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White gold alloys


#1

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.


#2

Greetings All In having read your posting I instantly thought how
different the method you use is to the one I have been using. If
nothing else it shows how forgiving metal can be. Rex, please do not
take offence at this posting, it is meant as alternatives to use, not
as a correction to your posting. Input from a refiner would be
appreciated.

    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.. 

This is almost the opposite of what I’ve found to be useful. I had
occasion to speak to a refiner who had retired and his way of mixing
the metals was to put the Zinc on the bottom of the crucible and this
was followed by other metals in order of their reaction to oxygen.
This didn’t work for me.

In practice I found that by mixing the lower melting temp. metals
together first then slowly adding the gold and palladium until all
where liquid works well. There is an exception to this (isn’t there
always?) and that is Nickel, it resists being assimilated into the
alloy, so I usually melt it with a small amount of gold and copper to
get it to alloy more easily.

Alternately mix the lower temp. metals, pour into an ingot mould
(basically making a master alloy), then mix the higher temp. metals
Palladium, Gold, Nickel ect then reintroducing the alloy of low
melting metals.Mixing the lower metals together zinc silver and copper
is to get the zinc into the alloy and not the atmosphere. The reason
for not starting the higher temp. metals first and adding the lower
progressively comes from the fact that the final alloy will melt at a
much lower temp. than the higher temp. metals, so in effect the
metals are being over heated. Somewhere along the line I remember
reading that by overheating the alloy it will destroy or damage the
grain structure, which in turn may cause the resulting alloy to crack.

    , last of all the zinc which will flash 

This can be prevented to a large degree by using the above method for
melting, ie making a master alloy first and then adding the precious
metals. Carefully warming the zinc under the silver and some copper
will help stop the zinc being lost, as it won’t flash but as it fumes
it alloys with the other metals. At times I melt a small amount of
silver on one side of the crucible and then allow the zinc and copper
to touch it, this too can prevent large losses of zinc. There will
always be a certain amount of loss. Only by experimenting will you get
the mix/technique right for you, the reader.

   The zinc seems to serve no other purpose except to ensure a
smooth pour

A really good source of on alloying metals and the use of
zinc is the book " Santa Fe Symposium on Jewelry Manufacturing and
Technology 1989" Available through Rio Grande. Look in the section on “
Cadmium free gold brazing alloys” pages 179 to 207. You will have to
search for the sections involving zinc.

These days as time is much shorter for me, I tend to use the master
alloys made up by refiners and “just add gold”. The master alloys we
use have no nickel in them and I use nickel only if we need an alloy
that is used for shanks. Generally we use 3-5% Nickel as a maximum as
some people have an allergic reaction to nickel. Yes I realise even in
these amounts some people will react, but that is another string that
someone else may like to comment on.

In conclusion the main thing is to experiment with small amounts
until you find the right methods for you.

Happy experimenting

William Russell in Sunny Nth Queensland, blue skys and white beaches.


#3

Hi all

I need some advice on formulating white gold.

I usually hand fabricate my work using a natural alloy of 20k yellow
gold, which is 87% gold and 12.9% silver (0.1% ‘other’). My methods
and designs are therefore adapted to this fairly soft metal.

When a client wants white gold, I have been making it using the
following formula (by weight):

75% 24k gold
15% palladium
5% copper
5% silver

But I find the resulting metal to be quite hard, and difficult to
form. I suspect the formula I have was designed for white gold for
casting. Another problem with this recipe is that the white gold is
quite grey. I would prefer a whiter looking white gold. Can anybody
suggest a better formula for me?

Thank you!
Leslie Chapman
Fortymile Gold Workshop


#4
But I find the resulting metal to be quite hard, and difficult to
form. I suspect the formula I have was designed for white gold for
casting. Another problem with this recipe is that the white gold
is quite grey. 

You’re first issue is just what you’re used to working. Your 20K
yellow made with almost only just silver is not “fairly soft”.
Relative to most jewelry alloys, it’s about a soft as partially
melted butter. Any other alloy, with the possible exception of actual
24K gold or annealed fine silver, is going to feel hard to you.
Palladium white golds are fairly soft compared to most, and the mix
you’re using should fit that description. Palladium white golds are
also not known for being all that white. Usually described more as
brownish, but also can be greyish, as you note. The whiter ones are
generally alloyed with nickle, not palladium, along with copper,
usually a bit of silver, maybe traces of zinc or other grain
refiners, depending on the exact desired properties, color and
karat.

But if you think your current alloys are hard, be prepared for a
surprise. The nickle based white golds can sometimes be even harder
to work than mild steel.

That doesn’t mean it’s unworkable, but if you are used to that high
karat yellow, you’re going to have to get used to a very different
idea of what is workable or not. Alloying the white golds, though, is
often not quite as simple as the gold/copper/silver alloys. That may
include your palladium alloy, as palladium can give significant
problems when being alloyed or melted, and indeed, if you are making
up your own alloy, starting with pure metals including pure
palladium, you may be getting a final alloy that is harder than it
needs to be owing to impurities or oxides it may pick up during
melting. Palladium alloys are notorious for this, especially with
torch melting. Might I suggest that rather than starting with the
pure alloys and making your own, it would be more efficient and
probably not much more costly, for you to deal with any of the
standard metals refiners who sell not just fully prepared gold
alloys, but the alloying mixes themselves. You can buy “master
alloys” that will have everything already alloyed together except the
gold. Some of these mixes can be used for a variety of different
karat values depending only on how much gold you add, so they’re
pretty versatile. Talk to the suppliers about which of their alloys
will be best for your uses, as there are many different types. These
prepared alloys generally will work better than the ones you mix
yourself, as they can include carefully calculated traces of things
like grain refiners or deoxidizers which can result in marketly
better castings if you cast, or better working stock for fabricating.
Now, if to make your metal you want to be using your natural alloy as
the starting point, you may have to do some tweaking. Custom alloys
could be made for your purpose, but I suspect that may be no longer
as cost effective.

Consider sending some of your natural alloy to a refiner, either to
have them make up your desired final alloy, or trading it for an
equivalent quantity of pure gold as the starting point. Or just try
it. Some of the nickle alloys might not mind a higher amount of
silver too much. But talk to the metals suppliers for that.

Peter Rowe