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Pouring white gold ingots

Hello all,

I’m in a bit of a spot working with white gold (18k yellow - 15%
Palladium). My problem is probably the way in which I am melting and
pouring the gold into an ingot for rolling.

I initially made the gold at 20% palladium but found it too hard and
prone to cracking, so I added 18k yellow gold to drop the palladium
% to 15. When melting and pouring the gold into the ingot mold I am
getting a bubbling on top of the ingot which continues for a second
or so after the pour. This of course results in an ingot which has
pits and beads all over the surface. Cannot be good. I know I am
doing something wrong but just don’t know what.

The gold does seem to have a high melting point, which may indicate
that the palladium is not well alloyed. The metal will not melt with
Propane, takes a while to melt with Mapp gas and seems to go liquid
easily enough with Oxy-propane. Is the borax flux to blame ? …
something keeps bubbling and fizzing on top after the pour. It has me
stressing as my daughters wedding approacheth… Any help or advice
much appreciated (and needed)

Thanks in advance
John Bowling

you had better get on the phone to daniel ballard at pmwest
[preciousmetalswest.com] from your story my imagination can come up
with too many variables to fix what you already have started, you
should consider starting over with daniels suggestions

goo

First combine some powdered charcoal and sal ammoniac in a 3:1
proportion, and store it* air tight* - as the sal ammoniac is
humectant (it draws water out of the environment). When adding the
metals toalloy into a dedicated well borax glazed and red hot
non-graphite crucible ( and don’t use the same crucible for sterling
as you do for white gold - nickel based particularly- or other
non-Pt group metals. try to keep one crucible for each alloy with the
exception of low copper content/ high karat yellow golds ) use as
much borax as you would ordinarily and about 1/2 tsp of the
charcoal/sal ammoniac mixture per oz-oz and 3/4. Stir with a graphite
rod to remove any obvious impurities and just to mix well. You should
be keeping the flame on the metal as you pour and ensure the mould is
lubricated and hot as well…

the sal ammoniac can be used straight into the crucible but it works
best with the charcoal as an admixture and if you do use it straight
remember to wear an appropriate mask as the fumes are quite strong
and irritate mucous membranes readily.

As for the alloy that you have already poured sounds like it got
some ferrous metal in it somehow- you can grind it if you have the
facility to do so, and then use a minimum 40 lb. magnet to remove the
paricles of steel or iron ( or whatever it is that has gotten into
the mixture apart from the nickel in the original white gold scrap-
provided it was a standard, non-Pt alloy). The bubbling at the end
sounds like something contaminating the alloy and tolerating high
heat actually burning off with the fairly low temp Oxy/Fuel gasses
you are using… Try Mapp and Oxygen or acetylene and O2…Propane and
oxygen aren’t appropriate for Pt group alloys in any quantity-
perhaps in a quick solder to another metal in a workpiece but not for
melting more than a few grams- even then MAPP is better than propane
even with that O2 boost.

By the way, sal ammoniac is available cheaply in block form at a
stained glass supply- just crush wrapped in freezer paper, a few
thicknesses of newsprint or a piece of thin kidd leather, that you
can wash off easily and reuse after containing the crushed sal
ammoniac. Sometimes a good general hardware or weding supply that
deals in soldering equipment may sell it as a tinning agent- just
read the label as long as it’s 96% or better sal ammoniac it will
work well, though with a pure cake or pound of it from a chemist ( it
is available online from a number of chemical supply houses and os
not considered hazardous materials so the posting will not reflect
that additional charge…). but all said, the small 4 oz. cake
available at the stained glass supply will last about a year kept
well sealed and if you use it regularly for any alloy that you wish
the yield to be bright and tough but malleable enough for rolling by
hand… rer

First combine some powdered charcoal and sal ammoniac in a 3:1
proportion, and store it* air tight* - as the sal ammoniac is
humectant (it draws water out of the environment). When adding the
metals toalloy into a dedicated well borax glazed and red hot
non-graphite crucible ( and don't use the same crucible for
sterling as you do for white gold - nickel based particularly- or
other non-Pt group metals. try to keep one crucible for each alloy
with the exception of low copper content/ high karat yellow golds )
use as much borax as you would ordinarily and about 1/2 tsp of the
charcoal/sal ammoniac mixture per oz-oz and 3/4. Stir with a
graphite rod to remove any obvious impurities and just to mix well.
You should be keeping the flame on the metal as you pour and ensure
the mould is lubricated and hot as well. 

Not if you are working with palladium as the poster is palladium can
combine with the carbon in charcoal to make palladium carbide, which
is hard and brittle.

Try Mapp and Oxygen or acetylene and O2..Propane and oxygen
aren't appropriate for Pt group alloys in any quantity- 

BS, Acetylene can also a way to cause carbide formation in platinum
and palladium soldering and melting operations.

Propane works just fine with Pt and Pd.

James Binnion
James Binnion Metal Arts

Hello, I’m working with an 18k palladium white alloy ( or trying to ) it’s been cracking and cracking I’ve re melted it quite a few times and added some 18k yellow ( about 20%) at some point , I was already setting the stone and my bezel exploded like glass it cracked pretty bad , it’s not my first time with pd white and I make my alloys at home ( this time it where scraps I had sitting in the shop but all from alloys I had made and used before ) I’m way over my dead line and I need to remake the bezel but I just can’t get the metal past a few spins of the roller before it’s starts cracking , I’ve tried everything that has worked in the past and a few things that I’ve read ( that go against everything I know ) and still can’t get beyond a few spins of the roller and cracks come all over my ingot ,so if I have some how contaminated my alloy , I melt with propane oxigen, use only borax and a dedicated ceramic crucible , no graphite rod or crucible , So my question is is there a way ( without refining back my metals ) of making my metal alive again? I’m desperate but refining is not a possibility in my country at this moment .

