Strand Test

Hair strand test
Photo: Depositphotos
Q: What is a strand test and can you tell me how to do a strand test?
A: A strand test is a preliminary test of the hair to determine its suitability for a given process and to verify specifics such as processing times and possible results. It's very important in situations where the hair is damaged, or the intention is to attempt a dramatic alteration to the color of the hair.
Strand tests are used in color processes to ensure that the hair will respond properly to the processes planned, and that said processes won't result in irreparable damage to the hair. It's also important when the stylist cannot be certain what other colors or chemicals have been used on the hair in the past.
For instance, hair that is colored using a metallic salt dye, such as those that offer "gradual coverage" of gray hair, will react horribly if exposed to the peroxide in the developer of traditional hair color. Often the result in these cases is that the hair melts completely.
Strand tests are used for similar reasons with perm services and can also help to ensure that the hair will respond well to a perm service. In the case of perms, the term used is "test curl" but the purpose and result is the same.
Basically, strand testing is a means by which to make sure that the hair will respond appropriately to the chemical service in question without risking the whole head and therefore seriously damaging the hair when it could be prevented.
See also:
How to perform a patch test
Hair porosity test
How to measure hair elasticity