Dark Pyrocat HD ?

[mikerz]

I haven't been able to find information about this anywhere -- is dark pyrocat useless? I mixed up about 800ml working solution and only used about half of it, it's now 3-4 weeks later and i was planning on doing another batch, but it's quite dark brown.

Last time I let it sit, I just dumped it to be sure.

[Gem Singer]

Once it is mixed with water to make a working solution, Pyrocat-HD should be used as soon as possible. It oxidizes in a very short time.

The dark working solution was oxidized and useless. You did the proper thing by dumping it.

[Jim MacKenzie]

Agreed. Make up only as much working solution as you need for the film you are about to process. The stock solutions keep a reasonably long time, but the working solutions are only good for an hour or two at most.

[mikerz]

wow! an hour or two at most -- thanks for the advice

[sanking]

wow! an hour or two at most -- thanks for the advice

Pyrocat-HD was designed as a one shot working solution, use and discard. Mix the working solution, develop the film, and discard the used developer. For best results I recommend using the working solution within a 1-2 hour period. You might get away with 3-4 hours, but use a working solution that has been left over night.

Sandy King

[Philippe Grunchec]

BTW, may be it has be discussed somewhere else (but I don't find where...), what is the minimum volume of stock A+B per film (one 135/120, four 4x5", one 8x10")? I'd like to try Semi Stand or even Stand!...
Thanks in advance, sandy.

[sanking]

BTW, may be it has be discussed somewhere else (but I don't find where...), what is the minimum volume of stock A+B per film (one 135/120, four 4x5", one 8x10")? I'd like to try Semi Stand or even Stand!...
Thanks in advance, sandy.

For minimal type agitation you must first determine how you are going to develop the film, i.e. in a tube, in a tray or in some type of tank. When you make this decision the minimum amount of solution is what fills the container and covers the film.

Do tubes, trays or tanks work better with minimal agitation? Well, people have gotten good results using all three but I personally prefer methods that keep the film standing in the vertical position. I develop sheet film in tubes, standing on end, and medium format feel on stainless steel reels in stainless steel tanks. This works for me but I am not saying these are the only methods that work.

Sandy King

[Philippe Grunchec]

Sandy, I did not mean the amount of working solution, but the amount of A+B stock: 3+3ml, 5+5ml?

[IanG]

Ilford did quite a lot of work on the actual amount of developing agents used in processing a film in the mid 1950's

In theory approx 0.5 gm. of hydroquinone/pyrocatechin (or 1.6 gm. of metol or 0.25 gm. phenidone) are used up in reducing 1.74 gm. of silver bromide to produce 1 gm. of silver. That's approx 12 rolls of 120 film with average exposures & development.

However a litre of developer containing 0.5 gm. of hydroquinone/pyrocatechin will not develop this area of exposed negative properly. As the concentration of developing agent falls the concentration of by-products increases, development slows down and the characteristics of the developer would be very different from the fresh solution.

A litre of Pyrocat HD at 1+1+100 contains approx 0.2 gm Phenidone & 0.49 gm Pyrocatechin.

In my own case I process 2 roll of 120 per litre, or 6 5x4's (equivalent to 1.5 rolls), if I were to change that to 4 rolls per litre there would be a slight difference easily adjusted by increasing the dev time marginally.

If that's taken a step further to 4 rolls in a litre at 1+1+200 dilution then there would be significant fall off in developer activity leading to a reduction in D-max and a marked compression of tones, usually called compensation, however processing 4 roll in a larger volume say 2 litres of 1+1+200 Pyrocat will help negate this compression and loss of high light detail.

So your question is a good one, there's a balance of dilution & volume which can have a very great effect on the resulting negatives. The importance is having sufficient excess of developing agents.

Ian

[sanking]

Sandy, I did not mean the amount of working solution, but the amount of A+B stock: 3+3ml, 5+5ml?

Sorry for the misunderstanding.

For stand or semi-stand agitation I would suggest a slightly asymmetric mixture re: A and B of 1.5 parts A + 1.0 parts B + 200 parts water. This helps to reduce oxidation that sometimes comes with long development times and high speed films like TMY. You will be using a fairly large total amount of working solution so the developer should not totally exhaust, even with long development time of over an hour.

Sandy