Saponification
An alkali reacting with a fat to make soap. It is how soap is manufactured, and it is also how oven cleaner removes baked-on grease.
In detail
A strong alkali reacts with a fat or oil and converts it chemically into soap and glycerol. That reaction is how soap has been made for millennia, and it is also, unexpectedly, how the harshest cleaning products work. Oven cleaner, caustic degreasers and the alkaline family of drain products do not dissolve baked-on fat or a fatty blockage — they convert it into something water-soluble, which then rinses away. Understanding it as a chemical conversion rather than as strong cleaning explains three things at once. It explains why these products work where a detergent has failed, since a detergent only emulsifies what is already there. It explains why they are hazardous to skin: skin is largely lipid and protein, and the same reaction runs on contact, which is why an alkali burn feels soapy and progresses without much pain at first. And it explains their material limits — an alkali strong enough to saponify fat also attacks aluminium, zinc and galvanised steel, releasing hydrogen, and damages paint, some plastics and rubber. Saponification is also the other half of the soap-scum story, since soap made this way precipitates in hard water.
Why
- Potassium hydroxide is explained by Saponification
- Soap is explained by Saponification
- Oven cleaner is explained by Saponification
- Drain cleaner is explained by Saponification
- Oiled wood is explained by Saponification
- Sugar soap is explained by Saponification
Sources for this page
Sources
Right to Know Hazardous Substance Fact Sheet: Potassium Hydroxide (RTK 1571)
New Jersey Department of Health, 2010 · Government or regulator
Relied on for: That potassium hydroxide is used in making soap, that it is highly corrosive to skin and eyes, and that it is corrosive in moist air to aluminium, zinc, tin and lead. (states this directly)
What's in drain cleaner and what happens if you drink it?
National Capital Poison Center (Poison Control) · Poison or chemical-safety authority
Relied on for: That non-enzymatic drain cleaners are strong acids or strong alkalis and that some generate heat, which is part of how they act on grease and fat. (states this directly)