In daily life, hair is regarded as an ornament. Throughout history, people have been looking for ways to curl their hair. Perm is closely related to the development of perm tools. It can be said that the promotion of perm tools leads the development of perm.

Perm is actually divided into physical perm and chemical perm:

Chemical ironing

Cold perm (chemical perm) only appeared in the 1930s. Reducing agents used in cold perm are mercaptoacetate and esters, which destroy hydrogen, salt, ammonia and disulfide bonds in hair, thus achieving the effect of perm. Therefore, cold perm is the most harmful perm method for hair, and people generally do not advocate such a perm method.

Physical ironing

The earliest method of physical perm is to wrap the hair around a round stick, dry it in the sun to become curly hair, then heat it in advance with tools such as electric tongs or iron bars, and then roll it into waves. This method is very harmful to hair quality and has been abandoned with the development of science and technology. In the 1990s, ceramic ironing was invented in South Korea, and then spread to Japan, then to Taiwan Province Province, and finally to China. This is a long process, and ceramic ironing has been popular until the beginning of the 20th century. In August 2002, people began to popularize digital perm in SPA. This technology was invented by China Meiyu Company and independently developed by China Zhengzhen in the hairdressing industry. It breaks the traditional western perm method, and uses safe voltage with an output of 24V less than 36V to supply power to people's heads, which greatly guarantees people's safety in the perm process. Until now, no perm technology is more advanced, healthier and safer than digital perm.