View Full Version : Yet another Pyrocat-HD question...

Tim V
15-Apr-2019, 01:47
Hi all,

A quick question that hopefully has a relatively simple answer... Iíve read Sandy Kingís website and a few others to find information on what Iím after but with no luck so far...

Normal dilution for Pyrocat-HD for negs aimed at silver printing on VC papers is 1:1:100, but I know a stronger 2:2:100 dilution is often used if doing 5 sheets of 8x10Ē film at a time in an Jobo 3005 expert drum, where the max chemistry load is 1L and exhaustion is likely with standard dilution.

My question is this: how much more active / faster working is the 2:2:100 dilution relative to standard dilution? Is there a standard formula or rule of thumb I can go by to convert a 1:1:100 dev time for a given film to 2:2:100 at the same temp, or is very much emulsion specific and too variable to predict?

For context, Iíve already got good data for times with some films thanks to Sandyís great work and helpful information provided by people here, but have decided to bite the bullet and order another box of Pancro to test and the only data I have for it (supplied by Bergger) for Pyrocat is:

Dilution 1+1+100
Tempťrature 24įC
Speed 200 : 17 minutes (contrast 0,65)

The time seems very long-although all of their recommended times are-especially at that temp, and I donít think standard dilution would hold up that well with 5 sheets in rotary processor for that length. 2:2:100 seems a better option to guard against exhaustion and would cut time down, my question though is by how much? Beyond Pancro, Iím interested in the answer / formula / rule of thumb guide so I may apply it to other films I might want to try where information is scarce.


16-Apr-2019, 04:25
What scares me is you are willing to risk 5 sheets of 8x10 without testing first and you have a semi automated processor which would allow for custom variation by scene.

I'm with the "gotta test it crowd" on this one. Start with your best guess and 5 similar scenes with one being a gray scale strip.
You can also get creative with your dark slide and create an image on one sheet that is exposed as 100/200/300/400 EI . - sunny 16 = 1/400 . Expose-cover 1/4, expose cover 1/4 until you reach 4 exposures 4x1/400 = 1/100

How many ml of part A/B at 1/1/100 do you need for 5 x 8x10 inches for normal films? - Cut water volume in half .
Adjust time for stronger dilution - ?
Then add time for Bergger 20-30%, Then reduce time for processor 15-25%.
Lets say that is 16 minutes - look at your negatives and decide if you need more time or less.

Tim V
16-Apr-2019, 14:23

I'm crazy but not so crazy as to dive in head first developing 5 precious images. Thanks for the concern though, sometimes I do need a good reality check!

I'm interested most in finding out how to calculate–even in a general, rule of thumb sense–how to determine a 2:2:100 dilution with reference to a given 1:1:100 time. The naivety of my question might have something to do with failing chemistry at school (by a wide margin,) and perhaps I'm simply assuming wrongly that it's even possible for such a rule to be determined.

Your advise is good though, thank you. It's a great starting point.

16-Apr-2019, 15:48
I'll post my data for you. It has everything you'll need if you are using a Jobo 3006. The agitation during development does change things somewhat so whatever you are using, if it equates to what I have, you should achieve similar outcomes. Try to keep temperature, dilution, agitation the same or very similar.

I do not use Pyrocat-HD at 1:1:100. It is too weak at that dilution in my understanding. All my tests are done with calibrated instruments. My data is a little over the top for many I guess but it should give you a good understanding of what is happening with development times and ISO etc. It is all colour-coded to help and remind your understanding. Although I have experience like this with a few films, my guess is that all films will be similar. If you have a film of say, ISO 200 on the box, then expect to reduce it by a similar amount in practice.


Pere Casals
16-Apr-2019, 16:07
I'll post my data

Thanks for posting that information, really interesting.

Just a question, when you say "In shooting, place the dark areas about -2.5 stops down from ĎZoneí 0" , what you mean ? Is 0 the metered exposure ?

16-Apr-2019, 17:43
Yes Pere.

Setting the ISO to whatever column and then spot metering the subject. So you would spot the dark shadows and expose about 2.5 stops faster shutter speed. Assuming a 'landscape' of some description !

If it were a portrait, I'd probably go with an incident reading at the face of the subject and perhaps expose a little more (up to a stop) for a darker skinned person and expose a little less for a lighter skinned person.

Tim V
17-Apr-2019, 00:27
Wondering how or why you standardised in only 6rpm using the expert drum? I’m guessing that’s a lot slower than any Jobo or motor base would go, but assume you do it to minimise oxidisation?

17-Apr-2019, 14:59
Correct Tim. Oxidation plays a big part in a number of developers. That is why professional labs have Nitrogen on top of their tanks. They circulate the developer liquid by pushing bubbles of Nitrogen through the developer.

So... a motorised Jobo is like a washing machine tumble dryer. It is extremely poor for oxidation-sensitive chemicals in my opinion.

I use a Jobo roller base in a tank of temperature-regulated water and turn by hand.

It is a good thing to use a slightly stronger developer mix to bring down the developing time which in turn limits the effects of oxidation also.


10 seconds per rev.

Tim V
18-Apr-2019, 01:38
From what I can gather the slowest speed of my CPP3 is approximately 25rpm, so not crazy but certainly not close to 6!

For 5 sheets of 8x10” film with the expert drum and max of 1L, i cant see a dilution of 1:1:100 cutting it, no matter what film, but especially a film like Pancro that requires a good 17mins in the dev even at 24 degrees. 2:2:100 seems the only way to go, so I’ll need to estimate the time difference and do some testing. Your tests are very helpful, thanks. I use a lot of HP5+ so the information is invaluable to me for using it, but also gives some insight into how to predict how other films might react to using non standard dilutions.

18-Apr-2019, 15:21
A thought on testing the dilution. Expose your 8x10 sheet and cut it in 4ths .

Take one of the fourths and put it in a tank and process with 1:1:100.
Do same time for another fourth with 2:2:100
-- compare the difference.
You still have 2 fourths to play with to determine the amount of time needed to match your 1:1:100 time. Lets say thats 35% less.
Then you can take that factor and apply it to your processor time - should be in the ball park.

Tim V
18-Apr-2019, 18:30
Great idea! Don’t know why I didn’t think of this before.