Applied Analytical Systems



  • Chemical hair texture services allow stylists the opportunity to offer clients options to change the texture of their hair and explore the fashionable world of hairstyling.
  • Knowing how to perform these services accurately, safely, and professionally will help build a trusting and loyal clientele while aiding in building your confidence to offer chemical texture services to all clients.
  • Chemical services are among the most lucrative and repetitive services in the salon, and many retail products are specific to hair’s texture and condition.
  • Without a thorough understanding of chemistry, cosmetologists could damage hair, cause hair loss, and harm their clients and themselves.


Chemical texture services are hair services that cause a chemical change that alters the natural wave pattern of the hair.

  • Permanent waving: Adding wave or curl to the hair.
  • Relaxing: Removing curl or waves; leaving the hair smooth and straight.
  • Curl re-forming (self-curl permanents): Loosening overly curly hair; changing tightly curly or coiled hair into loose curls or waves.


All chemical texture procedures involve chemically and physically changing the structure of the hair, we begin by reviewing the structure and purpose of each layer of the hair.

Cuticle: tough exterior layer of the hair. It surrounds the inner layers and protects the hair from damage. Although the cuticle is not directly involved in the texture or movement of the hair, texture chemicals must penetrate through the cuticle to their target in the cortex in order to be effective.

Cortex: middle layer of the hair, located directly beneath the cuticle layer. The cortex is responsible for the incredible strength and elasticity of human hair. Breaking the side bonds of the cortex makes it possible to change the natural wave pattern of the hair.

Medulla: innermost layer of the hair, often called the pith or core of the hair. The medulla does not play a role in chemical texture services and may be missing in fine hair.


  • pH is an abbreviation for potential hydrogen. The symbol pH represents the quantity of hydrogen ions.
  • The pH scale measures the acidity and alkalinity of a substance by measuring the quantity of hydrogen ions it contains.
  • The pH scale has a range from 0 to 14.
    • pH of 7 is neutral
    • pH below 7 is acidic
    • pH above 7 is alkaline.
  • The natural pH of hair is between 4.5 and 5.5. Chemical solutions raise the pH of the hair to an alkaline state.
  • This action opens the cuticle layer of the hair and allows the solution to reach the cortex layer, where restructuring occurs.
  • Coarse, resistant hair with a strong, compact cuticle layer requires a highly alkaline chemical solution.
  • Porous, damaged, or chemically treated hair requires a less alkaline solution.


  • Amino acids: Compounds made up of carbon, oxygen, hydrogen, nitrogen and sulfur.

  • Peptide bonds: Also known as end bonds, are chemical bonds that join amino acids together, end-to-end in long chains, to form a polypeptide chain.
  • Polypeptide chains: Long chains of amino acids joined together by peptide bonds.
  • Keratin proteins: Long, coiled polypeptide chains.
  • Side bonds: Disulfide, salt, and hydrogen bonds cross-link polypeptide chains together.


Keratin proteins are made of long chains of amino acids linked together end-to-end like beads. The amino acid chains are linked together by peptide bonds (end bonds). These chains of amino acids linked by peptide bonds are called polypeptides. Keratin proteins are made of long, coiled, polypeptide chains, which in turn are comprised of amino acids.


  • The cortex is made up of millions of polypeptide chains cross-linked by three types of side bonds.

Disulfide bonds are strong chemical side bonds formed when the sulfur atoms in two adjacent protein chains are joined together. Although there are far fewer disulfide bonds than hydrogen or salt bonds, they are the strongest of the three side bonds, accounting for about one-third of the hair’s overall strength

Salt bonds: Are relatively weak physical side bonds that are the result of an attraction between negative and positive electrical charges (ionic bonds); they are easily broken by changes in pH, and they re-form when the pH returns to normal levels. Salt bonds are broken by changes in pH levels. Even though salt bonds are far weaker than disulfide bonds, the hair has so many salt bonds that they account for about one-third of the hair’s total strength.

