When a person uses a hair color product to change the color of her hair, hair root touch up usually becomes necessary about once every four to six weeks. This is because hair grows at the rate of about one-half inch (1.27 cm) per month. This new growth creates a distinctive line where the hair color was last applied and the natural color has grown in. This area of growth at the roots can be touched up using either liquid hair color or cream hair color. Hair root touch up methods may also vary according to whether the hair color is darker or lighter than the person's natural color.
Liquid hair color has a fairly thin consistency. It is usually mixed with a developer, such as hydrogen peroxide. When touching up the root area, liquid color is typically mixed and squeezed onto the hair through the small nozzle of a plastic bottle. The color is rubbed onto the root area where the new growth appears and left on, or processed, until the desired color is achieved. If the previously color of hair has faded, it may also be pulled through to the ends to add depth.
Cream hair color comes in small tubes, similar to travel-size toothpaste. It is squeezed out of the tube into a small bowl and mixed with the appropriate developer using a thin brush. The same brush is used to apply the color for the hair root touch up. Like liquid color, cream color must be left on the hair for the recommended amount of time, and may also be pulled through to the ends if necessary.
When doing a hair root touch up to lighten the natural color of the hair, if there is more than one inch (2.54 cm) of re-growth, the color may not be applied directly on the scalp initially. This is because the scalp area is warmer and will lighten faster than the rest of the hair shaft, resulting in uneven color. After applying the color to the area about one half inch (1.27 cm) away from the scalp, it should be processed until it is about halfway to the desired color. The product can then be applied directly to the scalp area and processed until the root area matches the rest of the previously colored hair.
If the desired color is the same shade or darker than the natural hair color, the product can be applied directly on the scalp, even if there is more than one inch (2.54 cm) of new growth. The warmth of the scalp area does not usually affect hair color when going darker. The hair root touch up is typically processed until the root area matches the rest of the hair. If the shaft and ends of the hair have faded or need brightening, the color may be applied there the last few minutes before it is rinsed off.