Anybody using Pyrocat-HD or MC as a Compensating Developer?

[Ken Lee]

Patrick
Sinar P, 300mm Fujinon A
5x7 HP5+, Divided Pyrocat HD

To render the scene inside the room, a 6-second exposure at f/16 was required. The darkest values on the jet-black dog, were actually too low for my light meter to measure. The scene outside the window - bright sunshine on foliage - fell on Zone 14.

[Jay DeFehr]

[QUOTE=sanking;587090]Andrew,

Think of the specific functions of both baths.

In Solution A the emulsion soaks up the reducer. How much it can absorb is determined by temperature (at higher temperatures the gelatin swells more, allowing more reducer to be absorbed) and agitation (more agitation also means more reducer being absorbed. However, there is a limit to how much reducer the gelatin will absorb, and that limit is usually reached at about five minutes at 75-80 degrees with constant agitation. However, five minutes at 75 degrees with intermittent agitation gets you to about 95% of the maximum so that is where I usually work.QUOTE)

Sandy,

How does agitation increase absorption? How do you measure absorption? What is the goal in maximizing absorption?

[Jay Decker]

... Think of the specific functions of both baths.

In Solution A the emulsion soaks up the reducer. How much it can absorb is determined by temperature (at higher temperatures the gelatin swells more, allowing more reducer to be absorbed) and agitation (more agitation also means more reducer being absorbed. However, there is a limit to how much reducer the gelatin will absorb, and that limit is usually reached at about five minutes at 75-80 degrees with constant agitation. However, five minutes at 75 degrees with intermittent agitation gets you to about 95% of the maximum so that is where I usually work.I

Don't want to geek-out too much here, but the in the world of chemical engineering, the amount of developer absorbed into the emulsion is a mass transfer process. The mass transfer process, in this case the transfer of chemicals in Solution A into the film emulsion, is driven by the concentration of Solution A first and foremost. As usual, for a given concentration of Solution A, Sandy's information above is correct.

What is the point?

If you find that you need more development, increase the concentration of Solution A and Solution B and keep all the other development variables the same...

I had been using Pyrocat-MC at 1:20 dilution for both Solution A and Solution B. And, I found that I was not getting sufficient development in a few cases and generally could use more development. I now develop all my film with a Jobo processor at 75 deg. for 5 minutes using Pyrocat-MC at 1:10 dilution for Solution A and Solution B. This development has worked well for everything that I've tried thus far. I do develop different films together, e.g., TXP, FP4+, and Ekfe 25, that are exposed at the manufactures' rate film speed, and everything comes out well for scanning.

[sanking]

How does agitation increase absorption? How do you measure absorption? What is the goal in maximizing absorption?

At any given temperature and concentration maximum transfer of reducer into the emulsion is increased by agitation.

With any given film the more reducer you can get into the emulsion the higher will be the final contrast, keeping all factors equal with development in Solution B.

The goal in maximizing absorption is to adjust for the different absorption potential of different films, other factors kept the same. For example, if you develop TMY-2 the same way you develop Fuji Acros the former will have lower contrast than the latter. If you wanted to develop TMY to the same contrast as Acros you would want to increase absorption by either, 1) increasing the temperature of Solution A so the gelatin will aborb more reducer, or 2) increase the concentration of Solution A, say from 1:20 to 1:10, or 3) increase frequency of agitation.

In theory you could check for absorption by weighing a sample of film before and after it has been in Solution A but you would need a scale capable of measuring very small amounts. I actually do this with carbon tissue to determine absorption of dichromate but with film I don't believe my instruments have enough precision, so I test empirically by testing two samples, one with agitation and one without, then develop the two the same in Solution B. The only thing that could explain an increase in contrast, if you observe it, is the increased agitation.

Sandy

[Ken Lee]

Thanks -

I just read the recommended procedure on Pyrocat as a Two-Bath Developer on Pyrocat HD site.

I had missed a few important points, namely

• 1:10 dilution
  
• 5 minute pre-soak
  
• 6 minutes in Part A
  
• 5 minute post-soak in water

[Jay DeFehr]

Jay,

Varying the concentrations of the baths makes perfect sense to me, and is the approach I use when using Hypercat as a 2-bath developer. I use Hypercat A solution 1:10, and use a 1% solution of TSP as my B bath. My development times are much shorter than those reported here; I develop 2 min in A, and 1 min in B, at 70F. This works very well for me, even I'm very flat lighting. Is there some advantage to using a more dilute solution with longer development times?

