Gold Content in Watches
Part 2 of 4

Red Gold, White Gold, Green Gold and Rose Gold

Harder alloys of gold begin to have different purposes in watchmaking once other metals make up 25% of the weight of the "gold" and substantially more of it's volume.  The following descriptions of the qualities and liabilities of various 18 karat gold alloys may be used a as a guide to the qualities and liabilities of 14, 12, 10 and 9 karat gold alloys. Obviously the content of non-gold metals BY WEIGHT is much greater proportionally but the general features are the same. These descriptions are meant as a rough guide to understanding gold alloys using 18 karat forms as examples.

Using 18 karat red gold as an example we can see how this works. 18 karat red gold has approx. 1/4 of it's weight in copper and 3/4 of it's weight in gold. Because gold is 3.1 times as dense as copper the amount of copper in 18 karat red gold by volume is greater than that of the gold. Red gold is a good subject for discussion as well, because many people are allergic to copper metal directly on the skin and so 18 karat red gold produces rashes in some people who wear wristwatch cases made of this material. Pocket watch cases are usually not worn directly in contact with skin and so the allergy problem is greatly reduced.

"Black Hills Gold" that is red in color is often a natural alloy of gold and copper. Inside a watch, 18 karat red gold might be used for decorative jewel cups because its color might be interesting to the maker decoratively. Copper adds considerable hardness to gold, pure copper has been readily available for thousands of years and the two metals alloy well together. Solid 18 karat red gold gears are often used in watches with gold trains because such gears are self-lubricating. Brass and steel gears are often plated with various karat gold not only to protect from oxidation but to provide a degree of lubrication as well. For this reason many of the gears (or wheels) used in pocket watches with solid gold trains were made of 18 karat red gold. Many 18 karat alloys of gold are available using other metal alloys to produce a wide range of different hardness and colors.

18 karat white gold is a very common jewelry material and is often used in watch cases and bracelets. By weight it is usually 75% gold, 3% silver, 12.5% palladium and 9.5% copper. This makes white 18 karat gold about the costliest to make because palladium is very expensive. With such a large amount of palladium in the gold it is also a very hard form of gold and thus wears well. Only 18 karat green gold is harder amongst common forms. White gold has only 12.5% copper and silver combined and these metals can cause allergic or poisonous reactions in many people, so this form of 18 karat gold is one of the least allergenic. 18 karat white gold polishes well and also resists scratching. It's weight and subtle coloring makes it a popular case material for high-end watches. White gold is also one of the two most dense colors of gold.

18 karat green gold is one of the least common alloys of gold and is available most widely in "Black Hills Gold" products. The composition of 18 karat green gold makes it the hardest form of 18 karat gold normally available. 18 karat green gold is an alloy using 75% gold, 2% silver, 3% palladium, 5% copper and 15% chrome. Chrome has a blue cast in its pure form and it is a very hard metal on its own. Chrome causes some severe allergic reactions so the use of green gold in watch cases has been limited but there have been some watch cases made from this material by Longines, Ardath, Elgin, Hamilton, Waltham and Patek Philippe. Although 18 karat green gold will polish to a mirror-like finish and it will resist scratching very well, the color is not very fashionable and the possibility of allergic reactions has limited its use in watch cases.

18 karat rose gold is an alloy usually produced by mixing 75% gold, 16% copper and 9% silver together. This type of gold alloy is very fashionable and thus is frequently used in jewelry and watch cases. Rose gold has often been used in solid 18 karat watch gears as well. Were it not for one physical and two psychological factors that make yellow gold the most popular, rose gold would likely be the most popular. As it stands in today's market, rose gold is slightly less popular than white gold. Rose gold has a very high copper content and this can cause some allergic reactions. Although it is not as common to have allergic reactions to rose gold as with red gold, there are many more reactions than there are with white gold. In addition, silver is actually poisonous and rose gold contains much more silver than white gold. These physical factors make rose gold slightly less popular than white gold in the market.