<font color="0000ff">ladies,
got a good article on white gold
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White Golds</font>
What are they?
What are 'white golds'? Are they a special form of gold? Do they contain gold? These are typical questions often asked of us. Well, they are not a special form of gold (which is why you cannot get 24 carat white gold). Actually, they are true carat golds, just like yellow or red carat gold jewellery. They are gold alloys that look white rather than yellow. The white colour is achieved by careful choice of the alloying metals, which bleach the deep yellow of pure gold.
It is interesting to note that white golds for jewellery were originally developed in the 1920's as a substitute for platinum. Nowadays, they are a jewellery metal in their own right and currently very fashionable and desirable, particularly among the younger age groups. White golds are available up to 21 carat. They are often used to enhance diamonds and other gemstones. White gold bridal jewellery is increasingly popular.
Making gold white
Making gold white is similar to mixing colours in paints. Adding a red metal (copper) will tend to make gold red and adding a white metal tends to make gold paler and eventually white. Thus, all other alloying metals to gold, apart from copper, will tend to whiten the colour and so it is possible to make carat golds that are a reasonable white colour.
Whilst additions of any white metal to gold will tend to bleach it's colour, in practice, nickel and palladium (and platinum) are strong 'bleachers ' of gold, silver and zinc are moderate bleachers and all others are moderate to weak in effect.
This has given rise, historically, to 2 basic classes of white golds - the Nickel whites and the Palladium whites. The nickel-whites tend to have a colder white colour, whereas the palladium whites have a warmer colour. Good nickel whites tend to be hard and difficult to process. Good palladium whites tend to be soft, easy to process (but lost wax casting is more difficult) but are much more expensive, because of the price of palladium. Consequently, many commercial white alloys are thrifted in nickel or palladium and contain some copper; hence, colour is compromised. At the 8-10 carat (33.3 - 41.6% gold) level, gold-silver alloys are quite white, ductile although soft and are used for jewellery purposes.
For a fuller explanation of the metallurgy of white golds and their properties, see the companion article on Gold Jewellery Alloys.
White gold jewellery is often plated with rhodium
There is, as yet, no legal or industry-accepted definition of what constitutes a 'white' colour in golds and hence the trade description of 'white gold' may not mean an alloy that is 'ice white' or 'detergent white'. For good technical and economic reasons, many commercial white golds are not a good white colour (usually a yellow-brownish tint) and are often rhodium-plated to improve appearance.
<u>Rhodium</u> is one of the platinum family of metals and has a high reflectivity and good metallic white colour and is hard with good wear properties. A thin electroplated coating is often applied to white gold jewellery to improve its white appearance.
This is legally allowed in many countries, including those with Hallmarking regulations. Such a coating, if not subjected to undue abrasion, should have a lifetime of, typically, 3 years before it wears through to reveal the gold alloy underneath.
For many consumers, the colour of rhodium has become the norm for the colour of white gold, because that is what they are used to seeing on jewellery described as white gold!
See Whiteness Guidelines for Jewellery Manufacturers >>
The nickel skin allergy problem
Unfortunately, many people (around 12-15%), the female population especially, are allergic to nickel in contact with the skin and this gives rise to a red skin rash or irritation. This problem applies to costume/fashion jewellery, white gold and steel jewellery, zippers and fasteners and other body piercings.
The European Union countries have enacted legislation (under the EU Nickel Directive) valid from the 20th January 2000 that limits nickel release from jewellery and other items in close and constant contact with the skin. Thus, in Europe, nickel white golds are being phased out and being replaced by palladium white golds, although low nickel alloys that meet the nickel release requirements of the Directive are still in service. This does not guarantee that a nickel-sensitised person will not suffer an allergic skin reaction if wearing jewellery made from such conforming, nickel-containing alloys!
Japan and China have taken a similar position on nickel. The USA is taking a more relaxed approach, requiring jewellery to be labelled as nickel-containing. Many other countries have not taken a stance on nickel in jewellery and nickel white golds are still widely sold.
Much jewellery is now advertised as 'non-allergenic' or 'nickel-free'. For more information on the approach taken to the EU legislation, see the article in Gold Technology, No 28, Spring 2000, "Nickel gets under your skin" . Fuller information on the EU Directive on nickel can be found in the article, "The European Directive on nickel in jewellery: Update" in Gold Technology No 29, 2000.
Alternative white golds
As palladium white gold is more expensive, there is a demand for cheaper alternatives that are nickel-free. Many new, patented alloys are coming to market, most of which rely on manganese additions as the main whitener. Some are palladium-free and others are low palladium alloys. They tend to be hard and more difficult to process. Many of these alloys are not a good white colour and require rhodium plating. They may suffer cracking and tarnishing problems too. Compositions of such alloys are not published. For further information see article, "White golds - Meeting the demands of international legislation" in Gold Technology no 27.
Buying white gold jewellery
As stated above, some white gold jewellery sold in the EU may contain some nickel and still conform to the EU Directive on nickel. Sensitised people may find that they react to such jewellery. Conforming to the EU directive is no guarantee that these alloys will not cause an allergic reaction. Check with your retailer that the alloy is nickel-free! Rhodium-plating should provide some limited protection, but remember electroplatings are often porous and will, in time, wear away!
<font color="ff0000">White gold jewellery wearers can be disappointed to discover that their jewellery has gone off-white, <u>even a yellow-brown tint</u>, as the rhodium plating wears through (some cheaper jewellery may well be distinctly yellow-brown in colour). </font>
There is currently no legal requirement in many countries for the retailer to tell purchasers if the jewellery is rhodium-plated. This applies to some platinum jewellery as well as white gold. Purchasers should always demand to know if their jewellery is rhodium-plated. If the jewellery is rhodium-plated, then you cannot know how white (or not) is the gold alloy underneath. A good quality white gold, with good colour, should not need to be rhodium-plated but may well be to conform to a consumer expectation.
If the rhodium plating does wear through, the jewellery can be easily re-plated through your local retailer and the good colour restored.
pop by to see u'll..hehehe 
