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I was recently asked what the difference is between Castile Soap and Lye Soap. And that question actually doesn’t work. Castile soap is named based on the type of ingredients, one of which is lye. Most all soaps contain lye because this is what make soap…well soap.
True Castile soap is made solely from olive oil. It gets its name from the region in Spain called Castile, where olives are prevalent. Original Castile soap was made from Olive Oil and Laurel Oil. As the Castile process for soap making spread (through various conquests and wars in middle age Europe), it changed to a primarily Olive Oil based soap since Laurel Oil was not very common in other areas.
Now, you will find many Castile soaps that use various vegetable oils. Olive oil, palm oil, and coconut oil are a few of my favorites. As long as it does not have any animal fats, Castile can be applied to the name. Before Castile soap spread to other regions, soap was made using tallow or lard. Even today, some prefer tallow in their soap because it is an excellent hardening agent. If you were to use straight Olive Oil, you will have to let the soap age for quite a long time in order for it to harden into a useable bar.
Simply stated, you need an oil or fat mixed with lye to create soap. Refreshing your High School Chemistry, the oil or fat is the acidic component and the lye is the base component. Mixing the two creates a chemical reaction that neutralizes them into soap. If made correctly you will not have any issues with the lye being a caustic material. It will burn the skin if not neutralized!
As I pointed out above, lye is essential to soap making. There are two types of lye that can be used for soap. Potassium Hydroxide is used more often in liquid Castile soaps, like Dr. Bronner’s . I use a ready-to-go powder of Sodium Hydroxide in my soaps. Both will create equally good soap.
You can also make your own lye. The process of making lye doesn’t seem too difficult, but it is definitely for the hard core DIY-er. The main component of making lye is ashes. Since I don’t usually have a pile of nice hardwood ashes lying about, I have not attempted making lye myself. There are good instructions on how to make it here.
One thing that makes homemade soaps more beneficial to use than commercial soaps, is that they retain glycerin. Glycerin is a byproduct of the lye/oil reaction. This byproduct is what creates the soft, soothing effect of homemade soaps. Many commercial soap makers remove the glycerin. They sell this glycerin separately for additional profits. (My theory is that they purposefully make their soap to dry out your skin so that you also have to buy the lotion that they make. Just my tin foil showing through.)
So now that you know a little bit more about soap and what it is made out of, you can make an educated decision in what kind of soap you buy. Of course I would LOVE if you always bought my handcrafted soaps. But I’m not writing this to ask you to do that. There are plenty of wonderful soaps made by small soap makers like me that you can support. Many that make much better soap than I do, as I am still learning.
Choosing a handcrafted Castile soap will be better for your skin and body in general. Most handcrafted soaps will not contain any of the unnecessary harsh chemicals that commercial soaps use. Making them truly moisturizing and refreshing. Your skin is your largest organ and what you put on it does end up in your body. Be choosy in what you apply on the outside so that it doesn’t negatively effect the inside!
Do you use Castile soap?
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