Pyrocat-MC is a new staining B&W developer, formulated by Pat Gainer and Sandy King and based on Sandy’s Pyrocat-HD, that is made up as a stock solution in propylene glycol. (Staining developers are those which cause the gelatin that supports the emulsion to be “tanned” by the by-products of the development process. This stains the film in proportion to the extent of development that has taken place in a particular area — you get a silver image and a stain image. The stain itself is orange or yellow in colour and is somewhat opaque to the light used for making prints, which has the effect of smoothing out grain during printing. In addition, the stain is often very opaque to UV light, making stained negs very useful for printing in platinum or other iron-based processes, which are sensitive to UV.)
Pyrocat-MC is mixed as a stock solution (part A) in propylene glycol. The stock solution is mixed with an activator (part B) and diluted in water just before use.
The formula of Pyrocat-MC Part A is given by Pat Gainer as the following:
2.5 g metol
4.0 g ascorbic acid
7 ml triethanolamine
Mix with about a few ml of water until a thin slurry is formed, then add
100 ml warm propylene glycol
50 g catechol
Keep the solution warm and stir until the catechol dissolves, then make up to 1 L with propylene glycol.
The activator (Part B) is traditionally a solution of 750 g potassium carbonate in 1 L of water. The working solution is then formulated as 1+1+100 (Part A:Part B:water). However, I used the sodium carbonate activator, 200 g sodium carbonate in 1000 ml water. The working solution is then formulated as a 1+5+94 mixture.
Sandy King’s article describing Pyrocat-HD (the original developer) is hosted at at UnblinkingEye.com. The original description of the Pyrocat-MC version is at this APUG.org thread. The information sheet from the Photographer’s Formulary (who sell a pre-made Pyrocat-MC kit) can be found in this PDF file.
My Pyrocat-MC experiences are described elsewhere on this site.