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Pouring white gold ingots


#1

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


#2

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


#3

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


#4
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