Is a strand test necessary and how should it be done?

A strand test is recommended, especially on light, bleached, porous or chemically processed hair, because the final shade and intensity can differ from the expected colour.

To perform the test, take a small section of hair that has not been previously coloured, apply the prepared henna paste, cover it, and leave it for the same 2–4 hour period used for a full application. Rinse and evaluate the colour; if the result is too light, increase the exposure time or add a little more powder, and if it is too dark, reduce the time or dilute the mixture before the full treatment.

It is also advisable to avoid using the product if the scalp is irritated or if there are any open wounds, and to remember that plant colour can be stubborn to remove or recolour within 24‑48 hours, so the test helps prevent an unsatisfactory overall result.