Pyro devs, and Stop & Fix

[Ian Grant]

Pyrocat HD can be used with an acid Stop bath - at half strength, and a typical fixer like Hypam, or Ilford / Kodak Rapid fixer, they have no effect on the staining.

One chemist on Photrio checked the stain density differences using a water stop and an acid stop bath with PMKl some years ago, he found a 0.1 higher density with water, and concluded that it was likely to be because development carries on longer with a water stop/rinse, compared to an acid stop bath. It's also likely there's some dichroic fog with a water rinse and an alkali fixer, which would be similar in colour to the Pyrogallol stain.

Ron Mowrey/PE on Photrio, who devised some of the Alkali fixers like TF-2, TF-3 and TF-4, stated that you always needed to use an acid stop bath with an alkali fixer as he saw dichroic fog in early tests. Essentially with a water rinse the alkali in the fixer causes residual developer in the emulsion to begin working as the film is fixing, before it clears.

My experience with Pyrocat HD of 17 years plus, is also as an alternative Pyrocatechin re-developer for Ilford IT-8 toner, something I’ve used a few times over the years, amazing Olive black tones unlike other toners, I must have first used it in the very late 1970s, but the simple Pyrocatechin redeveloper has a very short tray life, Pyrocat HD works just as well and gives the same tones, lasts a bit longer.

My point though here is after trying water stop, and acid stop bath, acid fix and alkali fix, no-one of these affect the stain which is very stable.

We have to take inexperienced peoples comments with a piece of salt, users or sellers.

A chemist, to PhD level:

The stain caused by pyrogallol, catechol, and hydroquinone consists of oxidation products (polyphenols) of the developing agent. These are lumped together under the term humic acids. The stain is dark coloured and insoluble in water. I doubt whether the stain once formed can be bleached by the bisulphite ion in the fixer. The stain that forms in developer trays is the same substance, and it is very difficult to remove, requiring a strong dichromate bleach.

Ian

 

[Ian-Barber]

So are you saying here that a normal water bath for PyroCat-HD is perfectly ok to use wihouth causing any issues

 

[thronobulax]

I have used a running water stop bath with a fairly high flow rate, along with TF-4 fixing for years with all film development and all developers, Pyro-based or otherwise and gotten consistently good results.

 

[Ian Grant]

So are you saying here that a normal water bath for PyroCat-HD is perfectly ok to use wihouth causing any issues

As long as you are using a normal fixer like Hypam or Ilford.Kodak Rapid fixer yes, they have a pH of around 5.2 to 5.4 which are very mildly acidic and.

I have used a running water stop bath with a fairly high flow rate, along with TF-4 fixing for years with all film development and all developers, Pyro-based or otherwise and gotten consistently good results.

Consistently good results is not in the same league as consistently excellent results. There are a lot of myths about staining developers, the worst was from Gordon Hutchings, the recommendation that after fixing and a short rinse you re-immersed your PMK negatives in the spent developer as that increased the stain, sure it does, but it increases base stain so is in fact detrimental.

Ian.

 

[Ian-Barber]

As long as you are using a normal fixer like Hypam or Ilford.Kodak Rapid fixer yes, they have a pH of around 5.2 to 5.4 which are very mildly acidic and.

I have been using Fotospeed FX30 Odourless Fixer but will need to order more fixer very soon

 

[Ian Grant]

The Dichroic fog issue really only surfaces noticeably when fixers are partially used, and increases towards their capacity. So as long as fixer is fresh, and clearing times are short, it's unlikely to be a problem.

Fotospeed's Odourless fixer is pH 6.5, so it's just marginally on the acidic side of neutral.

Ian

 

[thronobulax]

Consistently good results is not in the same league as consistently excellent results. There are a lot of myths about staining developers, the worst was from Gordon Hutchings, the recommendation that after fixing and a short rinse you re-immersed your PMK negatives in the spent developer as that increased the stain, sure it does, but it increases base stain so is in fact detrimental.

Ian.

Which - as I recall - he retracted once he had further experience with the process. New things take time to master and tune, and PMK was no different. In the mean time many of us - myself included - got wonderous negatives even with the redipping originally recommended. It certainly doesn't seem to be a lack of competence on his part (which your tone might suggest).

More to the point, the work we do isn't laboratory sensiometry. It's purpose is to make prints (or scans) we love. Within reasonable limits, repeatability is far more important than absolute precision. It makes essentially no difference whether you fix in running water or acid stop so long as whatever you do, you do consistently. My only reason for choosing running water stop is historic. I wanted to avoid any risk of negative pinholing that plagued some older emulsions when they moved from an alkaline developer to acidic fixer. These days, that's no longer an issue, but having created a repeatable and consistent practice in my darkroom decades ago, I see no particular reason to change.

 

[David M]

It’s a non-photographic issue, so I apologise in advance, but recent events mean that all of us, including photographers, should be curbing our addiction to freely running water.