Moersch Pyro 48 is a two-part pyrogallol developer for black and white film: 100 ml of part A and 200 ml of part B.
What it is for
Pyro developers stand apart from all the rest: alongside the silver image they build a dye stain in the gelatin itself, proportional to density. That stain acts as a built-in masking filter — it holds the highlights back, so skies do not blow out and highlight detail survives where an ordinary developer has already lost it. That is precisely what printers value in these negatives.
How to dilute it
From 100 ml of part A and 200 ml of part B you get up to 40 films.
It is a one-shot developer: mix the working solution, use it, discard it. That is the most predictable way to work — every film is developed in fresh solution, so times need no extending from roll to roll.
The single most important thing about this developer: once mixed it lives about an hour. Prepare it immediately before development and only as much as you need — there is no keeping it until tomorrow.
Storage
Sealed concentrate keeps well but dislikes air: the emptier the bottle, the faster it oxidises. Decant the remainder into a smaller bottle, or displace the air — that is what gets a concentrate to its last measure.
How it compares
The genre's classics are Pyrocat-HD and Tanol; Pyro 48 belongs beside them. Against any ordinary developer the difference is not grain but how the highlights behave: pyro gives the headroom that rescues a subject at the enlarger.
