Hypercat developer by Jay De Fehr

Some times ago I was involved in some test with the Hypercat developer, great one, by Jay De Fehr. 

Here a forum about this one: Hypercat acutance developer

Using the Jay words:

Hypercat, a catechol-based tanning/staining developer with very special properties.

Initially I spent a lot of time to well understand all the terms of the question. Hypercat uses proportional stain, that is the amount of the colored stain is proportional to the light received by the film during the exposure. Not all the stain developers have the same properties, many of them are not proportional that is leave a sort of fog.

Cathecol is a friendly name for pyrocatechol and during the development leave a brown stain, caused by the oxidation of the developer. It works replacing the gapes between silver compounds in the film emulsion. In the traditional films it works very well, but in some cases, with tubular grain films the gapes between silver crystals are too much small and it doesn't work at all (i.e. Kodak T-MAX 100 do not works at all, but in Kodak T-MAX 400 it works very well).

The recipe is made by two parts, a developer agent in the part A and an alkaline agent in the part B; concentrations of both parts may be adjust for special purpose.

The classical recipe:

Stock Solution A

ascorbic acid 1g
catechol 10g
propylene glycol 100ml

Stock Solution B

distilled water 750 ml
sodium carbonate 200g
distilled water to 1 liter

A sheet that is useful for understand basic developing times:
DigitalTruth Hypercat

Looking at the film under a side light, at the end of the development, you can see as a height effect in the high density and the total absence of emulsion in the blacks; a strange effect very different from all other "standard" developers.

Under the enlarger the brown stain keeps the high lights under control, even if you use the contrast filter grade 5; this is a lot useful in some high contrasted scenes hard to render under the enlarger. On the other side you have to use only multigrade papers. You can use even a multigrade paper without a filter (usually give a grade 2 if your lamp is a darkroom dedicated lamp) with nice results. Blacks are often "deep blacks" in the sense that without the emulsion the classic "fog+base" density becomes almost near to "base" only, a stunning effect.

I made two times the recipe for the part B of the formula: the first time I used Soda Solvay for the sodium carbonate, but some micro dusts in the film appears; the second time I replace the part B with potassium carbonate (in a different proportion because potassium carbonate is weaker base respect to potassium carbonate) and all works fine. Anyway the problem wasn't the sodium carbonate by itself but the purity grade of the chemical... :-)! Jay wrote this post for explain more the mix ratio that we have to use in the stock: Mix ratios 

Jay helps me a lot of times during the initial set up phase and test, give me always the right direction for solve some problems (caused all them by my initial inexperience).

Hereafter three sets of the initial setup phase made with a medium speed film, Rollei RPX 100 (exp @80 ISO).

Sodium carbonate, wrong test (120 film, micro bubbles, normal and low contrast scene)

Sodium carbonate, first success (120 film, normal contrast scene)

Sodium carbonate, last test (120 film, normal contrast scene)

Potassium carbonate, success test 35mm (Kentemere 100 film)

Other examples (Kodak TRI-X 400 35mm Hypercat standard with potassium carbonate part B):
https://www.flickr.com/photos/padesig/11711345736/
https://www.flickr.com/photos/padesig/11711927986/
https://www.flickr.com/photos/padesig/11709908415/

Even if the film seems sometimes very thin, the stain assure always great results, both in scanning and under the enlarger. Really a surprise for me. Just in the yesterday evening darkroom session (31/05/2016) I have had great results even with lith prints....!

Hypercat is a great developer with high acutance. Jay suggest to use minimal agitation rates (initial agitation of 45 seconds that one every 3 minutes) or geometric agitation (initial agitation of 45 seconds than at minutes 1, 2, 4, 8, 16, 32). Geometric agitation is a way to obtain good shadows develop and good compensate effect on the high lights.