Lye (also known as Caustic soda)'s a corrosive alkaline substance, commonly, sodium hydroxide (NaOH). Previously, lye was among the many different alkalis leached from hardwood ashes. Now, lye's commercially manufactured using a membrane cell method, which's an improvement from the previous diaphragm cell methods of Castner-Kellner, Gibbs, and Nelson. Solid dry lye's commonly available as flakes, pellets, microbeads, and coarse powder. It's also available as solution, often dissolved in water.… (More on Lye)