Sodium Hydroxide…

…also known as caustic soda, lye, and believe it or not, drain cleaner.

It’s probably the ingredient of most concern amongst people who don’t understand the role of sodium hydroxide in soap making. Handled correctly, lye is not to be feared, despite the fact that is highly corrosive. Do you remember that scene in the 1999 movie Fight Club, where Tyler Durton (Brad Pitt) uses lye to burn the hand of The Narrator (Edward Norton)? That wasn’t exaggerated - lye burns can absolutely be that nasty! Thankfully, I’ve never given myself one, which is a miracle given how clumsy I can be!

Although sodium hydroxide in the form of caustic soda is brilliant for unblocking clogged drains, it’s also the magic ingredient in soap making. When lye is mixed in the right proportions with fats, it undergoes a chemical reaction known as saponification - converting esters (fats) into salts of fatty acids - resulting in soap. Who knew that soap is basically a salt? Once saponification is complete, if the soap maker has measured everything correctly, there is no sodium hydroxide left…just soap, which is perfectly safe to use!

But sodium hydroxide is used for more than just cleaning drains and making soap. It has many applications across a variety of industries. It’s used in the manufacture of paper (soda pulping), in water treatment plants to regulate PH, and is a common tool in the food production industry. Classified by the FDA as “generally recognised as safe”, it’s regularly used to cure olives, to remove the skins of fruit and vegetables before canning, and to treat pretzel dough and bagels, giving them that distinctive shiny finish.

All in all, sodium hydroxide is not the monster some people believe it is. Yes, it can be harmful, and yes, it should absolutely be treated with respect and caution, but no…it’s doesn’t need to be avoided like the plague. Sodium hydroxide is definitely friend, not foe!