[sanking]

Jay,

Varying the concentrations of the baths makes perfect sense to me, and is the approach I use when using Hypercat as a 2-bath developer. I use Hypercat A solution 1:10, and use a 1% solution of TSP as my B bath. My development times are much shorter than those reported here; I develop 2 min in A, and 1 min in B, at 70F. This works very well for me, even I'm very flat lighting. Is there some advantage to using a more dilute solution with longer development times?

The purpose of the longer development time of Solution A is to get 100% absorption, or close to it, without having to worry about temperature. You could also run Pyrocat with much shorter times if that is considered important but there would be some difference in final contrast between 5+5 and 2+2 depending on temperature. Development in Solution B is almost instantaneous as the image comes up immediately (as in pt/pd printing for example) but you can coax a bit more shadow detail from the negative with longer development times. Bottom line is that you won't see a lot of difference in final result between 2+2 and 6+6 but the longer times even out results without having to worry about temperature between 70F and 80F.

Sandy

[Jay DeFehr]

Sandy,

I'm afraid I still don't understand how agitation increases absorption, but I don't understand a lot of things.

It seems to me you're saying contrast is controlled by: time, temperature, concentration, and agitation in the A bath. If this is true, it seems to contradict a lot of the claims made for "automatic" 2-bath development. To develop to a predictable contrast requires a strategy, and considerable testing. Assuming development time in the B solution is non-critical beyond a minimum time for full development, one should still find it necessary to find the correct combination of time, temp, concentration, agitation in the A bath to achieve the desired contrast. What do you consider the best strategy for adjusting contrast? One strategy is to keep temp, concentration, and agitation constant and adjust time in the A solution. This strategy depends on the absorption rate of the film, which should remain consistent for any given film. This seems like a better strategy than adjusting the concentration of the A bath and keeping the absorption time constant ( maximum), because different images present varying demands on developer, ie a high key image requires more developer than a low key one. I don't think agitation offers much range as a contrast control, but temperature of the A solution might. It would make an interesting experiment, comparing the relative effectiveness of temperature v time as contrast controls. Time is almost certainly the most convenient control, but temp is not terribly inconvenient, especially when using automated processors. Still, if I was a betting man, I'd put my money on time in the A solution as the simplest, most effective contrast control.

[sanking]

There is definitely a lot of misinformation out there about two-bath development but I never worry about that because one can just step over all that and test to determine what is right and wrong. Another issue that needs to be clarified is that there are different kinds of two-bath developers. One kind is Diafine where all of the development takes places in Solution B (Pyrocat and I presume Hypercat are in this category), another kind is divided D23 where considerable development can actually take place in Solution A.

My own approach to two-bath development is to use it when your work flow does not require that negatives be developed to a certain contrast. If you scan it does not make a lot of difference whether your negative has a CI of .45 or .65, or even more extreme contrast than that. If you need to develop negatives to a specific contrast you are better off following Zone or BTZS type procedures with traditional one bath formulas.

If you must for some reason adjust contrast with two-bath developers the easiest way to do so is by adjusting the dilution of the reducer in Solution A. However, within limits you can also increase or decrease contrast by type of agitation in Solution A, and/or by length of time in Solution A, or by the temperature of the solution. In the article that I published in View Camera a couple of years ago I found that with most films using both D23 and Diafine it was possible to approximately equal contrast with rotary/continuous development compared to normal intermittent development by using a weaker dilution, say 1:120 instead of 1:10.

The amount of control possible with temperature and time is limited by a finite amount of solution that the gelatin can absorb, and heating it more and/or leaving the film in the solution for a longer period of time, will not in result in more absorption.

All that said, if one has a need to develop film to a specific CI I would recommend traditional one bath development with time and temperature control, not two bath development.

Sandy King

[Ken Lee]

Patrick
Sinar P, 450mm Fujinon C
5x7 HP5+, Divided Pyrocat HD


Lake, Massachusetts
Sinar P, 450mm Fujinon C, Light Yellow Filter
5x7 HP5+, Divided Pyrocat HD

There are all kinds of scenes that I now look forward to shooting.

They posess a special richness and subtley of tone, but were previouly out-of-bounds because of their impossible contrast range. Now, they are laughable.