Which test is commonly conducted prior to bleaching hair?

The strand test is commonly performed before bleaching hair to assess the hair's reaction to the bleaching process. This test involves taking a small section of hair and applying the bleach to it, allowing the stylist to observe how the hair lifts and lightens in color. The results of this test provide vital information about the hair's condition and how it will respond to the chemical treatment of bleaching.

Conducting a strand test allows the stylist to determine the appropriate processing time needed to achieve the desired level of lightness while minimizing potential damage. It also helps in evaluating the hair's overall health, which can influence the choice of product and technique used to ensure the best results without compromising the integrity of the hair.

While a patch test is also important, as it checks for allergic reactions to the chemicals, it does not provide the same level of information about how the hair itself will respond to the bleach. The porosity and elasticity tests are useful for understanding hair health, but they do not directly assess the effects of the bleaching process on the hair. Therefore, the strand test is the most relevant procedure for ensuring safe and effective bleaching results.