NemoClaw Knowledge Wiki

Waterproofing Fabrics with Soap and Alum: History, Chemistry, and Limitations

4 min read

Waterproofing Fabrics with Soap and Alum: History, Chemistry, and Limitations

Generated: 2026-06-08 · API: Gemini 2.5 Flash · Modes: Summary

Waterproofing Fabrics with Soap and Alum: History, Chemistry, and Limitations

Clip title: Waterproof Fabric with Soap. Forgotten knowledge that was once used as a scam Author / channel: NightHawkInLight URL: https://www.youtube.com/watch?v=7Sc1rjGMblM

Summary

The video explores the history, chemistry, and practical application of “metal soap,” specifically aluminum stearate, as a waterproofing agent for fabrics. The host begins with a captivating demonstration of a holed fabric surprisingly holding water, introducing this “200-year-old chemistry scam.” He recounts the accidental discovery in the early 1800s: a fabric manufacturer’s unrinsed, soap-laden cloth became water-repellent after being soaked in an alum (aluminum sulfate) bath intended for dyeing. This serendipitous reaction formed insoluble aluminum soap, a novel waterproofing technology.

The host delves into the chemistry, explaining that traditional soap (sodium stearate) is produced by reacting animal fat or oil (containing stearic acid) with lye (sodium hydroxide). Sodium stearate is water-soluble, but when it encounters a metal salt like alum, a chemical exchange occurs, forming aluminum stearate and sodium sulfate. Aluminum stearate, unlike its sodium counterpart, is not water-soluble, thus creating the waterproofing effect. The video also highlights that other metal salts like Epsom salt, zinc sulfate, iron sulfate, or calcium chloride can be used to create similar metal stearate coatings.

Initially, the presenter demonstrates the apparent success of this method with gentle water application. However, a crucial caveat emerges when water is applied with greater force, such as from a spray bottle, causing the waterproofing to fail. Referencing a 1930s book, “Waterproofing Textile Fabrics,” the host reveals that this “ancient process” was largely deemed impractical for general textiles. The book states that achieving adequate water resistance required such a high concentration of metal stearate that it compromised the fabric’s properties, making it rough and unsuitable for clothing, and that simple wax coatings offered superior results. The “mosquito netting demonstration” (gentle water pouring) was even described as a misleading technique used to impress investors.

Despite the initial disillusionment, the host explores a different 1930s text, “The Waterproofing of Fabrics,” which focuses on heavy cloths like sailcloth. This book outlines a more rigorous two-step process: soaking the fabric first in a soap solution, wringing it out, and then soaking it in a metal salt solution (like zinc sulfate or alum). This method allows the insoluble metal stearate to form within and upon the fibers. The host then demonstrates this refined two-bucket technique, emphasizing the importance of wringing out excess soap before the second bath and even suggests applying heat with an iron for increased durability. The updated results show significant water repellency, with minimal penetration even under sustained water exposure. While admitting that wax might still offer superior waterproofing, the host concludes that this refined metal stearate method provides a durable and surprisingly comfortable coating, especially for certain applications, suggesting it’s an “abandoned idea” that warrants further investigation.

Video Description & Links

Description

Ad: Check out my sponsor and remove your personal information from the web at https://JoinDeleteMe.com/nighthawk and use code NIGHTHAWK for 20% off. DeleteMe international Plans: https://international.joindeleteme.com

In this video we explore the history of soap waterproofing methods, using sodium stearate to form hydrophobic coatings with a variety of metal salts. Linked below are the books referenced in this video:

Waterproofing Textile Fabrics: https://play.google.com/books/reader?id=fghLAAAAMAAJ&pg=GBS.PA40&hl=en

The Waterproofing of Fabrics: https://www.google.com/books/edition/The_Waterproofing_of_Fabrics/UrhLAAAAIAAJ?hl=en&gbpv=1

The Development of the Incandescent Electric Lamp: https://play.google.com/books/reader?id=kJQ3AAAAMAAJ&pg=GBS.PP1&hl=en

A special thank you to my top patrons: Aik193, Aleksander, bandit, Bartholomew Spawndoom, Boatyard McBoatface, Brad Alan Armstrong, Brian, Brian Bowles, Bryan Shattuck, Carl Katzenberger, Chris, Christopher Calkins, Christian, Connor Davis, Daniel Bauman, Dan L, Daniel Moore, David Burburan, Dean Maurer, Dustin B, Edward Ivory, Edward Unthank, Eugene Pakhomov, Enzo Breda Lee, Etalon, Evan Hughes, Evan Relf, GadgetPatch, GEOCAHEPUNA, Gusbear, Henner Zeller, Isaac Wiebe, Jedediah Kivi, Jeremy, Jon Hartmann, Johnathon Otte, Jonathan Wilt, Josh Hoppes, Julian Meßmer, JWC, Keith Tucker, Kejie YU, Kris Pockell, Lisa L, Manuel Barkhau, M W, Mark Roth, Martha Williams, Matthias S., Merrill Crawford, Michel Pastor, Moopy (Mike), Oliver, OscarCorx, overra, PabloXIII, Parker Jones, Peter Gordon, PeteyPak, PFC_CMC, RPMatthew, Ryan Shoaf, Sam Hodge, Santiago Perez, Scott Schlesier, Shadow VanDusen, Simone Chiesi, Steve C, Syniurge, Ted Brandston, The Coldrays Team, Trance Maharaj, TWSBI, UltimApe, Walter Montalvo, White Hat, Y@, Yanko Yankulov, Alvaro Figueroa

https://www.patreon.com/c/NightHawkProjects

Thank you for watching!

URLs

Graph View

Backlinks