1. The chemical processes of cold perm and hot perm will make hair lose a lot of moisture and protein (especially moisture), and hair without moisture will lack elasticity, toughness and tension. This is why cold perm hair needs moisturizing more to better show the curling effect. But perming is to change the internal and external structure of hair and make it last longer. Therefore, perm curl can be well maintained in dry hair and wet hair.

2. A big difference between cold perm and hot perm lies in the operation procedure. Perm needs to curl the hair with a heated curling iron. This process can be used as a popular example: an iron bar may be deformed by external force, but the deformation effect is difficult. However, the physical shape of this iron bar can be changed to a greater extent by first heating (equivalent to softening hair and heating the winding rod) and then through the mold (equivalent to the shape of the winding rod). Different physical shapes will bring different shapes to hair. Different shapes of hair have different shapes in cross section. The cross section of straight hair is round, the curly hair is slightly flat and oval, and the curly hair is narrow and flat. That is, the difference between cold perm and hot perm is that hot perm can not only change the arrangement of disulfide strings in hair, but also change the physical form of hair more than cold perm. Every hair stylist also knows that the electric wand does not need any medicine, and only the heated electric wand can temporarily curl the hair, but the softened hair without medicine will soon recover its activity. Perm can do both, changing the cross-sectional shape of hair, which is why perm can better keep curly. Straightening itself should belong to the category of ironing, and its function is very similar to ironing.

3. The main components of the liquid medicine (softener and styling agent) used in cold perm and perm are basically the same, and the principles of these two perm methods are basically the same. Are the disulfide bonds (hydrogen bonds and salt bonds) in the hair "cut off" by softener? Softening, and then recombining the cut disulfide bonds with sizing agent. Liquid medicine scalding often adds some anti-heat agents and hair nutritional supplements. Why do you need these drugs for a perm? It is because the perm itself is more harmful to the hair, and the perm is more harmful to the hair. However, the existence of these potions (such as antipyretics) does not affect the homology of cold perm and hot perm principles. This is why some people say that cold ironing liquid can also be used for ironing operation.