% Ni 14ct White: 58.5% Au + 10% Pd + 28.5% Ag + 1.5% Cu + 1% Ni Nickel White Gold Alloys: 18ct White: 75% Au + 14% Ni + 5.5% Cu + 5.5% Zn (Zinc) 14ct White: 58.5% Au + 14.5% Ni + 20% Cu + 7% Zn or 58.5% Au + 15.3% Ni + 25.8% Cu + 0.4% Zn (Harder alloy) 9ct White: 37.5% Au + 17.5% Ni + 27.6% Cu + 17.4% Zn Palladium-Nickel White Gold Alloy: 18ct White: 75% Au + 15% Pd + 5% Cu + 5% Ni
It’s interesting to do small batches, but, in all honesty, the
refiners and assayers do it much better and will accept responsibility
for their product if it’s not quite right. Hope this helps, Rex.