In this blog post, we will learn how perming changes the internal bonds of hair through oxidation and reduction reactions to maintain the desired shape for a long time.
How much time do people need to spend on their hair in the morning before leaving for work? The exact amount of time varies from person to person, but rather than styling straight hair with a hair dryer or wax every day, getting a permanent wave, commonly known as a perm, is a quick and easy method. Permanent means “permanent,” and once done, it has the advantage of maintaining its shape even after washing your hair. Unlike temporary styling tools, permanent waves allow you to maintain your desired hairstyle for a long time, making them a very useful choice for busy modern people. Unlike blow-drying, which uses heat to remove moisture from the hair and temporarily maintain its shape, a perm changes the molecular structure of the hair itself through oxidation and reduction. This structural change is not just a simple styling technique, but a fundamental change.
Unless special chemicals are applied, the hair will quickly return to its original state even if it is bent or twisted arbitrarily. This is because the cystine that makes up hair protein is connected to other hair proteins by sulfur-sulfur bonds, forming a ladder-like structure in which neighboring protein molecules are connected by sulfur-sulfur bonds. This structure is an important factor in determining the elasticity of hair and helps it maintain its natural shape. The sulfur-sulfur bonds connecting neighboring proteins are covalent bonds, so they are stronger than other intermolecular bonds that are temporarily formed depending on the shape of the hair. Therefore, sulfur-sulfur bonds can restore bent hair to its original shape, and in order to change the shape of hair, it is important to break the sulfur-sulfur bonds (S-S) of the cystine ladder.
So how can the sulfur-sulfur bonds in the cystine ladder be broken? Sulfur-sulfur bonds are covalent bonds in which each atom gives up one electron, resulting in a total of two electrons shared between the two atoms. Through this bond, each sulfur atom has two electrons, which is equivalent to having one more electron. However, because the same sulfur atoms are bonded together, there is a limitation in that the sulfur atoms cannot hold electrons close enough to each other. In other words, if we think of the atoms in this bond as magnets and the electrons as iron powder, the magnets on both sides of the bond have the same force, so the iron powder will be located in the center of the two magnets and will be farther away from the magnet than when there is no magnet on the opposite side. This characteristic of the bond is one of the reasons why hair is difficult to maintain a specific shape.
Therefore, in order to break the sulfur-sulfur bond, it is necessary to combine the sulfur atom with an atom that has a weaker ability to attract electrons, so that it can attract electrons more easily while producing the same effect as having one more electron than the sulfur atom originally had. If there are such atoms in the vicinity, the sulfur atom breaks the sulfur-sulfur covalent bond, which attracts electrons with equal force, and forms a new covalent bond with atoms that have a weaker force to attract electrons. In this case, the two atoms that form the bond give up one electron each and share two electrons, so the effect of the sulfur atom having one more electron is maintained, while the electrons are located closer to the sulfur atom because it has a stronger attraction to them. The key to this process is to enable the hair to maintain its new shape through the new bonds. The most commonly used bonding agent in this case is hydrogen (H), and the process of an atom bonding with hydrogen is called “reduction.” Therefore, when a reducing agent is applied in the first step of perming, each sulfur atom bonds with a hydrogen atom, breaking the sulfur-sulfur bonds and allowing the hair to change shape.
However, just because the bonds that maintain the shape of the hair have been broken and the shape can be changed does not mean that it will be fixed in the desired shape. The hair that has changed shape is still in an unstable state, and if left in that state, it will tend to return to its original shape. After breaking the sulfur-sulfur bonds in the hair with a reducing agent and curling it into the desired shape using a cylindrical device, it is necessary to fix the hair in that shape. In this process, sulfur loses hydrogen atoms, and this process of removing hydrogen atoms from an atom is called “oxidation.” The components that cause this reaction are oxidizing agents, which are atoms that attract electrons more strongly than sulfur atoms. Therefore, oxidizing agents tend to combine with hydrogen, which has a weak electron-attracting force, in order to attract electrons more easily. As a result, sulfur atoms, which are weaker than oxidizing agents, lose hydrogen and form sulfur-sulfur bonds with neighboring sulfur atoms. Applying heat at this point accelerates the formation of new sulfur-sulfur bonds, so in the case of heat perm, a type of perm, heat is applied after applying the oxidizing agent. When new sulfur-sulfur bonds are formed through this process, these bonds become the force that maintains the shape of the hair, keeping the curled shape intact.
In this way, perming is a treatment method that changes the molecular structure through oxidation and reduction reactions, resulting in a change in the shape of the hair. This is not just a simple cosmetic treatment, but a process based on scientific principles, and its effects can be maintained for a long time. Although it is a very stable and permanent method because it forms new bonds, it cannot be said that the shape will never change because gravity constantly acts on the hair and it is periodically exposed to chemicals such as shampoo and conditioner. In addition, changes in the external environment and hair growth can also affect the permanence of a perm over time. However, considering that temporary hairstyles created using existing heat sources such as hair dryers are washed away by water, permanent waves, which change the molecular structure of the hair, can be said to be a truly “permanent” hairstyling method.
