is lye a soap ingredient
...but also (technically) no, because all bar soap must be made with lye. It is necessary for the integral chemical process that changes fat into soap. I won't get into the details of that reaction because that is not what you are asking, but suffice it to say that lye is a required ingredient when making solid soap.
See Reviews | Review this Product. Sodium Hydroxide (Lye) - for Soap Making. Sodium Hydroxide, or Lye, is the chemical that induces saponification with fats and oils to create that magnificent thing called soap! This lye is in flake form and is easier to measure without worrying about static cling.