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Why Does Jewellery Turn Skin Black? Jewellery FAQ IndexChard 24 Carat Home Page

18 Carat Gold

9 Carat Gold
Cheap Jewellery Makes Skin Turn Black
Quite often people ask us why a particular piece of gold jewellery leaves a black mark on their skin, sometimes all jewellery has this effect. We have already answered the question in different places on our site, if people would take the time and trouble to look. For example, we have a page titled "Why 18 Carat is Best", which answers this and many other questions. In fact if you read that page, you hardly need to read or learn much more about gold alloys or gold jewellery. To make life easier, however, for those who haven't got the time to read any of the other 2,000+ pages, packed with information, on our websites, we have created this page to explain the discolouration problem more specifically.

Eighteen Carat is the Best!
It's as simple as that! We have never known anybody suffer this discolouration problem with 18 carat gold jewellery, it only happens with lower grade alloys, such as 9 carat, 10 karat, 14 carat, 14karat, and possibly 18 karat.

18 Carat versus 18 Karat
We'll come back to this later.

Base Metal
The base metal content, mainly copper, in low carat gold alloys can and does get attacked by acids in perspiration and in the atmosphere. The result is oxides and other salts which rub off onto skin and fabrics leaving black or green marks. The lower the gold content of the alloy, and the higher the proportion of base metal, the more likely the alloy is to be attacked by acids and other chemicals. Conversely, the higher the carat quality and the lower the base metal content, the less likely there will be any reaction with chemicals.

The Solution to the Problem
The solution is simple. Stick to high carat gold alloys such as 18 carat, 22 carat is also OK. If you are reading this page because you have a discolouration problem with a low carat alloy, we suggest you ask the jeweller you bought the item from for his explanation, and whether he is prepared to offer a solution to your problem. If you don't get any satisfaction, we further suggest that you should dump that jeweller, and deal with a high quality, reputable outfit instead, such as the people who brought you this page! You might even save money into the bargain. Most of our prices are considerably below those charged in retail jewellery stores. We offer you quality jewellery, quality information and advice, and still charge less than most of our competitors. If you continue to buy from the same old sources, don't say we didn't try to help you.

So What's Wrong With 18 Karat?
Eighteen carat should theoretically contain 75% gold, unless it's American eighteen karat, in which case it may legally be only 17 1/2 carat, and therefore contains only 72.9% gold. It may not seem very much difference, but if you were to study a graph of the properties of gold alloys, you would find that at about 75% gold, the alloy becomes practically inert to attack and corrosion by most chemicals, 18 karat just fails to reach to standard, whereas 18 carat is above the critical point.

American Alloys
Theoretically, these should be the same as English or International standards, however as the USA is still, to the best of our knowledge, using a law about two centuries out of date, from when testing was not quite as accurate as today, American jewellers are allowed a half carat tolerance. Fairly naturally they take this tolerance and use it to legally supply sub-standard alloys, and this adds to their profits. Because of this, if an American jeweller wishes to promote his jewellery more honestly and accurately, it becomes necessary for them to indicate this in some way, so that they add the word "plumb" after the fineness. This in itself we find amusing, as it comes from the Latin word for lead, which is the last thing you would wish to find in a gold alloy!

Because platinum is usually sold in high purity alloys, it too is resistant to chemical attack, and will not cause discoloration problems. It's best to go for 95% pure platinum, the cost difference between it and lower alloys such as 90% and 85% is not really worth saving.The only problem with platinum is its colour, great if you like grey, but if you prefer yellow, then you will need to stick to gold.

Green?, Blue?, Any Other Colours
We also get asked about jewellery turning skin green. The answer is the same as above.
We had never heard of jewellery turning skin blue until today. The answer is as above. Of course it could be that your ring is too tight!

But My Jewellery Was Expensive!
Cheap jewellery is not always the same as inexpensive jewellery, just as expensive jewellery is is not always the same as quality jewellery.

You may wish to visit some of our other pages:-

Why 18 Carat is Best
Density of Gold & Other Metals
Allergies to Gold Jewellery
Hardness & Durability of Gold Alloys
What is White Gold?
White Gold Turns Yellow
Platinum Information
Gold Alloys - What Is A Carat?

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