Hydrogen bonds: Are weak physical side bonds that are also the result of an attraction between opposite electrical charges; they are easily broken by water (wet setting) or heat (thermal styling), and they re-form as the hair dries or cools. Although individual hydrogen bonds are very weak, there are so many of them that they, too, account for about one-third of the hair’s total strength.


  • Permanent waving is a two-step process whereby the hair undergoes a physical change caused by wrapping the hair on perm rods; the hair then undergoes a chemical change caused by the application of permanent waving solution and neutralizer.
  • When performing a permanent waving service, the size of the rod determines the size of the curl.
  • The shape and type of curl are determined by the shape and type of rod and the wrapping method used.
  • Selecting the correct perm rod and wrapping method is crucial to creating a successful permanent wave. Perm rods come in a wide variety of sizes and shapes that can be combined with different wrapping methods.


  • Alkaline solutions soften and swell the hair and open the cuticle.
  • See the figure illustrating hair saturated in an alkaline solution for five minutes showing the swelling of the cuticle layer.
  • Conversely, see the second figure to see hair saturated in an acid-balanced solution for five minutes. Note there is far less swelling.


  • Once in the cortex, the waving solution breaks the disulfide bonds through a chemical reaction called reduction.
  • A reduction reaction involves either the addition of hydrogen or the removal of oxygen.
  • The reduction reaction in permanent waving is due to the addition of hydrogen.
  • Thioglycolic acid is a colorless liquid with a strong, unpleasant odor, is the most common reducing agent in permanent wave solutions. The strength of the permanent waving solution is determined primarily by the concentration of thio. Stronger perms have a higher concentration of thio, which means that more disulfide bonds are broken compared to weaker perms.
  • The addition of ammonia to thioglycolic acid produces a new chemical named ammonium thioglycolate, which is alkaline and is the active ingredient or reducing agent in alkaline permanents.
  • Degree of alkalinity
  • Coarse hair with a strong, resistant cuticle layer needs the additional swelling and penetration that is provided by a stronger and more highly alkaline waving solution.
  • By contrast, porous hair, or hair with a damaged cuticle layer, is easily penetrated and could be damaged by a highly alkaline permanent waving solution. The alkalinity of the perm solution should correspond to the resistance, strength, and porosity of the cuticle layer.


  • The process of stopping the action of a solution and hardening the hair in its new form.
  • Deactivates waving solution should any be left in the hair.
  • Rebuilds the disulfide bonds into their new shape.
  • Neutralizers are oxidizers; the most common neutralizer is hydrogen peroxide— concentrations vary between 5 volume (1.5%) and 10 volume (3%).


  • Chemical hair relaxing is a process that rearranges the structure of curly hair into a straighter or smoother form. Whereas permanent waving curls straight hair, chemical hair relaxing straightens curly hair.

Other than their objectives being quite different, the permanent wave and relaxer services are very similar. In fact, the chemistry of relaxers and permanent waving is exactly the same. both services change the shape of the hair by breaking disulfide bonds


The most common types of chemical hair relaxers are:

  • Ammonium thio
  • Guanidine hydroxide
  • Sodium hydroxide
  • It should be noted that thio and guanidine are usually classified as no-lye relaxers and sodium hydroxide is considered to be a lye-based relaxer.


  • There are varying degrees and types of curly hair.
  • Extremely curly hair grows in long, twisted spirals or coils. Cross-sections are highly elliptical and vary in shape and thickness along their lengths. Compared to straight or wavy hair, which tends to possess a fairly regular and uniform diameter along a single strand, extremely curly hair is irregular, exhibiting varying diameters along a single strand.
  • The thinnest and weakest sections of the hair strands are located at the twists. These sections are also bent at an extremely sharp angle and will be stretched the most during relaxing.
  • Hair breaks at its weakest point. Extremely curly hair usually breaks at the twists because of the inherent weakness in that section and because of the extra physical force that is required to straighten it.


