How Do I Switch Professional Colour Lines Safely?
The short answer
Switch lines one client at a time, and only on a formula you can already mix from memory. Convert the level first, then the tone, then strand test before applying the full head. Do not convert a multi-tone corrective formula in one step.
Updated
A safe conversion order
- 1Compare the two shade charts side by side rather than the two names. Names are marketing; numbers are structure.
- 2Match the level first. Levels are the most portable part of the notation.
- 3Match the tone family second, then adjust for the new line strength by testing.
- 4Strand test on the client before the full application, even if the formula is routine.
- 5Log the conversion in the client record so the next appointment does not re-derive it.
What to convert last
Corrective formulas built from three or more shades, and any formula that depends on a specific series base, should be converted last and with a test. Those are the formulas where a small shift in pigment load changes the outcome.
Frequently asked
Do level numbers mean the same thing in every brand?
Broadly yes for major professional lines, which makes level the safest thing to convert. Base series and suffix letters are where brands diverge.
Can I mix developer from two brands?
It works, but it adds an unknown to a corrective service. Use the brand-matched developer, and check it is the same volume.
Keep reading
- Do Different Brands of Developer Work Differently?Same volume, different behaviour — why brand-matched developer removes an unknown.
- How Do I Read a Hair Colour Number?Level, primary tone, secondary tone — and why brand suffix letters change everything.
- What Formula Covers Resistant Grey?Permanent, one level lighter than target, 20 volume, natural series at half — and why grey goes hot.
- Are Bond Builders Worth the Cost?Worth it on real lift, optional on deposit-only colour — and never a substitute for judgment.
Part of Brands & Products in the S2 Academy.