Article on Pyro Developers

[sanking]

[quote="john_s"]I

Is there a reason that in the massive amount of info that Sandy has produced and generously presented to us, there is no graph for HP5+ at 100+1+1 dilution? Obviously long development times might be an issue for some people, but an extra 5min would not bother me.



Yes, there is a reason. In fact two reasons.

First, I am primarily an alternative printer and for my own work use almost exclusively the 2:2:100 dilution. For the broader benefit of Pyrocat-HD users I have done some testing with the 1:1:100 dilution but not nearly so much as with the 2:2:100 dilution.

Second, every single one of the CI charts provided represents at least 3-4 hours of time. This includes:

1. Exposing five sheets of film for exactly the same time to a 21-point step wedge.
2. Developing each of the sheets of film for a different time (calculated from about 0.5X normal to 2X normal, assuring temperature control of +/- 0.5 degrees for all stages of processing.
3. Reading the densities of each of the five sheets at all 21 points of the step wedge. (5X21 readings = 105 total) Different readings are required for silver papers/AZO (Blue reading) and alternative processes (UV reading).
4. Entering the data into WinPlotter. (5X21 entries = 105 total)
5. Analysis of the curves and transfer of the graphics from WinPlotter to PhotoShop to Word.

As you can see, providing useful testing information takes a lot of time. If there are other WinPlotter users who would be interested in running tests and sharing the data for films (and/or dilution) that are not covered in the article I would be very interested in including CI charts of these tests, with credits.

Sandy

[john_s]

[quote="dnmilikan"]

First of all, film shot for enlarging is never developed in Pyrocat at a 2-2-100 dilution. The 2-2-100 dilution is for negatives designed for alternative process or Azo. That explains why your negatives are contrasty. If you take the 2-2-100 time on the blue channel reading of HP5 and use the same amount of time but cut the dilution to 1-1-100 you should be fairly close.

Thanks. I have been aware of Pyrocat-HD for a year or two and assumed that it would be less suitable for my purposes, ordinary silver printing on VC and occasionally on graded papers, using 120 and some 35mm. I use PMK generally and have been happy with it, except that I've experienced some variations when I've mixed up a new batch (despite being quite careful).

It was Sandy's recent article that prompted me to try his developer. Obviously one needs to be prepared to experiment when starting out on a new and rather different developer. What surprised me, and I still don't understand it, is that I chose the time for gamma=0.5 which I thought would have given me the level of contrast I was looking for.

Anyway, I'll follow your advice and report back.

Thanks again.

[sanking]

[quote="john_s"]
What surprised me, and I still don't understand it, is that I chose the time for gamma=0.5 which I thought would have given me the level of contrast I was looking for.

John,

Two quick notes.

First, I looked at my data again for the 2:2:100 dilution of Pyrocat-HD with HP5+ and it agrees with the chart in the artilce. For a CI of 0.50 my tests indicate that you need to develop HP5+ for about 6:30 minutes at 72F. This is based on a densitometer reading with the Blue channel and applies to silver gelatin printing.

Second, please note that at another spot in the article I indicated that persons experienced with PMK could correlate that information to the 1:1:100 dilution of Pyrocat-HD by multiplying the PMK time by 0.70. From that I calculate that for normal SBR scenes a time of about 9:00 minutes at 72 F would be about right for HP5+ when developed in Pyrocat -HD 1:1:100.

Hope this information is useful to you.

Sandy

[john_s]

Thanks Sandy. It is helpful. It won't take long to home in on the right time. My choice of .5 was just guesswork, since i don't do such measurements. My PMK times are shorter than normal for some unknown reason (not the water quality). I'm hoping that Pyrocat-HD will be more consistent for me from batch to batch. I currently have three lots of PMK all different, all carefully made at different times using chemicals from the same supplier.