Which process involves applying products to hair for permanent texture change?

The process that involves applying products to hair for a permanent texture change is relaxing. When hair is relaxed, chemicals are used to break down the disulfide bonds within the hair's structure, which alters its natural curl pattern. This process can transform curly or wavy hair into a straighter, smoother texture. The products typically contain strong chemicals that allow for this significant change and the effects are long-lasting.

In contrast, straightening and curling usually refer to temporary styling methods applied with heat or styling tools, which do not permanently alter the hair's internal structure. Waving can also be associated with temporary styling techniques rather than a permanent change in texture. Thus, relaxing is distinct in that it is specifically aimed at achieving a lasting alteration in the hair's texture.