Formulated for use with crème permanente and demi permanente formulas, these dedicated developers provide superior viscosity and create optimal bowl-and-brush application. Crème Permanente developer To match or deepen color, use 10-volume crème permanente developer. To cover more than 30% gray, use at least 20-volume. To lighten natural hair color Levels 4-10 (Light Brown - Lightest Blonde): 1 Level 10 Volume 2 Levels 20 Volume 3 Levels 30 Volume 4 Levels 40 Volume 5 Levels Double 40* Volume (When mixed with high-lift blondes) To lighten natural hair color Levels 1-3 (Black - Medium Brown): 1 Level 20 Volume 2 Levels 30 Volume 3 Levels 40* Volume NOTE: For additional lift, formulate 1-2 Levels lighter than the desired Level. Create a deposit-only formula by mixing with equal parts crème demi permanente hair color. Will not lighten and covers up to 50% gray. Mix equal Parts Clairol Professional Creme Permanente Hairircolor with Clairol Professional Creme Developer.