An image of yellow metal hits to the mind when the subject of discussion is gold. Once it was impossible to believe that gold could be white, red, and pink even black too but thanks to engineering research that made everything possible. Now you can buy several colors in gold including classical yellow tone.
Naturally gold occurs in bright yellow color with its attractive metallic luster though colored gold can be produced alloying precious yellow metal with other elements in different proportions.
How gold is colored?
Basically three metals – gold, silver and copper are used to develop colored gold. Different ratios of different metal cause different colors in its classical yellow tone. Apart this, colored gold can be developed using inter-metallic compounds or using surface oxide layering technique which is mostly utilized to create black gold.
How gold is measured?
Gold is measured in karats. 100% pure gold is graded as 24karat (or 24K) metal. Other grades are 22K (92%), 18K (75%), 14K (58%), 10k (41%) and 9K (38%).
Different Colors of Gold
White gold is developed creating an alloy of gold and at least one white metal, mostly nickel, manganese or palladium. Sometimes copper, silver or platinum are also mixed to enhance gold’s durability and weight. White gold metal contains 90% of gold and 10% wt of nickel or silver. People who don’t like to buy impure gold, prefers rhodium plating on gold jewellery because it does not originate skin irritation as white gold (having copper, nickel or manganese) does.
Rose Gold & Pink Gold
Rose gold is made by alloying gold and copper. Rose gold ranges from red to pink tones and is used to design specialized jewellery. These all shades are created using different percentile of copper in gold. though ideal ratio is either 75% gold and 25% copper or 50% gold and 50% copper. Rose gold is used to design high end musical instruments and artistic pieces.
Green gold is created mixing silver in gold. The new green metal contains ratio of 75% gold and 25% silver or it can be manufactured alloying 75% gold, 23% copper, and 2% cadmium.
Minor percentage of white metals like silver, manganese and copper turns yellow gold into grey gold. Either one of three or all of three above metal can be alloyed in new grey metal varying on requirements.
Newly invented purple color gold is liked by fashion designers to create something very unique and different. Alike other colored gold, purple gold is combination of gold and aluminum in a ratio of 79:21.
Alloying gold and indium creates blue gold but it’s not defined as gold because it contains only 46% gold with 54% indium.
Making black gold is quite different and demands specialization of the field. Black gold is made by using three techniques namely — electroplating using black rhodium, patination (applying sulfur and oxygen on yellow gold) and chemical vapor deposition utilizing amorphous carbon. In addition, sometimes controlled oxidation method is also used to produce black gold.