To bleach something, is to remove or lighten its color, sometimes as a preliminary step in the process of dyeing; a bleach is a chemical that produces these effects, often via oxidation. Common chemical bleaches include "chlorine bleach", a solution of sodium hypochlorite (NaClO), and "oxygen bleach", which contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate or sodium percarbonate. Bleaching powder is calcium hypochlorite.