PMK Pyro : LUSENET : B&W Photo - Film & Processing : One Thread

I hope this isn't a stupid question......

If I understand the Pyro process correctly, the stain is produced by the oxidation products of pyrogallol, principally purpurogallin. Would it therefore be possible to develop a film in a different developer, say Rodinal, and then immerse the fixed film into an oxidised bath of pyro, in order to get a similar staining effect? (I am not sure if a latent stain is produced by the pyro during development, which is then induced by the post-fixing alkaline bath, which would preclude this). However, if it as possible to stain after development in a non-pyro developer, the overall process might be easier (and possibly safer), and you might be able to combine the acutance and compensating effect of a developer such as dilute Rodinal with the highlight separation effects of pyro. Any thoughts?

-- fw (, April 24, 2000


Interesting idea. I don't think it would work. The after-bath that induces the stain is simply an alkaline solution (sometimes the spent developer is used, but a teaspoon of Kodalk in a quart of water does the same thing). I believe it is the tanning action of pyro on the film emulsion, in combination with an alkaline environment, that is the key to the stain. No tanning action, no stain.

-- Ed Buffaloe (, April 25, 2000.

As far as I understand pyro, the stain should be related to the exposure, so at the development stage silver is reduced and pyrogallol oxidised at a certain ratio and immobilised in the emulsion. So using a after bath the reduced silver will not react in the same way with oxidised pyrogallol.

I'm using PMK with water stop and tetenal smell free rapid fixer (pH around 6) and do get the stain on Forte 400 straight, which means no after bath is required (stain does not change in 1% Carbonat solution).

Without chemical reaction at the development stage probably no stain.



-- Wolfram Kollig (, April 27, 2000.

Wolfram's right, the stain has be proportional to the density of the silver image, otherwise what's the point?

You can use a re-halogenating bleach, such as is used in certain intensifying processes, and then re-develop in Pyro to get the staining effect, but you would probably lose most of the characteristic of the original developer. The Pyro stain tends to spread out in the emulsion, so I don't think a true acutance effect is possible.

-- Pete Andrews (, April 27, 2000.

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