some metal facts you might not know

[oldminer]

Gold and platinum are alloyed with less costly metals when making the karat quality used for jewelry. Most platinum jewlery is 95 to 90 percent platinum with the balance an alloy. Some new platinum products are 50% platinum and 50% less costly metal although some is alloyed with palladium which is hardly "cheap", but less costly than gold or platinum.
Gold is alloyed with many different metals, all of which cost way less than gold. All alloys are substantially lighter, a lower specific gravity, than pure gold or pure platinum.

When we hear that 18 karat gold is 75% gold we rarely give it a second thought. Or if we hear of 50% platinum being made of 1/2 platinum and 1/2 another metal we don''''t think a lot about it.

Here''''s the strange part. Metals are alloyed by WEIGHT, not by VOLUME. The alloys for gold and platinum are MUCH lighter than gold or platinum. It takes quite a bit more volume of alloy metal to mix in to make any karat of gold or platinum than one might think.

By volume, 14kt gold, is quite a bit less than 50% gold content. By volume, 50% platinum is far less than 1/2 platinum and 1/2 alloy.

It is the classic situation of mixing feathers with lead to get a 50-50 ratio of content. A few drops a lead and a container full of feathers makes 50% of each by weight, but the composite lead/feathers when examined buy VOLUME is nearly all feathers with just a spot of lead mixed in.

Platinum and gold when pure don''''t tarnish. It is always the alloy that tarnishes anyway. That'''' s why 14kt gets a patina faster than 18kt. The amount of alloy content that can tarnish is a lot higher in 14k than 18k. The new platinum/palladium mix may not tarnish because pure platinum and pure palladium don''''t tarnish. I suppose when mxed, they still will not oxidize.

Anyway, food for thought. I always loved making karat gold when I did shop work many years ago. Glowing, flowing metals, the hissing of the torch, the smell of the burning and the bright metal when it finally cooled. When you see the amount of alloy in a 14kt gold unmelted pre-mix, you''''d really be surprised.

 

[Iiro]

Hi Dave

15 years deacades ago my I tried to exlpain this to my tutors in goldsmith school, but they said no-one thinks like I do, better to stop that!



Now this is my favorite story to anyone in our business.

 

[kenny]

Should we consumers get better informed on what is being alloyed with the gold or platinum we buy and insist that it is "the best".

If so, what is the more or most desireable metal(s) and why?
Or is this a can of worms, or too complicated for our mortal minds?

 

[oldminer]

Funny how the mind can be trained just to assume something. I'm one of those who always wants to know, "What's inside?" Almost every business has a game plan or a game being played. Its entertaining to explore these things. No harm done.....or at least, I don't want to harm anyone. Every story has another point of view.

As far as spreifying alloys, it is rarely necessary. Many people are allergic to the nickle that was once common in white gold. A lot of white gold today has no nickle, or very minute nickle content.

For the most part, don't be overly concerned. Those who make tension settings use very specific alloys and treatments to get the metal effect they desire. To them, it matters.

 

[FireGoddess]

This is quite fascinating. I always mistakenly assumed that the percentages were by volume - and thus 14kt was 50% gold...not less. Very interesting! Thanks for writing this!

 

[Garry H (Cut Nut)]

Imagine Dave, in Aussie, Britian and South Africa 9ct gold (37.5%) is common for earrings and chains etc.
Imagine the amount of gold in the melt compared to the silver and copper.

I just asked my workshop manager to tell me next time they are doing a melt and I will try to make a little movie for yo''all.

 

[blitz]

Several months ago, I evaluated a white metal ring, with diamonds. I felt it was of Asian decent. The stamp within the shank was "320". I tested with available acids. With platinum acid, very small specks of whitish response. No reaction to 18 or 14. At the time I listed it as "unknown"

Two weeks ago I was sent a pair of white metal earrings with SC diamonds. Feather weight and similar reaction to the above acid tests. This time I had permission to submit to David Fell in Los Angeles. The xray revealed Silver 50.07%, Nickel 37.43%, Paladium 8.29%, Copper 3.26%.

I am trying to track down the manufacturer of these jewelry items. Does this ring a bell with any of you?

Thank you,
Jennifer

 

[perry]

Old Miner is right. Alloys are made by weight (or more correctly mass; but on earth, you can think of it as weight).

He is also right that it is the alloying elements that tarnish in most jewelry.

The tradeoff is that the alloying elements in most cases provide better material properties (pure platinum or pure gold is rather soft - and not suitable for jewlery).

I would not worry about the amount of other metals for alloy contents of 10% or less; but you might want to know for some applications where the alloy content is higher than 10%.

Here is a link to some technical information on most normal Platimum jewelry alloys, and the benifits/tradeoffs:

www.noble.matthey.com/pdfs/English/37.pdf


I am intriqued by the 50/50 Platinum Palladium mix. I would expect it to be somewhat soft - but it may not "scratch tarnish" like normal 90-95% platinum does (requiring polishing to bring back the bright look). It will be interesting to see how and where it is used and its properties.


Here is a comment I found on another website, and an interesting lead:

www.stillwaterpalladium.com/jewelry_950_palladium.html

"The search has been on for a workable white alloy that stays white, is hypoallergenic and priced more agreeably than the often prohibitive platinum. Alloys emerging include mixtures of 50/50 platinum and palladium, ‘585 platinum’ with cobalt and copper and several alloy combinations in between."

However, they then go on to state that they have chosen 950 Palladium because it stays white, and does not need rhodium platting (or repolishing); and that it makes a great replacement for white gold items.

Interesting....

Lastly; how could I be true to the forum if I did not show some 950 Palladium rings (with the same claims as the other website):

www.ganoksin.com/borisat/nenam/950Palladium-intro.htm

Enjoy.

Perry

 

[oldminer]

There are may coming platinum/palladium combinations coming out. All have smalkl amounts of other metallic alloys to increase hardness, etc. Really, there is no 50/50 metal, but a small part of these are always going to be alloys.

During WWII there were many palladium rings made as platinum was not available. Palladium is a decent metal for white jewelry although when alloyed normally it does gray out some over time. It is not workable like platinum for hand made items, but it can be cast nicely. It is just about as heavy as gold when used in jewelry, so it is lighter than platinum. Sometimes a jeweler can just tell by the heft of an item what metal it is made of.