Redken Acidic Bonding Curls Silicone-Free Leave-in Treatment is a treatment that works to provide heat protection, repair, and hydration to damaged curls. This treatment prepares hair for styling with heat protection against temperatures up to 450F. With Acidic Bonding Concentrate Silicone-Free Leave-In Treatment, curls are strengthened and provided with up to 96 hours of shine and definition*.