Mo wants to know…I’m confused. Since I read that surfactant-based liquid cleansers are better than soap, I have been on the look out for a good body wash preferably fragrance free. But now I discover that Dove Bar / Vanicream Bar etc. are not soap but Syndets. What does that mean? There are also Syndet base Liquid face & body washes. What do I pick up?
Right Brain comes clean: It’s easy to understand why people get confused by terms like soap, surfactant and syndet. Personal care marketing companies often hijack words from science and repackage them as friendly marketing messages. Unfortunately, everyone’s marketing message is different so words lose their focused definitions. That’s what has happened with these words. We’ll try to clear it up – busting beauty myths like this is what we do best!
Surfactant Cleaners
Almost all cleansing products are based on surfactants. These molecules have a special construction which makes them compatible with both oils and water. Since oil and water do not usually mix, you need surfactants to remove oils from skin and hair. Soaps and syndets are all surfactants. Detergent is just a synonym for surfactant.
Syndet Made Simple
Syndet is a portmanteau word created by combining the words “synthetic” and “detergent”. It was made up by the beauty industry to make products based on synthetic detergents sound sciencey and special. Synthetic detergent sounds nasty, dangerous and icky. Syndet sounds high tech, fun and friendly.
A common type of Syndet like Sodium Lauryl Sulfate is made by reacting a fatty alcohols with acid.
Fatty Alcohol + Acid = Syndet
Straight Dope on Soap
Soaps were the first surfactants people used for cleaning. They are made by reacting fatty acids with a base (e.g. sodium hydroxide), a process called saponification.
Fatty Acid + Base = Soap
Three things make Soap different from Syndets.
1. Starting material. The starting material for soap is either animal fat (tallow) or natural oils. Syndets start with fatty alcohols which can be distilled from petroleum or derived from natural oils. Sodium Lauryl Sulfate can be made from both Coconut Oil or petroleum distillates. A by-product of soap making is glycerin, a natural moisturizer. Syndets must be formulated with glycerin or other moisturizing ingredients.
2. Reactions with metal ions. The primary problem with soap is that it reacts with metal ions to form a material that is insoluble (can’t be dissolved) in water. This is what causes the “soap scum” you see lining people’s bathtubs and sinks. Syndets do not react like this so it is not a problem.
3. Formulating flexibility. From a formulation standpoint, syndets are much more flexible than soaps. Soaps are generally solids at room temperature and are limited in the number of ingredients you can incorporate in them. Syndets are liquids that can be thickened and made solid.
Syndet Bar
An example of a Syndet bar would be this La Roche-Posay Syndet bar.
It uses standard surfactants like Disodium Cocoamphodiacetate, Coco-Betaine, Peg-7 Glyceryl Cocoate, Sodium Laureth Sulfate, etc.
Beauty Brains Bottom Line
As far as what you should get, that is up to you. If fragrance free is an issue, you could try the La Roche product. You could also try the Dove Bar or other syndet bar. The key to these things is to try different products until you find something you like. Everyone’s skin and preferences are different. Personal experimentation is your best option.
See this page for an experiment demonstrating the difference between soap and detergent.
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