In which of the following areas would you start a retouch application?

Starting a retouch application in the area that is most resistant is important due to the nature of hair growth and the difference in porosity often found in various sections of hair. The most resistant area typically refers to parts of the hair that have had less exposure to chemical treatments, like color or bleach, making them harder to process. This characteristic means that they may not absorb color as readily as other areas.

By applying the retouch formula to the most resistant area first, you allow the product enough time to process to get an even result. This strategy ensures that the more porous areas—which may take on color faster—are treated later, allowing for a more uniform application throughout the entire head of hair. This technique is particularly significant for achieving consistent color from root to tip, especially with permanent color applications, where it's crucial to match the new growth with the previously colored hair.

Choosing a different area, such as those with less damage or with highlights, may not achieve the desired balance in color consistency, leading to uneven results. Understanding hair properties and how they react to chemical processes is essential, and this choice reflects a savvy approach to achieving optimal results in color applications.