Everything Everywhere Daily: A History of Soap and Detergent

Host: Gary Arndt
Date: September 26, 2025

Episode Overview

In this episode, Gary Arndt dives into the fascinating history and science behind two everyday cleaning essentials: soap and detergent. He traces their accidental origins, technological innovations, and impact on society, breaking down the chemistry that makes them work and highlighting key turning points—from ancient Babylonia to modern shampoos. The episode also contrasts soap and detergent, explains their environmental impacts, and offers insight into why we use each today.

Key Discussion Points & Insights

1. The Ancient Origins of Soap

• Early Discovery:

  • Soap was probably discovered by accident thousands of years ago when animal fat mixed with wood ash and water produced a soap-like substance.
  • The oldest archeological evidence is from Babylon, circa 2800 B.C., where fat and ash mixtures were found in clay cylinders.
  • Quote:

    "It probably happened when melted animal fat was mixed with wood ash from a campfire and then mixed with water." (04:30)

• Ancient Uses:

  • Early soap-like mixtures were not for personal hygiene but used in cleaning textiles, especially wool and cotton.
  • Ancient Egypt (1500 BC): Used animal/vegetable oils with alkaline salts for cleaning, connecting cleanliness to both health and religious purity.

• Roman Contribution:

  • The Romans developed "sapo," the etymological root of "soap."
  • The Mount Sapo legend illustrates the accidental creation of soap through sacrificial animal fat and wood ash.

2. The Chemistry of Soap

• Saponification:

  • Early civilizations unknowingly performed saponification, the chemical reaction where fats combine with strong alkalis to form soap.

    • Alkali: Sourced from potassium, sodium, or calcium hydroxide in wood ash.

  • Soap Molecules:

    • Composed of a hydrophilic (water-loving) end and a hydrophobic (water-hating) end.
    • These latch onto grease and dirt, forming micelles that trap the contaminants, making them easy to rinse away.

  • Quote:

    "One end of the soap molecule loves water, which is called hydrophilic, while the other end hates water and is called hydrophobic." (07:25)

  • Soap lowers water's surface tension, enabling it to better penetrate fabrics and skin, making cleaning more effective than water alone.

3. Medieval and Early Modern Innovations

• Islamic World:

  • Cities like Aleppo and Damascus became major soap centers, perfecting hard olive oil-based soaps (e.g., Aleppo soap).

• Europe:

  • Soap making guilds in France, Italy, and Spain produced export-worthy soaps like Marseille soap.

• Luxury Status:

  • Despite advances, soap remained a luxury; the majority relied on sand, ash, or water for cleaning.

• Quote:

  "Medieval soap makers... refined techniques, experimented with different oil combinations, and developed better methods for controlling the saponification process." (12:10)

4. The Industrial Revolution: Soap Becomes Ubiquitous

• Mass Production:

  • Mechanization, especially by companies like Procter & Gamble (1837) and Lever Brothers (1885), made soap widely available.

• Key Innovations:

  • Nicolas Leblanc (1791): Created an affordable method to produce soda ash (alkali) from salt.
  • Michel Chevreul (1823): Deciphered saponification, allowing controlled, precise soap manufacturing.

• Consumer Gimmick:

  • The famous "floating" Ivory Soap was created by accidental over-whipping, which added air to the batch.

  • Quote:

    "According to legend, the floating nature of Ivory soap was discovered by accident... it was lighter and could float in water." (16:20)

5. The Limitation: Soap Scum & Hard Water

• Chemical Issue:
  • Hard water, rich in magnesium and calcium ions, neutralizes soap’s cleaning ability, causing soap scum.
  • Traditional Fix:
    • Use of washing soda (sodium carbonate) to soften water and enable effective soap use.

6. The Rise of Detergents

• Origin:

  • Developed in Germany during World War I due to fat shortages.
    • Used petroleum and coal-tar derivatives as the base.
  • Breakthrough in the 1930s: Procter & Gamble creates the first synthetic household detergents.

