Pure gold does not tarnish. Gold items less than 24 carat can show signs of tarnishing because the other metals in the alloy may react with oxygen or other compounds.
Gold jewelry and other items under 14 carat need periodic cleaning. Copper and silver are used in lower carat items. Perspiration, cleaning agents and perfumes can cause these to tarnish. Copper, when reacting with oxygen or other corrosive compounds, produces a green residue. Silver causes black discoloration. Black smudges may be left on the skin when wearing jewelry that is beginning to tarnish.
Polish jewelry often with a soft cloth to remove early tarnish buildup, perspiration or other compounds. Be sure the box, bag or other storage container used for gold is free of sulphur compounds. Some adhesives and fabric treatments, for example, create sulphur dioxide and other sulphuric gases, increasing the rate at which the lesser metals in gold alloy tarnish. Avoid handling gold items after using cleaning chemicals, washing dishes or preparing food. Gold items of lower carat can be plated with 24 carat gold, which prevents any tarnishing in the short term. With frequent wear, the underlying gold alloy is exposed over time and may begin to tarnish.