510-Pyro is one of the new generation of staining and tanning developers, and said to give similar results as Pyrocat or PMK. It was formulated by Jay DeFehr in the USA and arrived on the scene with claims of very fine grain, high acutance, good stain, and extreme longevity. We’ve heard these before right? However, as the developer became more widely used, and people started testing it for themselves, a following took shape with photographers reporting good results with both normal development, stand and semi-stand techniques.

It is remarkable that the developer is used at dilutions from 1+100 or 1+200 for normal development, and up to 1+500 for stand development.

Some benefits

The developer uses Pyrogallol, the second oldest developing agent ever used (after gallic acid). It became very popular in the late 19th century until displaced by the ubiquitous Metol. However, pyrogallol has two main advantages over metol. These are:

1. An oxidisation stain created by Pyro, which becomes a natural filter to tame highlights and ease printing, especially with graded papers.

2. Tanning or hardening of the gelatine emulsion which both protects the negative from damage and reduces developer movement through the emulsion creating higher beneficial acutance in the image.

These two benefits are enormous when done right; and the hunt for a way to use Pyro has continued for over a century. 510-Pyro claims to have achieved not only these two benefits, but also the Holy Grail of photography, ultra fine grain with high sharpness. I want to add yet another additional benefit for me, a single solution stock (no mixing of A, B) that keeps for years.