Before the popularity of boxed drugstore hair colour, salon hairstylists applied a hair colouring method called the foil technique. The foil technique creates one or multiple coloured highlights in your hair. Better placement of colour is one benefit of foil highlighting over drugstore highlights. Generally, stylists have a choice from three techniques for the foil method: slicing, weaving or panelling.
Slicing is one of the faster methods for highlighting and probably the most used technique for salon professionals. In order to slice, a stylist sections the hair 3 inches wide, and from 1/6 to 1/8 inch thick. Keep the strands thin. Place a square piece of foil approximately 4 inches wide underneath a single strand. Liberally brush the colour onto the strand and fold the foil over and secure. A stylist will apply the slicing process either horizontally, vertically or diagonal, depending on how you would like the highlighted piece to lay.
Weaving is a technique that, when combined with slicing, creates more natural highlights. To do the weaving method, begin by parting the hair into very small sections---no more than 3 inches wide and 1/8 inch thick. With the tail end of the comb, begin at the surface and move in a zigzag pattern until you have separated the row. Place a 3 to 5 inch square piece of foil underneath the strand of hair. Brush the colour onto the entire strand and then fold the piece of foil and secure. A second option to the weaving technique is to complete the process as described above, but instead of using only small sections, part the hair into small, medium and larger strands. This gives more highlight variety.
This technique is also known as colour blocking. It may be a little trickier than the others so you may want to utilise a professional stylist. Panelling, or blocking, is a drastic technique, intended for an edgier look, which leaves large portions of the hair a contrasting colour from the rest. To use the panelling method, separate sections of hair you want coloured with hair clips. Lay the chunk of hair underneath a square piece of foil large enough to cover the chunk. Apply the colour, fold the foil in half and secure.
When finished with the technique of choice, simply remove foil and thoroughly wash out colour. Use a conditioner to combat dryness and for extra softness. Dry the hair and style as desired.