Olaplex and K18 are the two names clients ask about most when their hair feels weak after bleach, color or hot tools. Both are marketed as repair treatments, both are used in salons and at home, and both have loyal fans. They are not the same technology, though, and knowing the difference helps you recommend the right one, or use them together.
Key takeaways
- Olaplex is built on a patented bond-building ingredient, bis-aminopropyl diglycol dimaleate, which targets broken disulfide bonds.
- K18 is built on K18Peptide, which the brand says reaches the innermost layers of the hair to reconnect broken keratin chains.
- Olaplex’s best-known home step is a pre-wash treatment. K18’s is a 4-minute leave-in mask applied after shampoo.
- They are not mutually exclusive. Many stylists use both, following each product’s directions.
How Olaplex works
Olaplex launched in 2014 around one patented molecule, bis-aminopropyl diglycol dimaleate. Hair gets much of its strength from disulfide bonds, the sulfur-to-sulfur links between keratin proteins. Lightening, color, chemical texturizing and heat break those links. Olaplex says its Bond Building Technology repairs broken disulfide bonds at the molecular level to restore strength.
In the salon, Olaplex steps are added during chemical services. At home, the classic step was Nº.3 Hair Perfector, a pre-wash treatment left on before shampooing. Olaplex is now replacing it with Nº.3PLUS, which it describes as a 3-minute pre-wash that works on all three types of hair bonds. After the treatment, you rinse, shampoo and condition.
How K18 works
K18 arrived in 2020. Its patented K18Peptide is designed to fit hair’s keratin structure. According to K18, the peptide penetrates past the cuticle to the innermost layers of the hair and reconnects broken keratin chains, restoring strength and elasticity.
The signature product is the Leave-In Molecular Repair Hair Mask, and the routine is specific (K18 how-to):
- Shampoo, but do not condition.
- Towel-dry the hair well.
- Apply 1–3 pumps from ends toward roots, depending on length and density.
- Leave it on for 4 minutes. Do not rinse.
- Style as usual. K18 suggests using it for 4–6 washes in a row, then as needed.
Olaplex vs K18 at a glance
| Olaplex | K18 | |
|---|---|---|
| Core technology | Patented bond builder (bis-aminopropyl diglycol dimaleate) | Patented K18Peptide |
| What it targets | Broken disulfide bonds (Nº.3PLUS: “all three” bond types) | Broken keratin chains in the inner hair |
| Signature home step | Nº.3PLUS pre-wash, about 3 minutes, then rinse, shampoo and condition | Leave-in mask after shampoo, 4 minutes, no rinse |
| Where it fits | During chemical services in the salon, plus a full home line | Salon treatment plus a short home routine |
| Oil in the line | Nº.7 Bonding Oil | Molecular Repair Hair Oil |
Which one should you recommend?
Bleached and highlighted blondes
Protect the hair during the lightening service itself with your salon bond builder, then send the client home with a repair step. Both brands target this client. Choose by routine: Olaplex’s home step comes before shampoo, and K18’s comes after shampoo, so one may fit a client’s wash day better.
Fine hair that goes flat easily
Many clients with fine hair like leave-in steps that do not add weight. K18’s mask is a light leave-in. If a client prefers nothing left in the hair, a rinse-out pre-wash treatment may suit them better.
Heat damage and daily styling
Repair does not replace protection. Pair either treatment with a heat protectant such as K18 HeatBounce and keep irons at the lowest effective temperature.
Using both
Because the brands describe different targets, some stylists layer them, for example a pre-wash bond treatment, then shampoo, then K18 on towel-dried hair. If you do, follow each product’s instructions exactly. K18’s mask must go on after shampoo and before any conditioner.
What repair treatments cannot do
No treatment makes split ends grow back together for good. Treatments can improve strength, elasticity, softness and shine, but badly split or broken ends still need a trim. Set that expectation with clients so the treatment gets credit for what it does.
Olaplex and K18 products at OBB
Stock changes, so call or text before you come in. We currently list:
- Olaplex Nº.7 Bonding Oil (Jumbo)
- Olaplex Nº.4C Bond Maintenance Clarifying Shampoo
- Olaplex Weightless Nourishing Mask, Nº.10 Bond Shaper Curl Defining Gel and Volumizing Blow Dry Mist
- K18 Molecular Repair Hair Oil
- K18 Damage Shield Protective Conditioner and K18 AirWash Dry Shampoo
See all treatments, masks and oils in Hair Care, or call or text (949) 591-5304 and ask about sizes and case pricing.
FAQ
Is K18 better than Olaplex?
Neither is simply better. They use different technologies and different routines. The right choice depends on the hair, the service and which routine the client will actually follow.
Can I use K18 right after Olaplex?
Yes, as long as you follow both sets of directions: rinse out the pre-wash treatment, shampoo, then apply K18 to towel-dried hair without conditioner.
How often should I use K18?
K18 suggests using the mask for 4–6 washes in a row, then as needed, typically after clarifying.
Do bond treatments work on relaxed or permed hair?
Both brands position their products for hair damaged by chemical services. For timing around relaxers and perms, follow the chemical service manufacturer’s instructions first.
Sources
- OLAPLEX, Nº.3 vs. Nº.3PLUS
- K18, How to use K18 and Our science
- Wikipedia, Olaplex (company history and patented ingredient)
Brand names belong to their owners. OBB is an independent beauty supply store and is not affiliated with Olaplex or K18.
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