Every brand has a plex now, there's at least one bottle on the back bar promising to rebuild or repair, and every rep turns up with a chart of before and afters. Some of it does real, measurable work inside the hair, and some of it is conditioner with a clever name and a premium price. Knowing which is which saves you money on the trolley and stops you overpromising at the chair.

What a bond builder does

Hair holds its strength through bonds inside the shaft, and the ones that matter most for chemical work are the disulphide bonds. Lightening and other chemical processes break them, and broken disulphide bonds are why bleached hair stretches, snaps and goes to mush when it's wet.

A genuine bond builder carries an active ingredient that reaches into the shaft and reforms or mimics those broken disulphide links. That's a real chemical reaction rather than a surface coating, which is why adding one to your lightener lets you push a lift the hair couldn't otherwise survive. Olaplex built its reputation on that reaction.

Reducing damage and rebuilding internal structure is as far as bond builders go. They won't make damaged hair new, and split ends are mechanical damage that only scissors fix.

Bonds versus moisture

The confusion on most shelves is that "repair" gets used for two completely different jobs. Bond building rebuilds internal structure and gives you back strength. Moisture and protein treatments work more on the surface and the cortex, improving how the hair feels, looks and behaves day to day.

Both are useful, but they fix different problems. Hair that snaps when wet and feels like chewing gum has a bond problem, and no amount of rich conditioning mask will hold that hair together. Hair that's structurally sound but dry, dull and rough wants moisture, and throwing an expensive bond treatment at it does very little because the bonds were never the issue.

Diagnose which one you're looking at before you pick a treatment. Wet-stretch the hair: if it stretches a long way and doesn't spring back, or snaps, that's bonds, and if it feels brittle and parched but holds, that's moisture. Treat the wrong fault and you've wasted the product and a treatment slot on a problem the client still has.

How to check a bond claim

The category got hot, so everything got "plex" on the label, and a lot of those bottles are decent conditioners trading on a word. Check three things before you buy:

  • Where it sits in the range. A serious bond builder is designed to go into the lightener and through the colour process. A product that's only ever sold as a rinse-out mask at the backwash is a conditioning treatment, whatever the name suggests.
  • What it promises. "Repairs three years of damage in one wash" is marketing. Reforming bonds and reducing breakage during chemical services is a claim a reputable manufacturer will stand behind.
  • What the home version is. Plenty of retail "bond" ranges are gentle, pleasant maintenance products. They're fine to sell, as long as you're honest that they protect and prolong rather than rebuild.

When to add a bond builder

A bond builder pays for itself when it lets you take on work you'd otherwise turn away or do in more sessions: the box-dye blonde, the lift on compromised hair, the client who wants to go several levels and keep her length.

A bond builder is wasted when you add it to everything by reflex on a root tint that was never going to damage the hair, or when you sell a pricey in-salon bond treatment to someone whose problem was always dryness. Charge for it where it does the work and leave it off where it doesn't, and clients learn to trust what you put on their bill.