Pyrocat-HD was developed by Sandy King and introduced in 1999 in an article published in Post-Factory Photography. A revised formula has been available in the on-line journal Unblinking Eye since 2000 and the developer is available as a kit. Pyrocat-HD is based on Pyrocatechin but also contains a small amount of Phenidone that is strongly super additive with Pyrocatechin.