What does the term "foiling" refer to in hair coloring?

The term "foiling" specifically refers to the technique of using foil to separate sections of hair for highlights. This method involves placing strands of hair between sheets of aluminum foil while applying a lightening product or color. The foil serves multiple purposes: it helps to keep heat close to the hair for more effective processing, prevents the color from bleeding onto surrounding hair, and allows the stylist to focus on specific sections for a more controlled highlighting effect.

This technique is particularly popular because it can produce very precise and well-defined highlights, as well as allow for different colors or lightening processes to be applied without interference from other sections. The use of foil is essential for achieving a clean and segmented result, which is why this technique is distinct from others that might involve different applications or methods of presenting color.