photo of surfactants: conditioning agents, cleansing agents, emulsifiers, solubilizers
What is a Surfactant?
A surfactant is a surface-active agent. Surfactants alter and reduce the surface tension of the solution. Water has an inherent property of surface. It has a high surface tension.
If you were to drop water with an eyedropper onto a slide and look at the droplet under the microscope from the side you would see a spherical outline, a round drop. If you add surfactant to this drop of water, the drop would go down and spread over the glass. This makes the water more soluble. By adding a surfactant to the water, it makes the surface of water more soluble by flattening it out and allows other ingredients to dissolve into it.
If a duck is floating in water and a surfactant is added to the water and the duckling feathers get wet, the duck will sink.
Surfactants have many purposes and the performance depends on their function.
Types and Functions of Surfactants
- Conditioning Agents (conditioner used in hair conditioner, lotion, cream)
- Detergents (cleansing used in shampoo, hand soap, facial wash, body wash)
- Emulsification Agent (emulsifier used in hair conditioner, lotion, cream)
- Solubilization (solubilizer used in hair mists, body mists, room mists)
Surfactants are classified by their charge. It is vital to know the type of surfactant and the compatibility with other ingredients in the formulation and to perform properly in the formulation.
Classification of Surfactants
- Anionic – negative charge
- Cationic – positive charge (ionized positive charge)
- Nonionic – neutral
- Amphoteric – positive and negative (positive in acidic environments and negative in alkaline environments)
- Shampoo surfactants are not good emulsifiers. They do not tolerate oil and the oil will separate out of the water.
- If a product contains an emulsifier, it is technically not surfactant-free.
- Generally, when referring to surfactants it refers to cleansers, detergents.
The next upcoming posts will be on the function of each type of surfactant. See, What is an Emulsifier? here.
Joan Morais is a natural cosmetic formulator, instructor, author and the owner of Joan Morais Naturals. Joan assists product makers on how to make high quality, stable and effective natural body, hair and skin care products for personal use and a product making business.