Hair serums with the weight printed on the bottleFree shipping over $45All prices in USD
Northline

The whole idea

The weight scale

Every product carries a number from 0 to 5 for how much a single application leaves behind on the strand. It is printed on the bottle, shown on every card and stated on every product page, because it is the one specification that decides whether a hair product works for you or sits in a cupboard.

Weightless

0

Rinses out, or dries down to nothing you can feel. Shampoos, conditioners and water-light mists sit here — nothing in this band can weigh hair down, whatever your hair is like.

Shop weightless

Medium

3–4

You will feel this one on the strand. Mid-lengths and ends only, on medium to thick hair — or on fine hair as a wash-day treatment and nothing more.

Shop medium

Rich

5

Heavy by design, for coarse, curly and colour-worn hair that drinks it. On anything finer it will look greasy within a day — that is not the product failing, it is the wrong number for the hair.

Shop rich

Against your own hair

Your ceiling

The number on the bottle is only half of it. Fine hair shows weight far sooner than coarse hair does, so the useful question is not “is this heavy” but “is this heavy for me”. These ceilings are deliberately conservative. You can always work upward; walking a greasy day back takes a wash.

Fine / thin

up to 2

Strands you can barely feel between two fingers, and volume that has dropped by the evening. Stay at 2 or under, keep everything off the root, and use half of what the bottle suggests before you use all of it.

15 of 20 products sit at or under 2.

Medium

up to 3

The default. 3 is comfortable on wash day and 1–2 on the days between. Mid-lengths down.

17 of 20 products sit at or under 3.

Thick / coarse

up to 4

Carries weight well and usually wants more than the label suggests. Work up to 4 before you reach for 5.

19 of 20 products sit at or under 4.

Curly / coily

up to 5

The one hair type the top of the scale is built for. Apply to soaking-wet hair, in sections, and do not rake it through once it has dried.

20 of 20 products sit at or under 5.

Read this part

What the number is not

It is not a measure of how well something works. Weight is what a formula leaves on the strand, nothing more. The Bond Repair Serum does the most structural work in this catalog and sits at 1; the Overnight Repair Oil sits at 5 and is mostly oil. Higher is not stronger, and it is certainly not better.

It is not a statement about you. There is no such thing as being able to “handle” a 5. The ceilings above are about hair diameter and density, which are facts about hair, not about the person it is attached to.

It is not a medical or industry standard. We made it up. It is a shared unit invented so that the products in one catalog can be compared honestly against each other, and it does not transfer to anyone else’s shelf. If it ever becomes a standard, that will be because it was useful, not because we said it was official.

It says nothing about your scalp or your health. Everything here is a cosmetic. Nothing on this site regrows hair, treats hair loss, or is a remedy for a scalp condition. If something about your scalp is persistent, sore or spreading, that belongs with a doctor rather than with a bottle.

The whole catalog

Every product, by weight

WeightMarkProductUsePrice
0CL-02Bond Repair WashEvery wash, on bleached or coloured hair$24.00
0CL-03Clarifying WashOnce every 3–4 weeks$22.00
0CN-01Daily ConditionerEvery wash$22.00
0CL-01Daily WashEvery wash$22.00
0SC-01Scalp ExfoliantOnce a week$28.00
1SR-04Bond Repair SerumDaily, or on every wash day$36.00
1SR-07Colour Guard UV SerumDaily in summer, before sun exposure$30.00
1ST-01Heat Shield SprayBefore every use of a hot tool$26.00
1SC-02Scalp Comfort SerumDaily if wanted$30.00
1RT-01The Fine Hair WeekA complete week$84.00
1SR-01Weightless Smoothing SerumDaily, on damp or dry hair$28.00
2CN-02Bond Repair MaskOnce a week$34.00
2SR-02Glass Shine Serum2–4 times a week$30.00
2CN-04Leave-In MilkEvery wash day$26.00
2SR-08Protein Strength SerumOnce or twice a week$32.00
2ST-02Texture SprayAs needed$24.00
2RT-02The Repair WeekA complete week$86.00
3SR-03Squalane Hair Oil2–3 times a week$32.00
3ST-03Styling CreamAs needed$26.00
4CN-03Deep Moisture MaskOnce or twice a week$34.00
4SR-05Frizz Control SerumOn wash day, or as needed$30.00
4RT-03The Curl WeekA complete week$92.00
5SR-06Overnight Repair OilOnce a week, overnight$34.00