• Key Differences from Soap:

  • Structurally similar (with hydrophilic and hydrophobic ends, forms micelles).
  • Do not interact with magnesium/calcium in hard water, thus prevent soap scum.
  • Can be formulated for specialized cleaning tasks and were effective in cold water.

• Quote:

  "Detergents, unlike soap, don't produce soap scum and leave a residue behind." (19:10)

7. Environmental Impact: The Phosphates Problem

• 1940s–50s: Detergents were supercharged with phosphates (builders) for better cleaning in hard water.
• Environmental Consequences:
  • Runoff led to eutrophication: overgrowth of algae in lakes/rivers, disrupting ecosystems ("Lake Erie declared dead").
• Modern Response:

  • Most consumer detergents are now phosphate-free due to these environmental impacts.

  • Quote:

    "These excess nutrients fueled the explosive growth of algae in lakes and rivers... When algae died and decomposed, the process consumed dissolved oxygen in the water, suffocating fish or other aquatic life." (21:55)

8. Shampoo: A Special Case

• Etymology:
  • "Shampoo" originates from India, originally as an herbal hair application.
• Historical Practices:
  • Hair was washed with bar soap, but left residues and buildup in hard water.
• Modern Shampoo:

  • 1930s: US introduction of the first widely effective liquid shampoo (Drene by Procter & Gamble), which used detergents rather than soap.

  • Today's shampoos use a range of detergent-based surfactants, adapted for different hair types and water conditions.

  • Quote:

    "The first widely marketed liquid shampoo in the US was Drene... it was a detergent, not a soap." (24:45)

9. Soap vs. Detergent: Accessibility and Scale

• Soap Making:
  • Remains a simple, artisanal process available to hobbyists and small markets.
• Detergent Production:
  • Requires complex, industrial processes and is not easily replicated at home.

10. The Universal Challenge

• Despite thousands of years, the fundamental challenge—removing oily dirt with water—remains largely unchanged.
• Our solutions, however, have become much more sophisticated and better tailored to the needs of modern life.

Notable Quotes & Memorable Moments

• On Early Soap Discovery:

  "It probably happened when melted animal fat was mixed with wood ash from a campfire and then mixed with water." (04:30)

• On Soap Chemistry:

  "One end of the soap molecule loves water, which is called hydrophilic, while the other end hates water and is called hydrophobic." (07:25)

• On Medieval Soap Making:

  "Medieval soap makers... refined techniques, experimented with different oil combinations, and developed better methods for controlling the saponification process." (12:10)

• On Ivory Soap's Floating Feature:

  "According to legend, the floating nature of Ivory soap was discovered by accident... it was lighter and could float in water." (16:20)

• On Detergents and Hard Water:

  "Detergents, unlike soap, don't produce soap scum and leave a residue behind." (19:10)

• On Phosphates & Water Pollution:

  "These excess nutrients fueled the explosive growth of algae in lakes and rivers... When algae died and decomposed, the process consumed dissolved oxygen in the water, suffocating fish or other aquatic life." (21:55)

• On the Modern Shampoo:

  "The first widely marketed liquid shampoo in the US was Drene... it was a detergent, not a soap." (24:45)

Timestamps for Key Segments

• 00:50 – Introduction to soap's origins
• 03:45 – Early archeological evidence (Babylon, Egypt)
• 06:30 – Chemistry of soap & saponification
• 10:21 – Medieval soap innovations (Aleppo, Europe)
• 12:45 – Mass production & industrialization
• 15:10 – The Ivory soap accident
• 17:00 – Hard water and the problem of soap scum
• 18:40 – Invention of synthetic detergents
• 21:40 – The phosphate issue and environmental impact
• 23:45 – The rise of modern shampoo
• 26:00 – Legacy: soap and detergent today

Final Thoughts

Gary highlights the remarkable journey from primitive cleaning agents to technologically advanced products that underpin our hygiene and health. The episode is packed with historical anecdotes, clear scientific explanations, and social context, making it accessible for anyone curious about the everyday essentials that keep our world clean.