What does a strand test help determine?

A strand test is a crucial procedure used in cosmetology to assess how a particular chemical process, such as perming or hair lightening, will affect the hair. By taking a small section of hair and applying the chemical solution to it, the stylist can observe how the hair reacts to the product. This allows for the determination of processing time needed for the desired outcome, helping to avoid damage and ensuring consistent results across the entire head of hair.

In the context of the other options, while hair density refers to the number of hair strands on the scalp, and hair texture describes the thickness or coarseness of individual strands, these factors do not provide information about how a chemical process will impact the hair during treatments. Similarly, color matching is primarily focused on selecting the right shade to achieve the desired color result, which is distinct from understanding how a chemical application will process the hair. Therefore, the primary purpose of a strand test is to gauge processing time, making it essential for achieving optimal results in perming or lightening hair.