Here's what I found on the net regarding white gold:
WHITE GOLD
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.
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.
Rhodium 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.
Because the natural color of white gold is light grey, rhodium plating makes white gold whiter. Plating increases luster in greyer jewelry, and prevents oxidation. Since rhodium eventually wears away, white gold should be replated with rhodium every 12 to 18 months. However, palladium and silver alloys are of a higher quality than nickel and are sometimes not coated with rhodium.
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!
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!
White gold jewellery wearers can be disappointed to discover that their jewellery has gone off-white, even a yellow-brown tint, as the rhodium plating wears through (some cheaper jewellery may well be distinctly yellow-brown in colour).
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.
WHITE GOLD VS. PLATINUM
Platinum is often compared to white gold, although the two metals are very different. Platinum is a naturally white metal. White gold is, actually, yellow gold which has been alloyed (mixed) with other metals. White gold contains silver or nickel and very little or no copper. Standard yellow gold has about an even mix of silver, nickel and copper. White gold is plated with rhodium in order to keep its platinum-like luster. This plating tends to disappear with time and wear, causing the gold's natural color to appear. How long will it take? There is no simple answer. It depends on the thickness of the plating and the precise conditions under which it was applied.
Pure gold, 24k, is too soft for reasonable jewelry use. A pure gold ring would bend and become dented very quickly. When we speak of 18k and 14k gold, there are standards for the amount of pure gold used for each. In the case of 18k the gold purity is 75 percent fine; with 14k gold the purity is 58.3 percent fine. The alloys are used strengthen and provide the desired color gold for the jewelry.
Some persons can not wear gold jewelry. Skin discoloration is caused by skin secretions or perspiration containing chlorides. When these come in contact with the copper and silver alloys, they produce dark colored salts; copper sulfate or silver chloride. Since 18k gold possesses 75 percent fineness, it is not affected as easily as lower karat gold. Changing to white gold or platinum should eliminate this problem.
Platinum is the only precious metal used in fine jewelry that is 90% to 95% pure, largely hypoallergenic and tarnish-resistant. Platinum jewelry will be marked 900/950Pt, 900/950Plat. or Plat. The most used metal representing the remaining ten percent or five percent of the alloy is iridium.
Platinum is the most valued of the precious metals. Its value normally exceeds that of gold. Its beautiful silver-white color will not tarnish. It is unaffected by common household chemicals and, unlike gold does not get damaged by chlorine, bleach, or detergents. It is tougher than all precious jewelry metals, but, it still must be alloyed with stronger metals to prevent it from bending. We use iridium because of its toughness and durability.
Another minor difference is the weight. Platinum is heavier (specific gravity: 21.4) than gold (specific gravity: 19.3). When you alloy white gold the difference is even greater. The difference on a small ring is small but on a large piece, it is very noticeable.
It takes very special skills and tools to work in platinum. Furnaces producing approximately 3250 degrees Fahrenheit are required. Whereas , the melting point of gold is1550 degrees Fahrenheit. And, methods differ from those employed in working with gold.
The cost of platinum jewelry is generally higher than gold because of the rarity of the metal, its purity and the intricate process of working with it. But, the beauty and enchantment it exudes from jewelry, in addition to its properties, make it one of earth's finest treasures.
Scratches on Gold versus Platinum?:
When we talk about scratches on hand worn Platinum or Gold jewelry, we are not referring to large eye visible scratch marks (like a cat’s claws made on my mother’s favorite dress). Instead we are referring to hundreds of “micro-scratches”, no one of them visible to the eye, but in combination over time, all jewelry worn on the hand will eventually be covered in small “micro-scratches”, which will give a dull appearance.
Platinum, which is slightly more malleable, but more dense than Gold, will take on a frosted appearance. Platinum does not micro-scratch the same as Gold, but actually “furrows” instead. The furrowing effect pushes metal to the sides instead of removing material. Visualize the Red Sea parting or a farmer furrowing his field! On the other hand, when Gold is micro-scratched, the Gold metal is actually removed. Sometimes these micro scratches can leave white gold looking a bit yellowish.
VS. TITANIUM
Titanium is a white metal, but unlike gold it is used in jewelry in almost its pure form (approximately 99% pure). Titanium is extremely long wearing. Its natural color is a gray color.
Titanium is very lightweight, so a titanium ring will feel much lighter than an 18kt gold ring and much lighter than a platinum ring.
Titanium is also 100% hypoallergenic.
Titanium also has a unique property which allows the titanium to be colored to bright colors such as blue, purple and black. See more information about colored titanium rings here.
Unlike other metals (such as gold, platinum and silver) titanium is a difficult metal to work with from a jewelry perspective. Titanium is a very hard metal which wears down jewelry making tools very quickly. Titanium also cannot be soldered (joined by heat).
Soldering is used in the manufacture of the majority of traditional jewelry items. Because titanium cannot be soldered, the method of making some jewelry items is restricted when using titanium.
For example titanium cannot be used to make a prong setting for an engagement ring. That is why you will see that many titanium rings have parallel bands rather than tapering bands and why you will not see titanium rings with prong settings.
For the metal itself titanium is generally less expensive than 9kt white gold. However, because titanium is difficult to make jewelry with the labor costs of titanium can make the price of a titanium jewelry a little higher. Though white gold will still normally command a higher price than titanium.
Other considerations:
1. Titanium and white gold are available in a wide range of rings
2. Titanium is hypoallergenic vs. Some people experience skins reactions to gold
3. Most white gold rings can be resized vs. Titanium rings cannot be resized
4. White gold can be used to make virtually any ring style vs. Titanium cannot be used to make prong and bezel settings (though we can use gold prong and bezel settings with a titanium band)
5. Titanium can be made in bright colors such as blue or purple vs. white gold cannot be made in bright colors
6. White gold normally will need to be rhodium plated each 12-18 months. vs. Titanium in its natural color does not need to be re-coated.
7. Both titanium and white gold rings can be re-polished by a local jeweler.
8. Both titanium and white gold can be re-textured by a local jeweler.
9. Titanium is normally less expensive than white gold
You can check out my sources. They have visuals on the difference between white gold & platinum. Am still checking out other sites. 'Will update you later.
2006-09-25 23:16:22
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answer #10
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answered by Mye 4
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