This is a copy of the notes for a class I am teaching at the SCA event Lilies War. It is a very brief overview of soap making history. I plan to do a more detailed class in the future as my research continues.
History of soap and lye making
Lecture by Antonia Stefani
What is soap? Soap is a chemical compound created by combining fats or oils (fatty acids) with an alkaline solution, like lye. It acts as a surfactant, allowing water to mix with oil and grease so they can be easily rinsed away.
The History of Soap:
The exact origins of soap as we know it today are difficult to determine. There are references in Sumerian, Babylonian (2800 BC) and Egyptian texts to soap like substances, indicating that the properties of fats and alkali were understood even then. It is another 2000 years before Greek and Roman texts mention soap. Interestingly, soap was not used for bathing at that time, but for washing clothing. To bathe, they would coat their bodies with oil and scrape off dirt and dead skin with a tool called a strigil.
From there, ingredients and recipes were refined and the countries around the Mediterranean, where olive oil was plentiful, began making soap. Fats used could be tallow from sheep, goats and pigs; or olive oil. Lye came from ashes of hard woods and sea weed.
In the middle ages, hard bars of soap such as we know today began to be produced. The first was Aleppo soap, made from olive and laurel oil, which is still made in Syria. Video: https://www.youtube.com/watch?v=98mayEp4rxE
Castile soap was originally made in the Castile region of Spain. It was a pure olive oil soap, known for being mild and gentle. You can read more about it and how it came to the US in the 1940’s here: https://www.lisabronner.com/the-history-of-castile-soap/
Historical Centers of Soap Making Guilds
By the 17th century, soapmakers’ guilds had become established institutions throughout Europe . These organizations regulated the craft’s secrets, carefully guarding production techniques and controlling quality standards. The training and promotion of craftsmen within the trade were highly regulated, with knowledge passed meticulously from master to apprentice.
Guild formation had begun much earlier in some regions—Naples had organized soapmakers as early as the late sixth century . In fact, Charlemagne’s Capitulare De Villis, dating to approximately 800 CE, specifically mentions soap as one of the products royal estate stewards were required to inventory .
Throughout the 13th century, soapmaking in Britain became concentrated in large towns like Bristol, Coventry, and London, with each developing distinctive local varieties . The profession gained such prominence that Richard of Devizes noted around 1200 CE that virtually everyone in Bristol was or had been a soapmaker .
Making Lye:
The Leaching Process
Testing and Concentrating Strength
Because homemade lye varies in strength, you must test its concentration before using it for tasks like soap making.
Important Safety Reminders
Resources:
Video by Sally Pointer, experimental archeologist: https://www.youtube.com/watch?v=B5KLWPSMot8
Journal article: https://exarc.net/issue-2024-3/at/experimental-exploration-earliest-soapmaking
Blog post : https://ravensroots.org/blog/makinglye
History of soap and lye making
Lecture by Antonia Stefani
What is soap? Soap is a chemical compound created by combining fats or oils (fatty acids) with an alkaline solution, like lye. It acts as a surfactant, allowing water to mix with oil and grease so they can be easily rinsed away.
The History of Soap:
The exact origins of soap as we know it today are difficult to determine. There are references in Sumerian, Babylonian (2800 BC) and Egyptian texts to soap like substances, indicating that the properties of fats and alkali were understood even then. It is another 2000 years before Greek and Roman texts mention soap. Interestingly, soap was not used for bathing at that time, but for washing clothing. To bathe, they would coat their bodies with oil and scrape off dirt and dead skin with a tool called a strigil.
From there, ingredients and recipes were refined and the countries around the Mediterranean, where olive oil was plentiful, began making soap. Fats used could be tallow from sheep, goats and pigs; or olive oil. Lye came from ashes of hard woods and sea weed.
In the middle ages, hard bars of soap such as we know today began to be produced. The first was Aleppo soap, made from olive and laurel oil, which is still made in Syria. Video: https://www.youtube.com/watch?v=98mayEp4rxE
Castile soap was originally made in the Castile region of Spain. It was a pure olive oil soap, known for being mild and gentle. You can read more about it and how it came to the US in the 1940’s here: https://www.lisabronner.com/the-history-of-castile-soap/
Historical Centers of Soap Making Guilds
- Naples, Italy: Appeared in the late 6th century. Known as the earliest organized soap boilers in Europe.
- Castile, Spain: Famous for Almonas (soap factories) operating under royal monopoly, setting the standard for olive-oil-based Castile soap.
- Marseille, France: Emerged in the 9th century, later dominating Mediterranean production using strict 72% vegetable oil edicts.
- Bristol, England: 13th-century hub utilizing local tallow and the river network for large-scale distribution.
By the 17th century, soapmakers’ guilds had become established institutions throughout Europe . These organizations regulated the craft’s secrets, carefully guarding production techniques and controlling quality standards. The training and promotion of craftsmen within the trade were highly regulated, with knowledge passed meticulously from master to apprentice.
Guild formation had begun much earlier in some regions—Naples had organized soapmakers as early as the late sixth century . In fact, Charlemagne’s Capitulare De Villis, dating to approximately 800 CE, specifically mentions soap as one of the products royal estate stewards were required to inventory .
Throughout the 13th century, soapmaking in Britain became concentrated in large towns like Bristol, Coventry, and London, with each developing distinctive local varieties . The profession gained such prominence that Richard of Devizes noted around 1200 CE that virtually everyone in Bristol was or had been a soapmaker .
Making Lye:
The Leaching Process
- Prepare the Ashes: Sift out large unburnt chunks of wood, keeping only the fine white and grey ash.
- Set Up a Filter: Use a bucket with a small hole drilled in the bottom. Layer the bottom with clean stones or straw, then cover with a piece of cotton cloth (like an old T-shirt) to act as a filter.
- Pack the Ash: Fill the bucket with ashes, packing them down tightly to slow the water's descent for better leaching.
- Add Water: Create a small depression in the top of the ashes and slowly pour in your soft water.
- Collect the Liquid: Place a "safe" container (plastic or glass) under the hole. The liquid that drips out—a brown, tea-colored fluid—is your raw lye water.
- Recirculate: For a stronger concentration, pour the collected lye water back through the ashes multiple times.
Testing and Concentrating Strength
Because homemade lye varies in strength, you must test its concentration before using it for tasks like soap making.
- The Egg Test: Carefully lower a fresh, room-temperature egg into the solution.
- Weak: The egg sinks.
- Ideal: The egg floats with a quarter-sized (or nickel-sized) portion showing above the surface.
- Boiling Down: If the lye is too weak, you can concentrate it by boiling it slowly in a stainless steel or glass pot to evaporate excess water. Do this in a well-ventilated area.
Important Safety Reminders
- Causticity: Lye made this way is extremely alkaline (pH ~13). It will dissolve skin and natural fibers upon contact.
- Contamination: Only use ash from clean, untreated wood. Burning plastics, painted wood, or electronics produces toxic ash that should never be used.
Resources:
Video by Sally Pointer, experimental archeologist: https://www.youtube.com/watch?v=B5KLWPSMot8
Journal article: https://exarc.net/issue-2024-3/at/experimental-exploration-earliest-soapmaking
Blog post : https://ravensroots.org/blog/makinglye
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