Dying the underside of hair involves separating the top layer of hair from the bottom layer, then applying dye to that portion only. Having a friend or family member help with the process prevents dye from reaching unwanted places, such as the top layer of hair or the skin of the neck and shoulders.
When dying underneath the hair, a standard hair dye works just fine. It should be several shades lighter or darker than the natural hair to ensure a dramatic contrast between the two layers. Experts recommend pairing black hair with platinum blond dye, for example, or brunette hair with pale auburn dye. Additionally, it helps to start with a layered hair style so that the underside shows up against the top layer.
Step 1: Prepare the hair
Before dying, the hair should be combed and completely dry. The amount of hair to leave in its natural color is up to the individual; professionals recommend using the line at the top or bottom of the ear or the parietal ridge, which is the curved area of the skull, as guidance. The hair that is not going to be dyed should be pinned to the top of the head with hair clips so it is out of the way.
Step 2: Dye the underside of the hair
The individual or a helper should dye the underside of the hair according to the manufacturer's instructions. A comb or brush can help distribute the dye evenly without contaminating the pinned top layer. The individual should wash the hair afterward, blow it dry and blend it with the top layer to view the finished result.