Shampoos are cleaning formulations used for a wide range of applications, including personal care, pet use, and carpets. Most are manufactured in roughly the same manner. They are composed primarily of chemicals called surfactants that have the special ability to surround oily materials on surfaces and allow them to be rinsed away by water. Most commonly, shampoos are used for personal care, especially for washing the hair.
Before the advent of shampoos, people typically used soap for personal care. However, soap had the distinct disadvantages of being irritating to the eyes and incompatible with hard water, which made it leave a dull-looking film on the hair. In the early 1930s, the first synthetic detergent shampoo was introduced, although it still had some disadvantages. The 1960s brought the detergent technology we use today.
Over the years, many improvements have been made to shampoo formulations. New detergents are less irritating to the eyes and skin and have improved health and environmental qualities. Also, materials technology has advanced, enabling the incorporation of thousands of beneficial ingredients in shampoos, leaving hair feeling cleaner and better conditioned.
New shampoos are initially created by cosmetic chemists in the laboratory. These scientists begin by determining what characteristics the shampoo formula will have. They must decide on aesthetic features such as how thick it should be, what color it will be, and what it will smell like. They also consider performance attributes, such as how well it cleans, what the foam looks like, and how irritating it will be. Consumer testing often helps determine what these characteristics should be.
Once the features of the shampoo are identified, a formula is created in the laboratory. These initial batches are made in small beakers using various ingredients. In the personal care industry, nearly all of the ingredients that can be used are classified by the Cosmetic, Toiletry, and Fragrance Association (CTFA) in the governmentally approved collection known as the International Nomenclature of Cosmetic Ingredients (INCI). The more important ingredients in shampoo formulations are water, detergents, foam boosters, thickeners, conditioning agents, preservatives, modifiers, and special additives.
The primary ingredient in all shampoos is water, typically making up about 70-80% of the entire formula. Deionized water, which is specially treated to remove various particles and ions, is used in shampoos. The source of the water can be underground wells, lakes, or rivers.
The next most abundant ingredients in shampoos are the primary detergents. These materials, also known as surfactants, are the cleansing ingredients in shampoos. Surfactants are surface active ingredients, meaning they can interact with a surface. The chemical nature of a surfactant allows it to surround and trap oily materials from surfaces. One portion of the molecule is oil compatible (soluble) while the other is water soluble. When a shampoo is applied to hair or textiles, the oil soluble portion aligns with the oily materials while the water soluble portion aligns in the water layer. When a number of surfactant molecules line up like this, they form a structure known as a micelle. This micelle has oil trapped in the middle and can be washed away with water, thus giving the shampoo its cleansing power.
Surfactants are derived from compounds known as fatty acids. Fatty acids are naturally occurring materials which are found in various plant and animal sources. The materials used most often to make the surfactants used in shampoos are extracted from coconut oil, palm kernel oil, and soy bean oil. Some common primary detergents used in shampoos are ammonium lauryl sulfate, sodium lauryl sulfate, and sodium lauryl ether sulfate.
In addition to cleansing surfactants, other types of surfactants are added to shampoos to improve the foaming characteristics of the formulation. These materials, called alkanolamides, help increase the amount of foam and the size of the bubbles. Like primary detergents, they are also derived from fatty acids and have both water soluble and oil soluble characteristics. Typical materials include lauramide DEA or cocamide DEA.
To some extent, the alkanolamides that make shampoos foam also make the formulations thicker. However, other materials are also used to increase the viscosity. For example, methylcellulose, derived from plant cellulose, is included in shampoos to make them thicker. Sodium chloride (salt) also can be used to increase shampoo thickness.
Some materials are also added to shampoos to offset the sometimes harsh effect of surfactants on hair and fabrics. Typical conditioning agents include polymers, silicones, and quaternary agents. Each of these compounds deposit on the surface of the hair and improve its feel, softness, and combability, while reducing static charge. Shampoos that specifically feature conditioning as a benefit are called 2-in-1 shampoos because they clean and condition hair in the same step. Examples of conditioning agents include guar hydroxypropyltrimonium chloride which is a polymer, dimethicone which is a silicone, and quatemium 80, a quatemary agent.
Since shampoos are made from water and organic compounds, contamination from bacteria and other microbes is possible. Preservatives are added to prevent such growth. Two of the most common preservatives used in shampoos are DMDM hydantoin and methylparaben.
Other ingredients are added to shampoo formulas to modify specific characteristics. Opacifiers are added to make the formula opaque and give it a pearly look. Materials known as sequestering agents are added to offset the dulling effects of hard water. Acids or bases such as citric acid or sodium hydroxide are added to adjust the pH of a shampoo so the detergents will provide optimal cleaning.
