Gold Colors
You know, today gold is not just yellow. It can be different colors: white, rose, green, and even blue or purple.
White gold is very popular now. It can be 18-karat or 14-karat (but not 22-karat, it is yellow).There are two basic groups of white gold alloys: white gold with nickel and with palladium. Palladium costs more but it is better because some people have an allergy to nickel.
The laws in Europe don’t allow nickel alloys to protect people with allergies, 18-karat white gold jewelry made in Europe is more likely to have palladium white gold.
Much white gold jewelry is plated with rhodium.The Rhodium is a platinum group metal with a bright white color. The nickel alloys are grayer than the rhodium.
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Purple Gold is referred to as amethyst or violet gold. The process to make purple gold is to alloy gold and aluminium in a certain fixed ratio. Gold content is around 79% and is therefore qualified to be referred to as 18K gold.
Blue Gold is made as an intermetallic compound between indium and gold. The gold gets a bluish hue color.
Black Gold is possible using quite a few techniques today. Electrodeposition using black rhodium or ruthenium is the first method. Amorphouse carbon is also used at times, with the Plasma Assisted Chemical Vapour Deposition process. Controlled oxidation of carat gold containing chromium or cobalt can also be made to yield black gold. Ruthenium containing, electroplating solutions give a slightly harder black coating as compared to electroplating solutions that contain rhodium. The blacker the gold, the less wear resistant it would be.
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