Choosing the Right Developer Volume
Developer (hydrogen peroxide) activates hair color and controls the level of lift. 10 volume (3%) deposits color without lift - ideal for toning or going darker. 20 volume (6%) is the standard for most permanent color, providing 1-2 levels of lift. 30 volume (9%) offers 2-3 levels and is used for high-lift applications. 40 volume (12%) provides maximum lift of 3-4 levels but carries the highest damage risk. Always consider hair condition and porosity when selecting developer strength.