One of the primary factors that influence the purchase of a shampoo is its color and odor. To modify these characteristics, manufacturers add fragrance oils and governmentally approved and certified FD&C dyes. Other special additives can also have a similar effect. Natural materials such as botanical extracts, natural oils, proteins, and vitamins all impart special qualities and help sell shampoos. Additives such as zinc pyrithione are included to address the problem of dandruff. Other additives are dyes which can color the hair.
After a shampoo formula is developed, it is tested to ensure that its qualities will minimally change over time. This type of testing, called stability testing, is primarily used to detect physical changes in such things as color, odor, and thickness. It can
The manufacturing process can be broken down into two steps. First a large batch of shampoo is made, and then the batch is packaged in individual bottles.
- 1 Large batches of shampoo are made in a designated area of the manufacturing plant. Here workers, known as compounders, follow the formula instructions to make batches that can be 3,000 gal (11,000 1) or more. Raw materials, which are typically provided in drums as large as 55 gal (200 1) or in 50-lb (23-kg) bags, are delivered to the compounding area via forklift trucks. They are poured into the batch tank and thoroughly mixed.
2 Depending on the formula, these batches can be heated and cooled as
necessary to help the raw materials combine more quickly. Some raw
materials such as water or the primary detergents are pumped and metered
directly into the batch tank.
Quality control check
- 3 After all the ingredients are added to the batch, a sample is taken to the Quality Control (QC) lab for testing. Physical characteristics are checked to make sure the batch adheres to the specifications outlined in the formula instructions. The QC group runs tests such as pH determination, viscosity checks, and appearance and odor evaluations. They can also check the amount of detergent that is in the formula and whether there is enough preservative. If the batch is found to be "out of spec," adjustments can be made. For instance, acids or bases can be added to adjust the pH, or salt can be added to modify the viscosity. Colors can also be adjusted by adding more dye.
- 4 After a batch is approved by QC, it is pumped out of the main batch tank into a holding tank where it can be stored until the filling lines are ready. From the holding tank it gets pumped into the filler, which is made up of a carousel of piston filling heads.
- 5 At the start of the filling line, empty bottles are put in a large bin called a hopper. Here, the bottles are physically manipulated until they are correctly oriented and standing upright. They are then moved along a conveyor belt to the filling carousel, which holds the shampoo.
- 6 The filling carousel is made up of a series of piston filling heads that are calibrated to deliver exactly the correct amount of shampoo into the bottles. As the bottles move through this section of the filling line, they are filled with shampoo.
- 7 From here the bottles move to the capping machine. Much like the bin that holds the empty bottles, the caps are also put in a hopper and then correctly aligned. As the bottles move by the caps are put on and twisted tight.
- 8 After the caps are put on, the bottles move to the labeling machines (if necessary). Depending on the type of labels, they can either be stuck on using adhesives or heat pressed. Labels are stuck to the bottles as they pass by.
- 9 From the labeling area, the bottles move to the boxing area, where they are put into boxes, typically a dozen at a time. These boxes are then stacked onto pallets and hauled away in large trucks to distributors. Production lines like this can move at speeds of about 200 bottles a minute or more.
In addition to the initial checks to make sure the product meets specifications, other quality control checks are made. For example, line inspectors watch the bottles at specific points on the filling line to make sure everything looks right. They notice things like fill levels, label placement, and whether the cap is on correctly. The product is also routinely checked to see if there has been any microbial contamination. This is done by taking a bottle off the filling line and sending it to the QC lab. Here, a small amount of the shampoo product is smeared onto a plate and inoculated with bacteria and other organisms to see if they grow. Additionally, the packaging is also checked to see if it meets specifications. Things such as bottle thickness, appearance, and bottle weight are all checked.
Consumer product corporations will continue to manufacture new types of shampoos. These new formulas will be driven by ever-changing consumer desires and developing chemical technology. Currently, consumers like multi-functional shampoos, such as 2-in-I shampoos, which provide cleansing and conditioning in one step, or shampoos that aid in styling. New shampoos will likely provide improved conditioning, styling, and coloring while cleaning the hair.
Shampoo technology will also improve as new ingredients are developed by raw material suppliers. Some important advances are being made in the development of compounds such as polymers, silicones, and surfactants. These materials will be less irritating, less expensive, more environmentally friendly, and also provide greater functionality and performance.
Where to Learn More
Knowlton, John and Steven Pearce. The Handbook of Cosmetic Science and Technology. Elsevier Science Publishers, 1993.
Umbach, Wilfried. Cosmetics and Toiletries Development, Production, and Use. Ellis Horwood, 1991.
Kintish, Lisa. "Shampoos Get Specific." Soap/Cosmetic/Chemical Specialties, October 1995, pp. 20-30.
— Perry Romanowski