tldr; K18 is highly effective for repairing chemically processed or severely heat-damaged hair, often used instead of conditioner, but is considered expensive if damage isn't present.
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Best praise vs top criticism for K18 Leave-In Molecular Repair Hair Mask
“Oh no I'm so sorry! I have dark curly hair and get it bleached to do light fantasy colors a couple of times a year. I use K18 and alternate it with a heavy conditioner/mask (the last couple of times I used amika soul food and love it). Olaplex is great too, but it's a bit more involved than using K18.”
“I agree with the other person that responded; all of the curly people I know always need product to get definition and no frizz. That being said, it looks like you’ve bleached your hair, which always causes some damage. You could try a bond building treatment like Olaplex 3, K18, etc. and curly hair almost always needs moisture, so a deep conditioning treatment probably wouldn’t hurt either.”
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817 Reddit opinions analyzed • Last updated 2/24/2026