View Full Version : PMK, Blotchy Skies, and a Pyrocat Question

Peter Lewin
5-Sep-2014, 15:58
Some of you may have seen my Liberty State Park photos of the Freedom Tower and the NY skyline in the "Urban Images" thread. The first batch of negatives suffered from very uneven skies. I realized I had become rather casual in my tray development, and had to re-visit the scene and expose a new bunch of 4x5 to process more carefully. Now if I was trying to scientifically find the culprit, I would have changed one variable at a time, but of course all I wanted were clean, even negatives.

So essentially all I did was be more careful. The biggest change was to increase my developing time by decreasing my temperature, to allow for more even development. My "normal approach" had been to develop with PMK at 75F to decrease the tray shuffling time. I went back to the "standard" 70F, still using my ZoneVI compensating timer to handle the temperature change without my having to worry about actual "tray time," other than to know that it was longer at the lower temperature.

The other major change was to use an 8x10 developing tray, rather than the smaller but deeper food container I had been using. I figured that if agitation pattern "eddies" were having an effect, the larger tray would minimize them. These two changes, plus making sure that I was using fresh fixer, seemed to do the trick for me. Still not sure exactly what caused the blotchiness last time, I suspect the change with the greatest impact was lengthening the development time, but I'm happy that this time my open skies look OK.

Now for my question about Pyrocat HD. I made two identical negatives of each exposure, so I still have 7 sheets to develop. I expect Pyrocat HD to arrive next week. I exposed all the sheets at my PMK normal for HP5+, 320 ASA. The "giant developer chart" online (probably the wrong name but most of you know what I'm referring to) indicates times for Pyrocat around 9 minutes for HP5+ at 200 ASA, or something like 17 minutes (which seems very long!) for HP5+ at 400 ASA. Does anyone have suggestions how I should handle the negatives?

Alan Curtis
6-Sep-2014, 07:44
This may be of no help to you but this summer I used Fred Newman's film development service with HP5+ and Pyrocat HD. I was using the 2:2:100 dilution. The normal development time was determined to be 7:30 and the ASA was 400. I also use a ZoneVI compensating timer. The different factor is that I use BTZS tubes with Pyrocat HD, with HC-110 I tray develop. Great pictures by the way.

6-Sep-2014, 12:49
For Pyrocat-HD times, start with the ones found on this page:

www.pyrocat-hd.com and click on the suggested dev. times at the top. There should be times for HP5+ there.

Peter Lewin
6-Sep-2014, 12:54
Alan, NPR: Thanks for responding. NPR's link had exactly what I needed as a starting point. It will be interesting to compare the identical negatives in PMK Pyro and Pyro at HD.

6-Sep-2014, 15:34
I think PMK is a very nice developer, but it is less forgiving with regard to agitation and needs plenty of time. I usually use pyrocat hd.

David Schaller
6-Sep-2014, 17:06
Hi Peter,
I think your EI was about right, and I would say that in trays, with agitation the first minute then 10 seconds per minute thereafter, 12 minutes at 70F would be my N development. This is in the ballpark of the chart mentioned above (15% more time than rotary processing). With roll film I agitate even less and use an EI of 250. As mentioned, Pyrocat is more forgiving than PMK.