- A developer is an oxidizing agent. When mixed with lightener or hair color, it supplies oxygen gas to develop the color molecules, or create a catalyst to begin the lightening process. Hydrogen peroxide is the most commonly used developer and is available in four different strengths. The strengths of developer are called volumes. Choosing the correct volume of developer depends largely on the desired results, natural hair color and hair condition prior to foiling.
- Ten volume is used when less lightening is desired and is the proper volume developer for creating low lights. Twenty volume developer is the standard developer, used to cover gray hair and lighten hair at the roots. Thirty volume is used for additional lift, and forty volume will provide maximum lift for foil highlights. The general rule of thumb is; twenty volume will lift the hair two shades lighter, thirty volume will lift the hair three shades lighter, and forty volume will lift the hair four or more shades lighter.
- Lighteners lighten hair by decolorizing natural hair pigment. When developer is mixed into lightener, it begins to release oxygen. Lighteners are used to create light blond shades that are not achievable with permanent hair color. Hair lightener for foiling is available in cream, oil and powder. There are two primary types of lightener; on the scalp and off the scalp.
- On the scalp lighteners are usually cream or oil. They are easy to apply and appropriate when lightening the hair two to three shades lighter. Most on the scalp lighteners have conditioning agents that protect the hair and scalp. They also contain thickeners to give more control during application. Cream lighteners work well in foils because they do not drip and run.
- Off the scalp lighteners are strong and fast acting. They come in powdered form and are stronger than cream lighteners. Off the scalp lighteners are ideal for high lift blonding but can cause scalp irritation. They should not be applied directly to the scalp.
- The darker the natural hair color, the longer it takes to lighten. Time needed to highlight natural hair color is influenced by porosity. Porous hair will lighten faster and can become broken and frayed. Tone is an important factor when foil highlighting. The more red in the natural color, the more difficult it is to achieve shades of pale blond. Foil highlighting should be performed by a licensed professional. If using lighteners and developers, avoid contact with the eyes and always wear gloves.
