What's the deal with karat platinum?

[SaoriViola]

i was just online looking at some jewelry and one of the pieces was listed as "karat platinum".  when i looked it up it was being touted as "better than 950 platinum". the jewelry was also way cheaper than platinum jewelry should be...

[oldmancoyote]

Run... mile... opposite... direction...

Platinum purity is measured in thousandths. Full stop. I suspect it may be platinum (or rhodium) plated silver or worse.

[SaoriViola]

I just found this explanation:

"The combination of 58.5% platinum 41.5% cobalt and copper results in platinum with characteristics that are superior to 950 (95%) platinum. In rigorous laboratory corrosion and abrasion tests for tarnishing, Karat Platinum™ outperformed traditional 95% platinum, emerging from the tests without colorations or stains."

do you smell BS, 'cause i do.

[oldmancoyote]

The bull is considerably bigger than Trinkette's Red.

I could also suggest that the combination of 70% iron, 18% chromium, 6% molybdenum, 4% nickel and 2% manganese plus carbon traces is a wonderful metal in terms of corrosion, tarnishing and abrasion resistance. Probably better mechanical properties than any platinum alloy at low temperatures. I wouldn't say it's "superior to platinum" for jewellery all the same - it's usually called "stainless steel"...

[Diamondsbylauren]

Wow, it's news to me!!

[SaoriViola]

damn OMC, you just owned.  well played.  btw, what's trinkett's red?

[oldmancoyote]

Red is here. With special headdress.

[Mrs Mitchell]

It is stainless steel, isn't it?

Please set my lovely new diamond in stainless steel, I like to have a matching set.

Well, it would match my kettle and toaster...

[oldmancoyote]

Not quite, if you mean "Karat Platinum". It's a cobalt-platinum alloy with a high % cobalt, and the equivalent platinum content of gold in 14k gold. Given the excellent resistance to tarnish and corrosion of the normal jewellery platinum alloys, I can only assume it's a way of lowering the price (or increasing the margin, or both).

The "recipe" I gave above is top-quality corrosion-resistant stainless steel. Excellent metal, but a bit too hard for much jewellery work (it won't stretch or bend enough). It will look very much like platinum-cobalt (950/50), though.

[ah2bqat]

Woof!   OMC, you are definitely on your game today.  I had all but forgotten Big Red.

[Sparkly-OCD]

I found this:

"Our Karat Platinum™ is a unique combination metal made up of 58.5% Platinum. This piece is stamped 585Pt/415CoCu."

I thought it was a plating material.  Thanks for bringing this up SaoriViola.

[SaoriViola]

so interesting everyone!
i've also heard people say that there's a difference in 950 plat depending on what the 5% is made up of.  anyone have any info on that?

[oldmancoyote]

There is indeed. Iridium, Ruthenium, Palladium and Cobalt are the most used alloy metals for jewellery purposes. Rhodium is used for high-temperature resisting dies (such as those used in glass fibre manufacturing). Some notes on some of the four main alloys characteristics:

50 Iridium: most commonly used. Relatively soft, and usually needs a certain amount of cold working to harden it a bit.
100 Iridium: liked by many smiths as the best for hand fabrication. Harder than 50 Ir. Traditional (until the 1990s) US alloy, sometimes marked IRIDPLAT

50 Cobalt: Very hard, darker grey than Iridium; excellent for casting, since Cobalt gives the melt low viscosity. It can tarnish with exposure to high temperatures, and some smiths use this for decorative purposes. Otherwise it is sometimes rhodium-plated to make it bright white.

50 Ruthenium: Usually used for rings and other cold machined pieces, since it's bright white (not as much as Ir/Rh, but more than good enough) and quite hard. It's difficult to cast. This is the alloy used by a certain store with a famous blue box.

50 and 100 Palladium: Used predominantly in Japan - very soft and ductile, mainly used for casting.

If you want more info, here there is a very good overview of the above, with much greater detail and more alloys (including the thermo-sensitive alloys used for tension settings).

[SaoriViola]

you are a goldmine OMC, thanks for the info. very interesting!

[crypto_coyle79]

Which alloy does DBL use?

[joia]

Red is here. With special headdress.

Lovely Big Red.   I love him, but he still hasn´t learnt how to use his tiara properly  nevertheless  he still looks gorgeous to me.

[oldmancoyote]

crypto_coyle79: I think it's 950/50 Ir, but the only one that can answer precisely is