Ethylenediamine pyrocatechol (EDP), also known as ethylenediamine-pyrocatechol-water (EPW), is an anisotropic etchant solution for silicon.^[1] A typical formulation consists of ethylenediamine, pyrocatechol, pyrazine and water. It is carcinogenic and very corrosive.^[1] It is mainly used in research labs, and is not used in mainstream semiconductor fabrication processes.^[1]