Chem 101: Direct dyes
As the key pigments in temporary and semipermanent color, direct dyes have been around for a long time, but todayâs sophisticated color formulators are using the technology to achieve effects far more dramatic than your momâs ârinse.â
Direct dyes are pre-synthesized, so the color is already fully formed, requiring no oxidation, no developer.
According to Martin Uellner, Goldwellâs category manager, R & D Color & Perm, due to their often-larger molecular size, itâs difficult for direct dyes to penetrate the hairshaft.
âMost of them act more on the outside of the hair, leading to low durability,â he notes. âTheir benefit is they are very bright and intense.â
Uellner says the dyeâs tendency to fade can be suppressed by a special penetration agent, like the one used in his companyâs Elumen line. Direct dyes in the classic semipermanent color are normally cationic, but Goldwell uses anionic (acidic) direct dyes in Elumen which, says Uellner, donât cluster so they can penetrate easily. An electrostatic attraction also anchors them to the hair, he says.
In the fabric-dying world, negatively charged direct dyes are somewhat repelled by negatively charged fabric, until salt or an ionic agent is used to create a positive charge, allowing an ionic bond to form between the two. The difference with hair color is that the pH of the base formulation is creating positive-charged hair, which attracts the negative-charged dyes.
Direct dyes, whether used as the central pigment as in Elumen and Keuneâs Color Contrast or as part of a combination oxidative and direct technology as in Wellaâs Magma or Schwarzkopfâs Igora Vibrance, are for creating intense results. Pick a conventional permanent or demi formula when you want more natural shades.
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