  • Use the same ATG that is used in permanent waving but at a higher concentration and a higher pH.
  • Usually have a pH above 10.
  • Usually have a higher concentration of ammonium thioglycolate than used in permanent waving.
  • Thicker, with a higher viscosity. Viscosity measures the thickness of a product and affects how the fluid flows. This is more suitable for application as a relaxer.
  • Break disulfide bonds and soften hair. After enough bonds are broken, hair is straightened into new shape and the relaxer is rinsed from hair.


  • The neutralizer used with thio relaxers is an oxidizing agent, usually hydrogen peroxide, just as in permanents.
  • The oxidation reaction caused by the neutralizer rebuilds the disulfide bonds that were broken by the thio relaxer.


  • The hydroxide ion is the active ingredient in all hydroxide relaxers, which are very strong alkalis with a pH over 13.0 Sodium hydroxide, potassium hydroxide, lithium hydroxide, and guanidine hydroxide are all types of hydroxide relaxers, which can swell the hair up to twice its normal diameter.
  • Hydroxide relaxers are not compatible with thio relaxers, permanent waving, or soft-curl perms because they use a different chemistry. The high pH of a thio relaxer is needed to swell the hair, but it is the thio that breaks the disulfide bonds.
  • Hydroxide relaxers have a pH so high that the alkalinity alone breaks the disulfide bonds. The average pH of the hair is 5.0, and many hydroxide relaxers have a pH over 13.0. Since each step in the pH scale represents a tenfold change in concentration, a pH of 13.0 is 100 million times more alkaline than a pH of 5.0.
  • Hydroxide relaxers break disulfide bonds differently than in the reduction reaction of thio relaxers. In lanthionization, the relaxers remove a sulfur atom from a disulfide bond and convert it into a lanthionine bond. A disulfide bond consists of two bonded sulfur atoms. Lanthionine bonds contain only one sulfur atom. The disulfide bonds that are broken by hydroxide relaxers are broken permanently and can never be re-formed. That is why hair that has been treated with a hydroxide relaxer is unfit for permanent waving and will not hold curl.


Metal hydroxide relaxers

  • Are ionic compounds formed by a metal—sodium (Na), potassium (K), or lithium (Li)—which is combined with oxygen (O) and hydrogen (H). Metal hydroxide relaxers include sodium hydroxide (NaOH), potassium hydroxide (KOH), and lithium hydroxide (LiOH).

The hydroxide ion is the active ingredient in all hydroxide relaxers

Lye-based relaxers

  • Sodium hydroxide (NaOH) relaxers are commonly called lye relaxers.
  • Sodium hydroxide is the oldest, and one of  the most common, types of chemical hair relaxer.

Sodium hydroxide is also known as lye or caustic soda and can cause hair loss and skin burns if used incorrectly

No-lye relaxers

  • Lithium hydroxide (LiOH) and potassium hydroxide (KOH) relaxers are often advertised and sold as “no mix—no lye” relaxers. Although technically they are not lye, their chemistry is identical, and there is very little difference in their performance.

Guanidine hydroxide relaxers

  • Also advertised and sold as no-lye relaxers.
  • Hydroxide ion is still active ingredient.
  • Require two components which must be mixed.
  • Straighten hair completely.
  • Less scalp irritation than other Hydroxide relaxers.
  • Recommended for sensitive scalps.
  • Sold over-the-counter.
  • Do not reduce hair damage.

They swell hair slightly more than other hydroxide relaxers and are also more drying to the hair

Low-pH relaxers

  • Sulfites and bisulfites; they are marketed as mild alternative relaxers. They are compatible with thio relaxers but not compatible with hydroxide relaxers. They do not completely straighten extremely curly hair. Low pH relaxers are intended for use on color-treated hair.


Hydroxide relaxers are usually sold in base and no-base formulas.

Base cream

  • Also known as protective base cream, is an oily cream used to protect the skin and scalp during hair relaxing.
  • Base relaxers require the application of a protective base cream to the entire scalp prior to the application of the relaxer.

