What each volume does
Developer is hydrogen peroxide, and its strength is printed as a volume or as a percentage. Ten volume is three percent, twenty is six percent, thirty is nine percent, and forty is twelve percent. The developer opens the cuticle and activates the dye, and the strength decides how fast the chemistry runs and how much natural pigment can be removed. More volume is not more skill. It is more speed, more lift, and more damage, and every step up the scale narrows the margin for error. Choose the lowest volume that reaches the target, and let the strand test confirm the choice before the formula touches the head.
Ten volume, three percent, is a deposit developer. It has no useful lifting power on natural dark hair, and it is the right choice for gloss, toner, and deposit-only colour. It is also the volume for refreshing faded ends when the target is the same level or darker, and for a semi-permanent or demi-permanent line that the brand formulates for low volume. Ten volume is gentle, which makes it the safest choice on porous or previously lightened hair. It is not a weak version of a lifting developer; it is a different job. Using it to lift is like using a brush to hammer a nail.
Twenty volume, six percent, is the working default for permanent colour. It gives roughly one to two levels of lift, it covers grey when the formula has enough natural base, and it is designed for use on the scalp within the brand's directions. Most global colour and most root retouches are built on twenty volume. It is strong enough to open the cuticle and deposit, and mild enough that a routine service does not leave the scalp raw. When a client asks for a stronger developer to make the colour last longer, explain that twenty volume with enough pigment and full development time lasts longer than forty volume with a weak formula.
Thirty volume, nine percent, gives roughly two to three levels of lift and exposes more warmth, which means more toner work at the end. Use it off the scalp where the manufacturer allows, and use it only when the strand test shows the hair tolerates it. Forty volume, twelve percent, is maximum lift and maximum damage. It is not a routine scalp developer for grey coverage or a root retouch, and it is not a shortcut to blonde on a level two base. On a scalp that has any tenderness, forty volume can produce a chemical burn before the colour has developed. There are salon situations where a brand permits forty volume off the scalp; those situations are technical decisions, not habits.
- 1. 10 volume is 3 percent: deposit and tone only, with no useful lift, for gloss and toner.
- 2. 20 volume is 6 percent: the default for permanent colour, grey coverage, and 1 to 2 levels of lift.
- 3. 30 volume is 9 percent: 2 to 3 levels of lift, more warmth exposed, and off the scalp where possible.
- 4. 40 volume is 12 percent: maximum lift and maximum damage, and never a routine scalp developer.
- 5. Do not use 40 volume for a root retouch or for grey coverage, because the scalp risk is not worth the speed.
- 6. Drop the volume on porous, previously lightened ends and shorten the time instead of adding strength.
- 7. Follow the brand's developer range, because some lines allow only 10 and 20 volume for a given shade.
- 8. Choose the lowest volume that reaches the target, and confirm it on a strand before the service.
Salon example
Ritu has a natural level four base, about twenty percent grey, and wants a level six warm brown. She has coloured at home twice with a box kit and her ends are a level five. The lift needed at the root is two levels, and the ends need deposit, not lift. I mix the root formula at 20 volume with a level six natural base and a level six gold, and the ends with 10 volume at the same shade for the last ten minutes, per the brand. The root covers in thirty-five minutes and the grey at the temples needs the full time. If I had used 40 volume to speed the root, the scalp would have tingled within minutes, the root would have lifted past level six into orange, and the ends would have grabbed the gold and gone darker. The client would have left with hot roots and dark ends, which is the opposite of the soft, even result she asked for. She books her retouch at five weeks, and I write the volumes on her card.
Caution: Forty volume on the scalp is not a shortcut to a lighter result. It raises the risk of a chemical burn and often lifts past the target into unwanted warmth.
Overlap, banding, and the lightened hair rule
Overlap is product applied over hair that has already been processed. Every colour service leaves the cuticle slightly more open than it was, and lightener leaves it significantly more open. When fresh product goes over that hair, the chemistry runs faster and stronger than it did the first time. The result is extra deposit, extra damage, or both. A client who has overlapping root colour every four weeks for two years ends up with mid-lengths that are darker and duller than the root, even though the formula never changed. The overlap, not the formula, is what the client sees in the mirror.
Banding is the visible line that overlap and uneven application leave behind. It usually appears where a retouch stopped short of the previous colour line, or where the product was dragged down the mid-length on the way to the ends. A band can be darker, lighter, or warmer than the hair above and below it, depending on what was applied. The way to avoid it is mechanical: section finely, apply to the new growth only, keep the application inside one to two centimetres of regrowth, and do not pull the brush through the old colour to tidy the line. Tidying with the brush is how a soft line becomes a hard band.
The lightened hair rule is absolute in a well-run salon: do not overlap lightener on hair that has already been lightened. That hair has already lost pigment and cuticle integrity, and a second application compounds the damage and creates a patch or a band. On a retouch, lift only the new growth and treat the previously lightened area as off-limits. If the ends need a tone refresh, use a toner or a gloss, not lightener. If the mid-length needs more lift, that is a new service with its own strand test and its own plan, not a touch-up at the end of a root appointment.
Repairing a band is correction work, and correction is staged. Do not lighten the band on the same day you discover it, especially if the surrounding hair is already porous. Assess the band's level and tone, test a softener or a toner on it, and plan two visits. A root smudge can blur a dark band at the top, and a toner can pull a warm band closer to the surrounding colour. If the band is a hard line from overlapping lightener, the honest answer may be to grow it out and cut it. Say that early, because a client who is promised a one-visit fix will blame the salon when the band is still visible.
