Which of the following helps in evaluating the porosity of hair?

Performing a strand test is essential in evaluating the porosity of hair because it allows you to assess how well the hair absorbs and retains moisture and products. During a strand test, a small section of hair is saturated with water and observed to see how quickly it absorbs the moisture. Hair that absorbs water quickly is considered to have high porosity, while hair that takes longer to absorb water has low porosity. This test provides immediate insights into the hair’s condition and its ability to hold chemical treatments, which is crucial for making informed decisions about chemical services like coloring or texturizing.

Other options do not directly assess porosity. Using a heat tool primarily assesses the hair's ability to withstand heat without damage rather than its moisture absorption capabilities. Applying deep conditioner can improve the condition of the hair but does not provide a direct evaluation of porosity. Examining hair color may give some clues about the hair's condition, but it doesn't specifically measure its porosity. Therefore, performing a strand test is the most accurate method for evaluating hair porosity.