Nandalek,

It’s my understanding that palladium when heated near melting temp, will absorb oxygen and this has been my experience also. It becomes very porous, like a sponge. If you originally made your own 18k alloy without a cover gas like argon, your metal is probably contaminated. Refiners will use argon gas to cover the metals so no oxygen will be present. I’m pretty sure it would be hard to be able to reuse the metal without refining. I’m unaware of any other options. I did do fabrication work in 950 palladium for a while and used a tec welder with argon gas to do sizing where the joints showed and 20k white weld to solder the non showing joints. It was a tricky metal to work with in many ways.

If alloyed properly 18k white-pd is a very nice metal to work with. It was one of my favorite metals to use in my custom design business. It could be rolled and fabricated, cast, and stone setting was very nice. I bought my metal already alloyed by the refiner, and never had a problem like what you described. Although It appears that Hoover & Strong no longer manufactures it.

Tjones

An Album of my work

Tjones,

Is the argon coverage needed only when first making the alloy? I plan to work with white gold-palladium at some point. Will I be able to melt it and pour into an ingot mould in my studio without any argon?

Hi.
Pd and Silver are both notorious gas scavengers.
With Silver it can be counteracted by adding carbon to the slag or a highly reducing flame, but Platinum group metals do not like that, they are too fond of carbon.

So any Pd alloy with decent purity will soak up oxygen from the air.
Most will be expelled during solidification, but it will be porous and generally not workable.

It should be melted in vacuum or inert atmosphere.

Regards Per Ove

Could this porosity be more frequent in casting than in pouring ingots?

Early on, I choose not to do my own alloying of the metals that I’d be using in my business, relying on a refiner to make sure that the metals were done correctly. I do not have direct knowledge of the actual process of alloying palladium. Whether it’s melted in a vacuum or
covered in an inert atmosphere (argon gas). I assumed that the refiner would use the inert atmosphere, but I shouldn’t have assumed.

“So any Pd alloy with decent purity will soak up oxygen from the air.
Most will be expelled during solidification, but it will be porous and generally not workable.”

This was my experience with 950 Pd, and why I used the welder with the argon gas, or kept the temperature well below the melting threshold.

If you are planning to make your own alloy, then I’d suggest you do a lot of research. Palladium has a much higher melting temperature than gold and must be treated like the platinum family alloys. Contamination of the platinum family metals, ie palladium is a big concern. I feel that normal equipment used for gold and silver are not going to give the best results.

The white gold alloy that I used, is mainly gold at 750, and then palladium as the bleaching agent to make it a white metal. I don’t know the exact amount of the palladium. With this metal I did not need to use the inert atmosphere (argon gas) or a vacuum for any of the typical operations, such as casting, pouring ingots, welding, soldering, fusing etc. I approached it as if I was working with 18K yellow. I use oxygen and natural gas and typical jewelers torches.

Because of the higher melting temperature of the 18k palladium white gold, it was great to fabricate designs using the metal. It also was malleable when annealed.

I have to emphasise and adjust this quote:
“So any Pd alloy with decent purity, when melted, will soak up oxygen from the air.
Most will be expelled during solidification, but it will be porous and generally not workable"

It will not to my knowledge soak up gases when solid, it is as we know extremely inert and a beautiful material.

Regards Per Ove

One more thing. When you say you approached it as if it were 18k yellow gold, is it applicable to the moulds as well? Will a Durston steel ingot mould work with Pd white gold? Or will it contaminate the Pd?

This is not my first time with this alloy ( I always use it for white 18k ) and although a bit more delicate than yellow I’ve never had this issue , save for a time years ago that I used a graphite stirrer ( and learned the hard way ) worst of all in that ocasión it was in a monumental billet and I had to refine the whole thing , but here ( as always I’ve been super careful and yet it seems to be spoiled , I will probably have to refine the gold out of it and start again te problem here is time and the fact that refining and buying Pd here in Mexico are both very difficult ( and to expensive )

Andreit,

18K pd white gold will work with your moulds, and the palladium in the metal will not be contaminated by the typical uses that I listed. That’s not saying that 18k pd white can’t be contaminated, as shown by the trouble Nandalek is having with his metal.

As I said, I’m not a refiner and haven’t tried mixing my own alloy in a long time. But I was told that sometime trace elements are added to the mix that will act as a catalyst to help the metal flow better, and then burning out in the melting process. This was given as a reason for always using a mix of 50% new metal along with old metal (for example the casting button). I don’t know if a catalyst is add when palladium is added to the gold in the making of the white alloy, but I always thought it was a good idea to mix the old with the new.

There are many ways a metal can be contaminated in the melting process. Things that come to mind are; contaminated crucible, carbon introduce into the mix, too much oxygen in the flame, old solder on the metal, etc… But if the old metal has been contaminated it won’t help adding new metal to it.

Tjones
An Album of my work

1 Like

Agreed Thomas, so today I went ahead and I quartered it with fine silver and recovered the gold , it remains to recover the palladium from my nitric solution , but I’ll start from scratch and I’m sure it will work this time , as you mentioned it must have gotten contaminated on the way either by carbon or oxigen, thank you all for the advice .