No, there are two key limits: 1. On natural hair, you can lighten a maximum of four shades (for example, from chestnut to light blond); 2. If the hair is already colored, you can redo the same shade or darken it, but it's impossible to lighten without bleach.
The oxidation coloring process doesn't remove pigments (natural or artificial) already in the hair fiber. It simply oxidizes existing pigments and permanently alters them. On natural hair, it excels: lightening up to four tones, darkening, or adding highlights. But on previously colored hair, it's trickier. "The chemical molecules in the oxidation reaction lack the power to break down artificial pigments," explains Frédéric Mennetrier. "They layer on top of the previous color. Darkening works well since darker pigments dominate, but lightening may do nothing—or worse, create unflattering results like uneven tones or brassy reflections."
Insights from Frédéric Mennetrier, colorist at Atelier Blanc and L’Oréal Professionnel expert; Rodolphe Lombard, colorist at Couleur par Rodolphe salon; and David Merveille, Schwarzkopf consultant hairdresser.
