Hair bleaching

[3] The bleaching agent used by the Roman women was composed of a solution of ashes from burnt nuts or plants.

[4] Diodorus Siculus, a 1st century BC Greek historian, described in detail how Celtic people bleached their hair: "Their aspect is terrifying...

Their hair is blond, but not naturally so: they bleach it, to this day, artificially, washing it in lime and combing it back from their foreheads.

[4] In Sir Hugh Plat's 1602 work Delightes for Ladies, the use of oil of vitriol (sulfuric acid) to bleach black hair to chestnut is described as: "Take one part of lead calcined with Sulphur, and one part of quicklime: temper them somewhat thin with water: lay it upon the hair, chafing it well in, and let it dry one quarter of an hour or thereasbouts; the wash the same off with fair water divers times: and lastly with sope and water, and it will be a very natural hair-colour.

After the movie's success Hughes's team established a chain of "Platinum Blonde clubs" in several cities and offered a $10,000 prize that would go to any hairdresser who could copy Harlow's shade.

Creatives such as Alexander McQueen, Anna Sui, and Pat McGrath had models like Linda Evangelista bleaching their eyebrows.

Persulfate salts, in combination with hydrogen peroxide or alone, are known for their ability to degrade organics after activation with heat, transition metals, ultraviolet light, or other means that produce the sulfate radical.

[17] Industrial bleaches that work by reduction (such as sodium hydrosulphite) react with a chromophore, the part of the molecule responsible for its color and decrease the number of carbon-oxygen bonds in it, making it uncoloured.

This process might be reversed to a certain extent by oxygen in the air, such as yellowing of bleached paper if left uncovered.

In contrast, hydrogen peroxide chemically alters the chromophore by increasing the number of carbon-oxygen bonds.

Around 72 percent of customers who agreed to be involved in a study and have European ancestry reported in a recent 23andMe research that the sun lightens their hair.