K18 Leave In Molecular Repair Mask 50ml

The full-size bottle of the leave-in treatment K18 built its name on. It is a four-minute, no-rinse step that goes in after shampoo and instead of conditioner, aimed at hair that has genuinely been through it — bleached, repeatedly coloured, or heat-styled to the point of feeling porous and crunchy.

The actives

• K18PEPTIDE (sh-oligopeptide-78) — a patented bioactive peptide, formulated to work inside the strand on the keratin chains that colouring and heat break down.
• Hydrolysed wheat protein and wheat starch — smaller proteins that condition the surface while the peptide works.
• Behentrimonium chloride and cetearyl alcohol — the conditioning base that gives the treatment its slip.

How to use it

Shampoo, skip the conditioner, and towel-dry thoroughly — conditioner leaves a film that gets in the peptide's way, and excess water dilutes it. One to three pumps depending on length and density, starting at the ends and working up. Leave four minutes. Do not rinse. Then style as normal.

Worth knowing

Best used for four to six consecutive washes after a salon service, then as needed to maintain. At 50ml, this is the size to buy if you are committing to that full run rather than trying it out.