![[c] marcy vanity logo 2026](https://marcyvanity.com/wp-content/uploads/2026/10/cropped-C-marcy-vanity-logo-2026-185x45.png){kind=logo}
Olaplex No. 3 and K18 are the two bond repair treatments everyone talks about for bleached, colored and heat-damaged hair. They’re used very differently. Here’s how to choose.
Heads up: This post has affiliate links. If you buy through them, Marcy Vanity earns a small commission at no extra cost to you. As an Amazon Associate I earn from qualifying purchases.
Quick verdict
| Olaplex No. 3 Hair Perfector | K18 Leave-In Molecular Repair Mask | |
|---|---|---|
| Type | Pre-shampoo treatment, rinse out | Leave-in mask, no rinse |
| How to use | On damp hair, leave 10+ minutes, then shampoo and condition | After shampoo (skip conditioner), leave 4 minutes, then style |
| Best for | Bleached or colored hair, weekly care | Very damaged hair, fast routine |
| Price | Mid-range | Higher, but a tiny amount per use |
Olaplex No. 3 Hair Perfector
What it does: a weekly at-home treatment made to help repair broken bonds in hair damaged by bleach, color and heat.
Pick it if: you color or bleach your hair and want a simple weekly step before you wash.
Check today’s price on Olaplex No. 3 →
K18 Leave-In Molecular Repair Mask
What it does: a leave-in mask you use after shampoo. You skip conditioner, let it sit a few minutes, and style as usual.
Pick it if: your hair is very damaged and you want a treatment that doesn’t add time in the shower.
Check today’s price on K18 Hair Mask →
Which one should you buy?
Bleached or colored, budget-conscious: Olaplex No. 3.
Very damaged, short on time: K18.
Fine hair: K18 is weightless. Use Olaplex No. 3 and follow with a light conditioner.
Want more moisture too: pair either one with a hydrating hair mask.
Shop hydrating hair masks on Amazon →
Tips to protect damaged hair
- Use a heat protectant every time.
- Turn down your hot tools.
- Sleep on a silk or satin pillowcase.
- Get regular trims to remove split ends.
FAQ
Can you use Olaplex No. 3 and K18 together?
Many people alternate them. Follow each product’s directions, and don’t overdo treatments.
How often should I use K18?
Follow the label. Many people use it for the first few washes, then less often.
Is Olaplex No. 3 a conditioner?
No. It’s a pre-shampoo treatment, so you still shampoo and condition after.
Keep reading
- The Best Hair Masks on Amazon for Dry, Damaged Hair (Most Under $20)
- Olaplex No. 7 Bonding Oil Dupes: What $7 Actually Gets You
- The Best Heat Protectant Sprays on Amazon (Mostly Under $15)
Pin this comparison, and follow Marcy Vanity on Pinterest for more hair repair tips.
Save this for later 📌
