Color History Questions That Change Your Formula

Why does color history change the formula?

Because you are never colouring hair — you are colouring hair plus everything that has already been done to it. Two clients with an identical natural level and identical target can need entirely different formulas, different developers and, in some cases, a refusal to proceed.

History changes three things at once: what pigment is physically present in the shaft, how porous that shaft is, and whether there is anything in it that will react with peroxide. The first two change your formula. The third changes whether there is a service at all.

The nine questions and what each one changes

Ask all nine, every time, and record the answers. The right-hand column is the answer that should stop you and change the plan.

How do you detect box dye when the client says no?

Clients under-report box dye, usually without meaning to — home colour six months ago genuinely does not register as "colouring your hair" to someone who is not a colorist. Read the hair instead of the answer.

• A hard line of demarcation. Professional regrowth fades at the boundary; box dye tends to stop abruptly.
• Ends darker than the mid-lengths. Repeated full-head home application builds deposit on the oldest hair. Salon application runs the other way.
• Banding at intervals. Distinct horizontal bands roughly matching a re-colouring cycle.
• An unnaturally flat, opaque tone. Box formulas carry high dye loads for guaranteed coverage, and the result reads without depth variation.
• Resistance to lift in patches. The most practical tell — and the reason to strand test rather than argue about the history.

When the hair says box dye and the client says no, believe the hair, strand test, and set expectations before you start rather than mid-service.

The strand test for suspected henna

Compound henna and some traditional dyes contain metallic salts. Metallic salts react with peroxide exothermically — they can heat, smoke, turn the hair green, and in a bad case melt it off. This is the one test on this page that is not about the result being disappointing.

Three outcomes:

1. Nothing happens. No metallic salts detected. Proceed with normal caution and a standard strand test.
2. The hair lightens rapidly, or the solution heats, bubbles or smells. Metallic salts present. Do not apply peroxide to this head.
3. The hair turns green, or feels gummy and pulls apart. Metallic salts present, and the hair is already compromised. Same answer, more emphatically.

A negative result is not a guarantee across a whole head that may have been treated unevenly. If the history says henna and the test says nothing, treat the history as the stronger signal.

What does porosity tell you that history doesn't?

History tells you what was done. Porosity tells you what the hair became — and it is the variable that decides how fast your formula will take and how long it will hold.

• Low porosity: product sits on the surface, colour takes slowly, resists. Often the same hair that needs pre-softening for gray coverage.
• Normal: takes and holds predictably. Formulate to the chart.
• High porosity: grabs fast, goes darker and cooler than intended, releases quickly. Reduce deposit, shorten the timer, consider filling first.

Porosity is usually uneven along a single strand — low at the root, high at the ends. That gradient is why the same formula produces three different results down the length, and it is what zonal application exists to solve.

Patch testing and what the record must show

Oxidative colour contains PPD or PTD, and sensitisation can develop at any point — including in a client who has been coloured for twenty years without incident. A previous uneventful service is not evidence of current tolerance.

Requirements vary by country, and in some places by insurer. Timing before the service, what has to be recorded, and whether a documented refusal is acceptable at all are all jurisdiction-specific. This article does not tell you what your local rule is — check your manufacturer's instructions and your own insurance terms, because those two are what you will be held to.

What the record should carry regardless of jurisdiction:

• Date and time the test was performed, and by whom.
• The exact product tested, not just the brand.
• The result, and when it was read.
• If the client declined: that they were told why it matters, and that they declined — in their words, dated.

What to record after the service

The consultation is only half the value. What makes the next appointment faster is a record of what you actually did and what it actually did.

1. The formula as mixed — shades, quantities in grams, developer volume, ratio.
2. Timing and sequence — where you started, what went on when.
3. Result against target — and if it missed, in which direction. "Half a level light, needed 40 not 35 minutes" is worth more next visit than a photograph.
4. Anything the hair did that surprised you — the ends grabbed, the hairline resisted, the ash went flat.
5. Standing flags — prior henna, a previous reaction, a recent relaxer. These must survive to the next visit, because they are the ones that stop being remembered.