Lye is a corrosive alkaline substance, commonly sodium hydroxide (NaOH, also known as caustic soda) or historically potassium hydroxide (KOH, from hydrated potash). Previously, lye was among the many different alkalis leached from hardwood ashes. Now, lye is commercially manufactured using a membrane cell method.
Solid dry lye is commonly available as flakes, pellets, microbeads, and coarse powder. It is also available as solution, often dissolved in water. Lye is valued for its use in food preparation, soap making, biodiesel production, and household uses, such as oven cleaner and drain opener.
Lye is often used as electrolyte for hho cells and is considered to be the best electrolyte because it's small reaction with stainless steel electrodes. (316L being the best steel for electrodes)