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| White Gold |
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| message from Tranh on 12 Dec 2000 |
Would any of you tell me how to make white gold?
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| PHILLIP PRATT replied to Tranh on 13 Dec 2000 |
Sure-you contact David Fell (or any other jewelry metal supplier) and order
white alloy! It is usually a mix of nickel and zinc, but sometimes paladium
is used. I have never tried to mix my own white the way I have for green
(silver only) or rose (copper mostly) or yellow (mix of silver and copper) .
White gold is a more finicky metal than yellow. Different suppliers have
different recipes for their alloy, so if you are casting or fabricating,
you need to specify when you order. Mix in appropriate proportions with 24K
and you are good to go. Marggi
Tranh wrote in message ...
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| Peter W. Rowe replied to PHILLIP PRATT on 13 Dec 2000 |
When nickel and zinc, there is also copper. Usually, more copper than nickel
for standard alloys. The "superwhite" ones have more nickel, but they still
need almost as much copper or else they become unworkably brittle. Paladium
white golds can have copper, but don't always have it. It's not needed, and
makes the color darker. But without copper, the alloy is a lot costlier, and a
lot softer too.
Peter
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| sunny replied to Peter W. Rowe on 16 Dec 2000 |
Is there any book that show the data of alloy used
to produce different property gold alloy.(color, or working property)
so you don't have to try all the recepe yourself.
Like the Machinery's hand book (Machinist Bible)
where they show the chart
sunny
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| "Buck Rogers replied to Tranh on 13 Dec 2000 |
It is very rare that you find pure gold.
9 carat gold is only 9/24ths (37.5%) gold. The other 62.5% consists
of other metals.
18 carat gold is 75% gold, the other 25% being other metals.
22 carat gold is 91.66% gold, the other 8.33% being other metals.
The amount of other metal you put in, and the type of metal you use
determines the colour of the finished product.
Add a reddish metal, like copper, and you get red gold. Add a white
metal, like silver, and you get white gold.
Simple, really.
You can see the same effect with coloured modelling clay. Mix red
with yellow and you get orange. Mix white with yellow and you get a
paler yellow.
There are numerous recipes for white gold, each using different
combinations of metals.
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| Peter W. Rowe replied to "Buck Rogers on 13 Dec 2000 |
simple, yes. but the above recipe won't quite give you a white gold. While
silver is a very white metal by itself, it has relatively low "whitening"
ability in gold alloys. A 9 or 10 karat alloy of only silver and gold will
still be a pale yellow, often called a green gold (for more greenish yellows,
cadmium is sometimes added to green golds).
The usual metals added to gold alloys to give white golds are either nickel or
palladium. Palladium white golds can be just gold and palladium, but usually
theres some copper, and occasionally some silver and zinc too (usually, when
zinc is added to gold alloys, it's main purpose is as a deoxidizer to reduce
casting porosity. It also somewhat lowers the melting point, and makes the
color of yellow/rose golds slightly paler. Only small amounts are used in
yellow golds. More can be used in white golds)
Nickel based white golds are more common in the U.S. (but not so much used in
much of europe, since nickel is toxic, and in some alloys, not sufficiently
inert, and the EU now has stringent regulations regarding nickel in jewelry
golds). Nickel by itself is a powerful whitening agent in gold alloys, but when
used by itself, makes a very hard and brittle alloy that's difficult to work
with. Most white gold alloys contain at least as much copper as nickel, and
usually some zinc too, as a deoxidizer (some fancier casting alloys don't use
zinc, but use things like silicon or other deoxidizers. They work better for
casting, and less well if you're pouring ingots and rolling/drawing down the
metal. Silver is seldom added to nickel white golds, though I know some
goldsmiths who claim it makes a softer white gold thats better for setting.
Here are a couple standard nickel based white gold casting alloys.
14K, " Handy and Harmon satin white" 58.33% Au, 22.1%Cu, 8.77%Zn, 10.8%Ni
18K, 75%Au, 7.0%Cu, 4%Zn, 14%Ni
Hope this helps.
Peter Rowe
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| "Buck Rogers replied to Peter W. Rowe on 16 Dec 2000 |
Ok, I'm not a metallurgist. I was just illustrating the point with a
white metal.
I live in the UK, so I'm affected by the EU Nickel Directive, which
states:
Nickel may not be used:
1. In post assemblies which are inserted into pierced ears and other
parts of the human body during epithelization of the wound caused by
piercing, whether subsequently removed or not, unless such post
assemblies are homogeneous and the concentration of nickel - expressed
as mass of nickel to total mass - is less than 0.05%
2. In products intended to come into direct and prolonged contact with
the skin such as :
- earrings;
- necklaces, bracelets and chains; anklets, finger rings,
- wrist-watch cases, watch straps, and tighteners
- rivet buttons, tighteners, rivets, zippers and metal marks, when
these are used in garments if the rate of nickel release from the
parts of such products coming into direct and prolonged contact with
the skin is greater than 0.5 micrograms/square centimetre/week.
3. In products such as those listed in point 2 where these have a
non-nickel coating is sufficient to ensure that the rate of nickel
release from those parts of such products coming into direct and
prolonged contact with the skin will not exceed 0.5 micrograms/square
centimetre/week for a period of at least two years of normal use of
the product.
Furthermore, products which are the subject of points 1, 2 and 3, may
not be placed on the market unless they conform to the requirements
set out in those points.
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