No-base relaxers

  • Do not require the application of a protective base cream. They contain a protective base cream that is designed to melt at body temperature.
  • As the relaxer is applied, body heat causes the protective base cream to melt and settle out onto the scalp in a thin, oily, protective coating.
  • No-base relaxers are an improvement only on the protection that is provided to the skin by the oils in all hydroxide relaxers.
  • For added protection, protective base cream should always be applied to the entire scalp, hairline, and around the ears, even with no-base relaxers.
  • Caution! Extreme damage can occur if thio or hydroxide relaxers are applied to hair that has been colored with products containing metallic salts.


  • An acid–alkali neutralization that neutralizes (deactivates) the alkaline residues left in the hair by a hydroxide relaxer and lowers the pH of the hair and scalp; hydroxide relaxer neutralization does not involve oxidation or rebuilding disulfide bonds.
  • Hair remains at high pH.
  • Acid-balanced shampoo used.

Rinsing alone will not neutralize the relaxer. An acid-balanced shampoo or normalizing lotion neutralizes the remaining hydroxide ions


  • Although the same procedure is used for all hydroxide relaxers, application methods vary according virgin and retouch application.
  • Virgin relaxer application: A virgin relaxer application should be used for hair that has not had previous chemical relaxer service.
  • A retouch relaxer application: A retouch relaxer application should be used for hair that has previously received a chemical relaxer service.
  • Texturizing service: A texturizing service uses a hydroxide relaxer to reduce the curl pattern by degrees using a mild strength relaxer.
  • Using base cream, protective cream, and normalizing products: Most relaxers today recommend the application of a base cream to protect the entire scalp, irrespective of a virgin application or retouch.
  • Neutralizing shampoo: An acidic shampoo designed to restore the natural pH of hair and scalp.



  • Perform a thorough hair analysis and client consultation prior to the service.
  • Examine the scalp for abrasions. Do not proceed with the service if redness, swelling, or skin lesions are present.
  • Keep accurate and detailed client records of the services performed and the results achieved.
  • Have the client sign a release statement indicating that he or she understands the possible risks related to the service.
  • Do not apply a hydroxide relaxer on hair that has been previously treated with a thio relaxer.
  • Do not apply a thio relaxer or soft curl perm on hair that has been previously treated with a hydroxide relaxer.
  • Do not chemically relax hair that has been treated with a metallic dye.
  • Do not relax overly damaged hair. Suggest instead a series of reconstruction treatments.
  • Do not shampoo the client prior to the application of a hydroxide relaxer.
  • The client’s hair and scalp must be completely dry and free from perspiration prior to the application of a hydroxide relaxer.
  • Apply a protective base cream to avoid scalp irritation.
  • Wear gloves during the relaxer application.
  • Protect the client’s eyes.
  • If any solution accidentally gets into the client’s eye, flush the eye immediately with cool water and refer the client to a doctor.
  • Do not allow chemical relaxers to come into contact with the client’s ears, scalp, or skin.
  • Perform periodic strand tests to see how fast the natural curls are being removed.
  • Avoid scratching the scalp with your comb or fingernails.
  • Do not allow the application of a relaxer retouch to overlap onto previously relaxed hair.
  • Never use a strong relaxer on fine or damaged hair. It may cause breakage.
  • Do not attempt to remove more than 80 percent of the natural curl.
  • Thoroughly rinse the chemical relaxer from the hair. Failure to rinse properly can cause excessive skin irritation and hair breakage.
  • Use a normalizing lotion to restore the hair and scalp to their normal acidic pH.
  • Use a neutralizing shampoo with a color indicator to guarantee that the hair and scalp have been restored to their normal pH.
  • Use a conditioner and wide-tooth comb to eliminate excessive stretching when combing out tangles.
  • Do not use hot irons or excessive heat on chemically relaxed hair.


Posted by: Opeyemi Aduroja; a Chemist/ imageCalibration Technician at Applied Analytical Systems Litd., 8, Atunwa Street, Ikeja, Lagos, Nigeria. Phone (234) 8068129603, email: [email protected]



This Post Has One Comment

  1. hey does chemically treated hair i mean rebounding or smoothing creates any waterproof layers on our hair?

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