K18 is one of the most asked-about products in our salon, and one of the easiest to use the wrong way. Use it properly and a small amount goes a long way. Put it on dry hair or follow it with conditioner, and you're washing money down the drain.
Here's exactly how to use it, how often you need it, and where to buy genuine K18 in New Zealand.
How to use K18 in 4 steps
- Shampoo and skip the conditioner – wash as normal, but leave conditioner out on K18 days.
- Towel-dry – hair should be damp, not dripping.
- Apply a small amount – 1–2 pumps for most hair, 2½–3 for long or thick hair. Start at the ends and work up towards the roots.
- Wait 4 minutes, then style – don't rinse it out. After 4 minutes, blow-dry or style as usual.
How often: every wash for your first 4–6 washes (especially after colour or bleach), then every 3–4 washes to keep your hair in good shape.
What K18 actually does
Most conditioners and masks coat the outside of your hair so it feels softer straight away. K18 works differently. It uses a peptide that works inside the hair to help repair the keratin chains that bleach, colour and heat break down. That's why it doesn't need rinsing, and why it doesn't need to feel heavy to be working.
It's best for hair that has been coloured, lightened or heat-styled a lot, but any hair type can use it.
Getting the most out of every use
- Less is more – K18 is very concentrated. Start small and only add more if your ends still feel dry once it has soaked in.
- Damp, not wet – if your hair is dripping, the mask gets watered down. Squeeze out the water with a towel first.
- Ends first – your ends are the oldest and most damaged part of your hair, so start there.
- Give it the full 4 minutes – set a timer before you reach for the hairdryer or brush.
- Keep using heat protection – K18 isn't a heat protectant, so still use yours before straighteners or curling wands.
How often should you use K18?
It depends on where your hair is at right now.
- Freshly coloured, bleached or very damaged hair – every wash for the first 4–6 washes.
- Once your hair has improved – every 3–4 washes, or whenever it starts feeling dry, rough or snappy again.
- Healthy hair you want to keep that way – every 3–4 washes is plenty.
If you wash your hair twice a week, that works out to roughly once every week or two for maintenance.
Using K18 on bleached or coloured hair
This is where K18 really earns its place. Lightening and colour are the biggest causes of damage inside the hair, so the washes straight after a colour appointment are the most important time to use it. Use it on each of your first 4–6 washes after colour, then drop back to every 3–4 washes.
Getting your colour done with us? Ask your stylist about adding K18 to your appointment when you book online.
Where to buy genuine K18 in NZ
K18 is popular, which means copies and grey-market products turn up on online marketplaces. Buying from a salon means you know it's the real thing, it's been stored properly, and you can ask a hairdresser if you're not sure how to use it.
- K18 Leave-In Repair Mask 5ml – the easiest way to try K18, and handy for travel.
- K18 Leave-In Repair Mask 15ml – a bigger size for regular use.
- K18 AirWash Dry Shampoo 118ml – refreshes hair between washes.
See the full range on our K18 page, or browse everything we stock in our salon hair products shop. We ship NZ-wide, and if you're wondering why salon products are worth it, read our take on salon shampoo vs supermarket shampoo.
Frequently asked questions
How long do you leave K18 in your hair?
4 minutes, then style as usual. It's a leave-in, so you don't rinse it out.
Can I use conditioner with K18?
K18's instructions are to skip conditioner on the days you use it: shampoo, towel-dry, then go straight in with K18. On the washes in between, use your normal conditioner.
Can I use K18 once a week?
Yes, for maintenance that suits most people. If your hair has just been coloured or bleached, use it every wash for the first 4–6 washes first.
Can I put K18 on dry hair?
It's designed for freshly shampooed, towel-dried hair. On dry hair it won't spread as evenly, so you'll likely use more product than you need.
How much K18 should I use?
1–2 pumps for most hair, 2½–3 for long or thick hair. Start small, as it's very concentrated.
Does K18 replace my hair mask?
Not necessarily. K18 works on repair inside the hair, while a nourishing mask adds softness and moisture. Many people use both, on different washes.
Is K18 worth the price?
Because you only need a small amount, and only every few washes once your hair is in good shape, it lasts longer than most people expect. If you're not sure, start with the 5ml mini and see how your hair responds.
