Final answer:
In cosmetology, when blending gray hair with color, a common rule is to add an equal part of Natural Brown (NB) to the primary color. The exact percentage can vary depending on the product brand and desired result, making it essential to follow the manufacturer's instructions.
Step-by-step explanation:
The question 'What % do NB should be added when blending gray?' relates to the field of cosmetology, specifically regarding hair coloring techniques. The 'NB' stands for Natural Brown, which is a standard color designation in hair dye products. When blending gray hair, professionals typically mix a certain percentage of Natural Brown (NB) with other colors to achieve a more natural, blended outcome. The exact percentage can vary depending on the brand of the product and the desired result, but a common rule of thumb is to add an equal part of the Natural Brown (NB) shade to whatever primary color you are using. For instance, if a client has 50% gray hair and wishes to go to a level 6 (dark blonde), the colorist may mix 50% of a 6N (natural dark blonde) with the desired 6 level shade, ensuring a natural coverage of the gray.