- 1. Apply a retouch only to the new growth, within 1 to 2 cm, and never drag the brush through the old colour line.
- 2. Do not overlap lightener on previously lightened hair, because it compounds damage and creates a band.
- 3. Keep 40 volume away from the scalp and away from any hair that has already been lightened.
- 4. Refresh lightened ends with a toner or gloss, not with more lightener.
- 5. Section finely so the product reaches the hair underneath, because a thick section processes unevenly.
- 6. If a band appears, assess it, strand test a softener or toner, and correct across 2 visits.
- 7. Offer a root smudge for a soft grow-out only when the band is dark and near the root, not for a mid-length band.
- 8. Record where the old colour line sits, so the next retouch does not repeat the overlap.
Salon example
Meenal has been colouring her roots at home every month for a year with a level five box shade. She comes in because the mid-lengths look darker than her roots and she thinks the colour is fading. In daylight her root is a level five, and there is a distinct darker band about four centimetres down, then a lighter, warmer level six through the ends. The band is overlap, not a fading problem. Lightening the band is not the first move, because the ends are already porous and a lightener pass would make the band lighter at the top and gummy at the bottom. I propose a plan: today, a level six ash gloss over the mid-length and ends to soften the contrast, and a root retouch that stops short of the band. In four weeks, a second gloss to blend, and a trim to remove the oldest ends. She agrees, and I write the band's position on the card so the next retouch stays above it. The fix takes two visits, and the hair stays intact. She also books a gloss at five weeks, because the ends will need tone before the band grows out, and the gloss costs less than a correction.
Caution: Do not try to fix a band by lightening it on the same day, especially when the surrounding hair is porous. Two visits is the safe plan.
Mixing and timing discipline
Developer starts working the moment it meets the colour. There is no pause button, and a bowl mixed for an earlier client is not the same product twenty minutes later. Mix fresh for each client, in the ratio the brand prints, and use the bowl size that matches the job. A permanent colour is often one to one, some lines are one to one and a half or one to two, and a lightener is often one to one and a half or one to two to a smooth paste. If the brand says one to one and a half, use one to one and a half. The typical ratios in a textbook are a starting point, not a licence to override the tube.
Timing belongs to the manufacturer. A permanent colour is often thirty to forty-five minutes, resistant grey can go to forty-five within the brand's limit, a toner is five to twenty minutes, a gloss is ten to twenty, and a lightener is checked from twenty minutes and then every five to ten. Those ranges are typical, and the tube is the authority. Do not leave a colour on longer because the client is not covered yet; fix the formula or the application instead. Do not rinse a colour early because the salon is busy. A colour that has not developed fully fades in a week and the client blames the product, the water, or the salon.
Application pace matters as much as the clock. On a long, thick head, mix in two batches so the second batch is fresh when the first is already on the hair. Keep foils saturated and closed, because lightener that dries stops working and the hair underneath stays orange. Do not let product sit in a warm window or on a trolley in direct sun. Use the tools the brand specifies, and keep the bowl and brush clean between clients. A contaminated bowl or a dirty brush can change the way the product behaves, and it is the kind of error that never appears in the strand test.
When the service runs long, remix rather than stretch. Adding water to a thick bowl, or topping up an old bowl with fresh developer, changes the ratio and the strength, and the result becomes unpredictable. If you run out mid-head, wipe your gloves, mix a fresh bowl at the correct ratio, and carry on. Note the actual time each section received, not the time you planned. The card should say thirty-five minutes at the root and ten at the ends, because that is what happened. The next colourist, possibly you in six weeks, needs the truth rather than the plan.
- 1. Mix fresh for every client, because developer begins working on contact and a held bowl is already spent.
- 2. Use the brand's ratio: often 1:1 for permanent colour and 1:1.5 or 1:2 for lightener, never a guess.
- 3. Set the timer for the manufacturer's time, typically 30 to 45 minutes for permanent colour and 5 to 20 for toner.
- 4. Check lightener from 20 minutes, then every 5 to 10, and never leave foils unattended.
- 5. Mix a second fresh batch on long or thick hair instead of stretching the first bowl.
- 6. Never add water or leftover developer to a mixed bowl to make it last longer.
- 7. Keep foils saturated and closed, because dried lightener stops lifting and leaves a band.
- 8. Record the actual development time per zone on the card, not the time you intended.
Salon example
Farida has very long, thick, level three hair and wants a global level five chocolate brown with full grey coverage at the temples. The head is too large for one bowl, so I mix two batches: the first for the roots and the resistant temples, the second for the mid-length and ends. I apply the roots first at 20 volume, set the timer for thirty-five minutes as the brand instructs, and mix the second batch ten minutes before I need it. At thirty minutes the temples are covered and the root is a clean level five. I pull the second batch through the mid-length for ten minutes and the ends for five, then rinse. If I had mixed one large bowl at the start, the second half would have been weak by the time it reached the ends, and the result would have been uneven. The card records the two batches, the volumes, and the actual times, so the next visit can repeat the result. She asks whether the second batch could be mixed at the start to save time, and I explain that a bowl mixed early is a bowl that is already working before it reaches the hair.
Caution: Never add water to a thick colour bowl or top it up with fresh developer. Both change the ratio, and the result stops being predictable.
This is a Nandu Nai textbook. It is a private brand book, not a government licence, and it does not give the right to give medical treatment.