All over the world, for all of human history – and probably going back to our earliest hominid ancestors – people have found ways to try to keep themselves clean. But how did soap come about?

Research:

• “Soap, N. (1), Etymology.” Oxford English Dictionary, Oxford UP, June 2025, https://doi.org/10.1093/OED/1115187665.
• American Cleaning Institute. “Soaps & Detergents History.” https://www.cleaninginstitute.org/understanding-products/why-clean/soaps-detergents-history
• Beckmann, John. “History of Inventions, Discoveries and Origins.” William Johnston, translator.
• Bosart, L.W. “The Early History of the Soap Industry.” The American Oil Chemists' Society. Journal of Oil & Fat Industries 1924-10: Vol 1 Iss 2.
• Cassidy, Cody. “Who Discovered Soap? What to Know About the Origins of the Life-Saving Substance.” Time. 5/5/2020. https://time.com/5831828/soap-origins/
• Ciftyurek, Muge, and Kasim Ince. "Selahattin Okten Soap Factory in Antakya and an Evaluation on Soap Factory Plan Typology/Antakya'da Bulunan Selahattin Okten Sabunhanesi ve Sabunhane Plan Tipolojisi Uzerine Bir Degerlendirme." Art-Sanat, no. 19, Jan. 2023, pp. 133+. Gale Academic OneFile, dx.doi.org/10.26650/artsanat.2023.19.1106544. Accessed 18 Aug. 2025.
• Costa, Albert B. “Michel-Eugène Chevreul.” Encyclopedia Britannica. https://www.britannica.com/biography/Michel-Eugene-Chevreul
• Curtis, Valerie A. “Dirt, disgust and disease: a natural history of hygiene.” Journal of epidemiology and community health vol. 61,8 (2007): 660-4. doi:10.1136/jech.2007.062380
• Dijkstra, Albert J. “How Chevreul (1786-1889) based his conclusions on his analytical results.” OCL. Vol. 16, No. 1. January-February 2009.
• Gibbs, F.W. “The History and Manufacture of Soap.” Annals of Science. 1939.
• Koeppel, Dan. “The History of Soap.” 4/15/2020. https://www.nytimes.com/wirecutter/blog/history-of-soap/
• List, Gary, and Michael Jackson. “Giants of the Past: The Battle Over Hydrogenation (1903-1920).” https://www.ars.usda.gov/research/publications/publication/?seqNo115=210614
• Maniatis, George C. “Guild Organized Soap Manufacturing Industry in Constantinople: Tenth-Twelfth Centuries.” Byzantion, 2010, Vol. 80 (2010). https://www.jstor.org/stable/44173107
• National Museum of American History. “Bathing (Body Soaps and Cleansers).” https://americanhistory.si.edu/collections/object-groups/health-hygiene-and-beauty/bathing-body-soaps-and-cleansers
• New Mexico Historic Sites. “Making Soap from the Leaves of the Soaptree Yucca.” https://nmhistoricsites.org/assets/files/selden/Virtual%20Classroom_Soaptree%20Yucca%20Soap%20Making.pdf
• “The history of soapmaking.” 8/30/2019. https://www.open.edu/openlearn/history-the-arts/history/history-science-technology-and-medicine/history-science/the-history-soapmaking
• Pliny the Elder. “The Natural History of Pliny. Translated, With Copious Notes and Illustrations.” Vol. 5. John Bostock, translator. https://www.gutenberg.org/files/60688/60688-h/60688-h.htm
• Pointer, Sally. “An Experimental Exploration of the Earliest Soapmaking.” EXARC Journal. 2024/3. 8/22/2024. https://exarc.net/issue-2024-3/at/experimental-exploration-earliest-soapmaking
• Ridner, Judith. “The dirty history of soap.” The Conversation. 5/12/2020. https://theconversation.com/the-dirty-history-of-soap-136434
• Routh, Hirak Behari et al. “Soaps: From the Phoenicians to the 20th Century - A Historical Review.” Clinics in Dermatology. Vol. No. 3. 1996.
• Smith, Cyril Stanley, and John G. Hawthorne. “Mappae Clavicula: A Little Key to the World of Medieval Techniques.” Transactions of the American Philosophical Society, vol. 64, no. 4, 1974, pp. 1–128. JSTOR, https://doi.org/10.2307/1006317. Accessed 18 Aug. 2025.
• Timilsena, Yakindra Prasad et al. “Perspectives on Saponins: Food Functionality and Applications.” International journal of molecular sciences vol. 24,17 13538. 31 Aug. 2023, doi:10.3390/ijms241713538
• “Craftsmanship of Aleppo Ghar soap.” https://ich.unesco.org/en/RL/craftsmanship-of-aleppo-ghar-soap-02132
• “Tradition of Nabulsi soap making in Palestine.” https://ich.unesco.org/en/RL/tradition-of-nabulsi-soap-making-in-palestine-02112
• “Soaps.” https://www.fs.usda.gov/wildflowers/ethnobotany/soaps.shtml
• van Dijk, Kees. “Soap is the onset of civilization.” From Cleanliness and Culture. Kees van Dijk and Jean Gelman Taylor, eds. Brill. 2011. https://www.jstor.org/stable/10.1163/j.ctvbnm4n9.4
• Wei, Huang. “The Sordid, Sudsy Rise of Soap in China.” Sixth Tone. 8/11/2020. https://www.sixthtone.com/news/1006041

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This 2021 episode covers John Dalton, famous for his work in atomic theory. But he wrote one of the first thorough descriptions of what he called “anomalous vision” – he realized he wasn’t perceiving color the same way as other people.

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Holly talks about nebulous passages in the writing of Jane Croly and her brother. Tracy and Holly talk about watching TV as children.

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