Hair Care After Bleaching — How to Repair Damaged Bonds?

What bleach does to your hair — the chemistry of the process

Bleaching (decolourisation) is one of the most invasive chemical processes we ever put our hair through. A mixture of hydrogen peroxide (H₂O₂, usually 6–12%) and an alkaline bleaching powder raises the hair's pH to 9–11, causing the cuticle to open dramatically. The peroxide penetrates into the cortex and oxidises melanin — the hair's natural pigment.

But melanin isn't the only casualty. Bleach breaks the disulfide bonds (S–S) — the bridges that link keratin chains. These bonds are responsible for the hair's strength, elasticity and shape. It's estimated that aggressive decolourisation destroys 15–45% of disulfide bonds — and this damage is irreversible. Hair cannot rebuild these bonds on its own.

On top of that, bleaching reduces the level of 18-methyleicosanoic acid (18-MEA) — a lipid that forms a hydrophobic protective layer on the cuticle surface. Losing it makes bleached hair hydrophilic (it absorbs excess moisture from the air) and strips away its natural shine.

Bond rebuilding — Olaplex-type technology

The breakthrough in post-bleaching care was bond-repair technology based on Bis-Aminopropyl Diglycol Dimaleate (the active ingredient in Olaplex). This molecule has two active ends that link to the free thiol groups (-SH) — the remnants of broken disulfide bonds — forming new, stable bridges.

This isn't a restoration of the original S–S bonds, but rather the creation of substitute covalent bonds that bring back some of the hair's mechanical strength. Studies published in the Journal of Cosmetic Science showed that using Bis-Aminopropyl Diglycol Dimaleate during bleaching reduces damage by roughly 40–50% compared with bleaching without protection.

Several bond-repair systems are available on the market:

• Olaplex — the original patent, Bis-Aminopropyl Diglycol Dimaleate
• Smartbond (L'Oréal) — maleic acid + castor oil
• Fibreplex (Schwarzkopf) — modified maleic acid
• K18 Peptide — a biomimetic peptide that mimics natural keratin (a different approach from maleic acid)

These products aren't interchangeable — each works on a slightly different principle. What they have in common, though, is that they work most effectively during the bleaching process (added to the mixture) or immediately afterwards. Applying them weeks later has a smaller effect, although it's still beneficial. Compare these ingredients in the PurScore ingredient database.

pH damage — why acidic products are essential

The natural pH of healthy hair is 3.67, and that of the scalp is 5.5. Bleach raises the hair's pH to 9–11. After rinsing, the pH doesn't return to normal immediately — it can stay at 6–8 for several washes, which means the cuticles remain open.

That's why it's crucial to use low-pH products after decolourisation:

• Shampoos and conditioners with a pH of 4.0–5.0 — these close the cuticle
• An acidic apple cider vinegar rinse (1:4 with water, pH ~3.5) — for quick pH restoration
• Masks with citric or lactic acid — for additional cuticle sealing

Manufacturers rarely list the pH on the label, but you can measure it yourself with litmus paper (cost: around 10 PLN for 100 strips). A suitable shampoo for bleached hair should have a pH below 5.5.

Protein–moisture balance — the foundation of care

After bleaching, hair needs both protein (to rebuild structure) and moisture (to replace lost water and lipids). The catch is that too much of either element makes the hair's condition worse:

• Too much protein, too little moisture — hair becomes hard, dry, brittle and "straw-like"
• Too much moisture, too little protein — hair becomes gummy, overly elastic, shapeless and mushy

The optimal approach is to alternate between protein and moisturising masks:

1. Week 1: protein mask (hydrolysed keratin, silk proteins)
2. Week 2: moisturising mask (glycerin, shea butter, panthenol)
3. Week 3: protein mask
4. Week 4: moisturising mask

Watch how your hair responds and adjust the ratio — if your hair feels stiff after a protein mask, space out the protein sessions further.

Avoiding heat — at least 4–6 weeks

After bleaching, hair loses part of its natural thermal protection (18-MEA, cuticle lipids). Heat styling in this state is especially damaging. Recommendations:

• 4–6 weeks with no flat iron, curling iron or hot blow-drying
• After that period: always use a heat protectant (silicones that form a barrier — dimethiconol, cyclomethicone) before any contact with heat
• Flat iron temperature: max. 160°C (instead of the usual 200–230°C). Research shows that keratin starts to degrade above 150°C, and bleached hair has a lower threshold
• Drying: cool air or natural drying. If you must use a blow-dryer, keep it at least 15 cm away and keep the airflow moving

Daily protective habits

• Satin pillowcase — cotton absorbs moisture and creates friction that lifts the cuticle. Satin (or silk) reduces friction by around 50%
• Detangling wet hair — use a wide-tooth comb, starting from the ends. After decolourisation, wet hair is exceptionally prone to stretching and breaking
• Trimming the ends every 6–8 weeks — damaged ends "travel" upwards, splitting the hair higher and higher
• UV protection — bleached hair is more vulnerable to photodegradation. Use products with UV filters (ethylhexyl methoxycinnamate) or wear a head covering

Wondering whether your conditioner contains repairing ingredients? Check its formula in the PurScore.pl search engine — we'll analyse every INCI ingredient for you.