Pyrocat HD dilution?

[James Morris]

I've just started using Pyrocat HD with HP5+, and am looking for any advice on dilution.

I'm targeting the negs for printing on Lodima, Azo and Pt/Pd. There are several different recommendations for dilution, with 2:2:100 suggested for this case, and also 3:2:100 and others.

What's the best starting point?

Is there any reason not to use 1:1:100 apart from longer developing times? Does dilution change the response curve significantly, for example?

[mat4226]

Have you seen this article on Unblinkingeye comparing Pyrocat HD dilutions?

http://unblinkingeye.com/Articles/PCat/PCat4/pcat4.html

I'd say these will give you a good starting point for your own testing. And if you're looking for an example of how a 1:1:100 dilution differs from a 2:2:100, compare Figures 8 & 15.

[James Morris]

Thanks. Interesting that it takes almost the same time to get to CI 0.7 on both curves, but changes dramatically at higher CIs.

[James Morris]

I'm also wondering why people use different ratios between A and B.

Increasing B would make A more active, right? Why do people have more A and less B? i.e. a stronger dilution but less active.

[Ken Lee]

I prefer a normal development time of at least 10 minutes: it affords some wiggle-room when developing many sheets at a time, particularly when developing by inspection. Using less developer makes it even more affordable too.

[Jay DeFehr]

James,

One might increase the A solution relative to B if one wanted to increase developer capacity without increasing the activity, or even while decreasing activity. This might be useful for developing high key negatives with rotary processing, for instance.

[sanking]

An assymetrical relationship of A to B in which A is in excess is useful for minimizing general stain from oxidation when developing film to the high contrast needed for some alternative processes. Dilutions of 3+2+100 or 4+2+100 will give both more overall energy and less B+F stain than a symmetrical dilution of 2+2+100.

Minimizing general stain is important in alternative printing because of the long exposure times needed for many alternative processes. An increase in general stain increases shadow density, which results in longer exposure times.

Sandy

[James Morris]

Thanks, Sandy, good to know if I run into problems with long printing times.

[Jim Noel]

It is interesting that I just completed a series of tests yesterday to determine the same thing.
I suggest you begin with 4:2:94. Good contrast increase w/o extra overall stain. I was able to keep the b+f to .16 on the blue channel of the denistometer.I do not have a UV densitometer.
If you use FP4+ rather than HP5+ it will be easier to attain the desired contrast since slower films expand much better than do fast films. Fast films are better at contraction.

[James Morris]

Thanks, folks.

Jim: I tend to need contraction more than expansion in the Australian light.


For anyone else looking for a starting point with this, I found 9m @ 20c worked well with 2:2:100 for HP5 with a normal SBR, for printing on grade two Lodima in Amidol.