What must be done to a client's hair before lightening?

Testing a client's hair for porosity and elasticity is an essential step before lightening. Understanding porosity helps determine how well the hair can absorb moisture and color. Hair that is highly porous may absorb the lightening product more quickly, leading to potential damage if not monitored closely. Elasticity, on the other hand, assesses the hair's strength and ability to return to its original shape after stretching.

By evaluating both porosity and elasticity, a cosmetologist can make informed decisions regarding the appropriate lightening technique, how long to leave the product on, and whether additional conditioning or protective measures are needed. This step ensures the health of the hair is maintained during the lightening process, reducing the risk of breakage and achieving the desired lift effectively.

Using a deep conditioner or shampooing the hair, while beneficial practices in their own right, do not provide the necessary diagnostic information about the hair's condition and behavior during coloring processes. Similarly, cutting the ends might be necessary for general hair health, but it does not directly inform decisions specific to lightening the hair.