Pyrocat HDC

[Dario]

Hi folks

Can anyone shed some light on this question, please?

I note that most people make up a working solution of Pyrocat using equal quantities of Parts A and B (develop and alkali), e.g. 1:1:100.

What is the effect of varying the ratio of A to B?

Thanks.

[esearing]

From my experiments with FP4+ , SP445 Tank development, Pyrocat HD and Pyrocat M 70degrees F. Pyrocat C should behave the same unless you are using rotary - then you need to increase both.

Less B gives you a slightly lighter stain, but it can also make your developer less active to the point of underdevelopment. But is generally safe down to 1A:0.75B:100W.
If you are processing a single sheet of 4x5 you can also get away with less A and B but will need longer processing time. You have to experiment with what you want to use and observe the differences in the midtones and highlights.
I normally use 3.5A: 3B: 500 @70* in the SP445 tank for single sheets with 5-6 stop SBR image for 12:30-14:00 minutes . Add .5 ml of A and B for each sheet of 4x5.
For my 5x12 FP4+ negatives I use 15A: 15B: 1800w in a tube for 14Minutes at 70* and get negatives that print well on Grade 1.5-2.5 easily.
NOTE 3mlA for single sheet 4x5 is a bit weak for aged Pyrocat HD and can have problems even if using longer EMA/stand times. It will come out pinkish-tan.

Increasing part B makes your developer more active but also more alkaline and has risk of fogging. I have used at around 1A:1.25B to try and increase base stain but I have not seen any real difference or benefit to using more part B. I only did a couple of experiments with increased B so with the right image or alternative printing method to be used, there may be a valid reason to do so.

Simple test: Find a scene with 5-6 stops of shadow and highlight , having mid tone details and contrasts, then take 3 shots. Waterfalls on a cloudy overcast day generally work well because of dark wet shadows, dry rocks, greenery, and whitewater. Or expose film with a step wedge or controlled scene.
Develop each adjusting part B but same time and temperature and agitation. Contact print side by side at grade 2 to see the differences or use a densitometer. Differences may be subtle.

My standard print/paper developer is Ansco/PF 130 on glossy paper which gives contrast a boost to my eye, so you may need to adjust for your paper and print developer as well. I also like the look of Ethol LPD 1:4 on warmtone paper with images developed in Pyrcat Metol for a smoother gradient tonal image.

Point is you have to know your entire workflow to really see the differences of a little more or less part B.

[j enea]

Steve Sherman had a great quote that I think makes sense. this is from his great reduced agitation article on unblinking eye

"Think of the Pyro A component as gasoline, and the Pyro B component as the octane in that gasoline"

john

[Dario]

Many thanks for your replies. I'll experiment a little and see how I get on.