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The Historical Roots and Beneficial Properties of Soap - A look into Castile & Bastile Soap

Castile soap is an extraordinary natural cleaner with a rich history that dates back to the early kingdoms of Spain. Originating in the Castile region, hence the name, this soap has been prized for centuries due to its unique properties. From cold and hot process soap-making methods to water discounting options, the making of Castile soap has been refined over the years, ultimately providing an environmentally friendly and versatile product.

A Journey through Castile Soap's History

Castile soap's origins can be traced back to the Levant, where Aleppo soap-makers had for centuries been using laurel oil and olive oil to produce their famous soaps. The crusaders brought this soap-making technique to Europe during the 11th century, where it spread across the continent.

When the craft reached the Castile region of Spain, which was rich in olive oil but lacked laurel oil, soap-makers began producing a simple, pure soap made only from olive oil, water, and lye, thereby marking the birth of Castile soap.

Properties of Castile Soap

Castile soap's unique properties come from the primary ingredient used: olive oil. Olive oil contains oleic acid, which gives the soap its characteristic moisturizing properties. Castile soap is gentle on the skin, making it a preferable option for individuals with sensitive skin conditions such as eczema or psoriasis.

Another distinguishing property of Castile soap is its biodegradability. Unlike many commercial soaps, Castile soap is eco-friendly, and it breaks down safely and naturally in the environment. This makes it a popular choice for those seeking to reduce their environmental footprint.

Additionally, Castile soap is highly versatile. It can be used for a wide range of cleaning purposes, from body wash, shampoo, and shaving cream to dish soap, laundry detergent, and even general house cleaning.

Variance: Bastile Soap

While traditional Castile soap is made entirely from olive oil, a variant known as Bastile soap incorporates other oils into the recipe. The term "Bastile" is a portmanteau of "Castile" and "Bastard", cheekily acknowledging that while it's not pure Castile soap, it's still primarily made with olive oil—typically around 70%, with the remaining 30% comprising other oils like coconut or palm oil.

The inclusion of these other oils enhances the lathering and cleansing properties of the soap. While pure olive oil soap is incredibly mild and moisturizing, it doesn't lather as well as soaps made with other oils. Bastile soap, therefore, provides a happy medium between the gentle, nourishing properties of Castile soap and the rich lather of other handmade soaps.

Soap-Making Processes: Cold vs. Hot Process

When it comes to making Castile or Bastile soap, there are two primary methods: cold process and hot process.

Cold process soap-making is a chemical reaction where sodium hydroxide (lye) interacts with fats (oils). This method involves mixing oils and lye solution at a particular temperature, blending to 'trace', then pouring the mixture into a mold, where the soap hardens and saponifies over 24 hours. After this, the soap needs to cure for about 4-6 weeks before use. This allows for the evaporation of water, ensuring a harder, longer-lasting bar of soap.

The hot process, on the other hand, accelerates saponification by adding heat. The mixture is cooked, often in a slow cooker, speeding up the saponification process. This results in a soap that is safe to use as soon as it cools and hardens, although some soap makers prefer to allow a week or two of cure time.

The Water Discount Option

Both cold and hot processes allow for a technique known as water discounting. This method involves reducing the amount of water used in the soap-making process. It hastens the curing time and results in a harder bar, which lasts longer.

A water to lye ratio of 1.5 to 1 is quite common for water discounting, meaning that for every 1 part of lye, 1.5 parts of water are used. Reducing water can be especially beneficial when making Castile soap, which typically requires a longer curing time due to the high amount of olive oil.

Keep in mind, however, that water discounting can speed up the 'trace' in the cold process and shorten the overall working time. Also, it can lead to a more brittle bar if the water content becomes too low. Therefore, it's crucial to strike a balance to ensure the best soap quality.


In conclusion, the history of Castile soap and its variant, Bastile soap, is as rich as the soaps themselves. From their origins in the Castile region of Spain to their modern variations and methods of production, these soaps continue to provide a natural, environmentally friendly, and versatile cleaning solution. Whether you're making it through the cold process or hot process, or using a water discounting technique, Castile and Bastile soaps remain cherished for their unique properties and the sustainable lifestyle they promote.

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Thank you John!

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