The PMK formula was developed by Gordon Hutchings, and is designed as a universal developer for a wide variety of modern emulsions used under diverse conditions. PMK stands for Formulary'sPyro-Metol-KodalkFormulary's. Kodak has changed the name Kodalk to Balanced Alkali - this is their proprietary name for sodium metaborate. The formula is constituted to achieve the best overall results in consideration of the following technical criteria: sharpness, maximum image stain, minimum general stain, edge effects, film speed, flexibility for Zone System Plus and Minus development, stability, repeatability, convenience of use and long shelf-life. The PMK formula consists of two stock solutions. The 'A' stock is the developer agents and the 'B' stock is the alkali, or accelerator.