Difference between castile soap and other liquid soap
I was chatting to a customer this week about castile soap, and she asked a very good question. What is the difference between castile soaps and other liquid soaps?
What is castile soap?
Castile soaps are made from vegetable oil, rather than animal fats or synthetics. They originally came from Spain, from the Castile region. Castile soaps always used to be made with olive oil, but nowdays they can be made with any plant based fat. You’ll find coconut, jojoba, hemp oil, palm oil and more.
Castile soaps come in both solid and liquid forms. Taking Dr Bronner as an example, you’ll find that their range includes bar soaps and liquid soaps. Both of these are castile soaps. The difference between a bar and a liquid castile soap is the chemical that’s used to change the fat into soap. This process is called saponification.
Liquid soaps use potassium hydroxide to saponify, and bar soaps use sodium hydroxide (lye). Although the potassium hydroxide and sodium hydroxide are both highly caustic, the chemical process of saponification completely removes these chemicals. Through the magic of chemistry, you’re left with a mixture of water, soap and glycerin.
Castile soaps are pure, safe and can be formulated with extra oils to make them moisturising, rather than drying, on your skin. Adding the extra oils is called superfatting.
What are other soaps made from?
Whereas a castile soap is made from plant based fats and oils, other natural soaps are made from animal fats like lard or tallow.
If a liquid soap isn’t made with either plant or animal based fats, they’re not soaps at all, they’re detergents. Detergents are different to soaps in that they’re often synthetic and they work slightly differently.
What is a detergent? A detergent is based on surfactants, which are generally synthetic, but can also be derived from natural sources (cocamidopropyl betaine is derived from coconuts, for example). This doesn’t make them natural, as they’re still heavily processed, but they do come from natural sources.
How to tell the difference between soaps and detergents?
Liquid soaps will list potassium hydroxide, bar soaps will list sodium hydroxide in their ingredients lists. Detergents will use some kind of surfactant. These might be naturally derived, like cocoamidopropyl betaine or polyglucoside. Or they could be synthetic, like sodium lauryl sulfate (SLS).
So if you’re seeing ‘soaps’ with surfactants in them, they’re actually detergents. Generally, shower gels, liquid hand soaps are detergents rather than soaps.
Should you use a soap or a detergent?
Castile soaps are made from natural ingredients, that are pretty simple, and break down easily in the environment. There are lots of ways you can use castile soaps, so you can cut down on the amount of products that you’re using.
If you’re in an area that has hard water, you may find that soap doesn’t work very well. The high amount of calcium in hard water reacts with the soap to form a scum. This stops the surfactant properties, so it doesn’t foam up as easily. You use more soap to make up for this and end up with a film of scum on your tiles and sink. You’ll probably find that using a detergent based cleanser designed for hard water areas will give you a better result.
You may also find that soap irritates sensitive skin, especially facial skin. Finding a sensitive skin cleanser that is detergent based might be a better choice. This is why you’ll sometimes see products that are advertised as being ‘soap free’.
It also depends on what you’re using the product for. You may choose to use a castile soap for personal cleansing, but stick to detergents for household cleaning. (Although Dr Bronner does say that you can use castile soap for just about everything!).
The key, as always, is to read the ingredients on the back of the label. Ignore the marketing claims on the front and find out what’s really in the products that you’re using.
Image credit: AlexKosov/Depositphotos
Do you know what the ‘soap’ that you’re using is made from? Share your thoughts below!
Get the latest posts straight to your inbox every week!