Caustic soda is sodium hydroxide which is lye – they are the exact same thing; just different names. The reason behind the different names is mainly to do with the chemical name being “sodium hydrate” and the chemical itself is “caustic or corrosive”, leading to being known as caustic soda.

Caustic soda is sodium hydroxide which is lye – they are the exact same thing; just different names. The reason behind the different names is mainly to do with the chemical name being “sodium hydrate” and the chemical itself is “caustic or corrosive”, leading to being known as caustic soda.