What is the difference between Castile and Bastille soap?
Other than spelling?
The difference is in the oil/fat components of the recipes.
As you know, soap is made of lye, water, and oils/fats/butters.
Castile soap named after its place of origin. Castile region of Spain was a well-known soap making center. Castile soap has only one oil component.
– It is made with 100% olive oil.
Pure olive oil makes Castile soap very different from soaps familiar to us. Castile soap does not lather in the same way as soaps that are made with combination of oils. Castile soap doesn’t produce bubbles. Instead, it feels very creamy when lathered. It’s not a bad quality. Some people like it more than bubbly soap, some don’t. It’s just the way it is.
In fact, excess bubbles in soaps strip off too much fats from the skin making skin too dry. This is because soap acts as a surfactant. Olive oil in soap moisturizes skin with each use. Olive oil also hardens cured cold processed soap or hot processed soap.
Castile soap is excellent for curing dry skin, eczema, or psoriasis. It makes very a good baby soap.
Some people want more bubbles though. So they invented Bastille soap. This name of soap was coined by soap makers to denote a deviation from a pure olive oil Castile soap.
Bastille soap is made with mostly olive oil (no less than 70%) with minor additions of other oils/fats/butters.
Since Bastille soap has mostly olive oil, it will still have the characteristics close to those of Castile soap. It will be hard, long lasting, moisturizing, and with stable lather. Other qualities of Bastille soap will depend on the other oils used.
Bastille soap is often made with coconut oil and/or castor oil for bubbles, and palm oil.