How to super activate Pyrocat-HD
In case anyone is interested I posted a message this afternoon at the AZO forum on increasing the energy level of Pyrocat-HD, at http://www.michaelandpaula.com/mp/Az...GID=5999&CID=2
This information should be useful primarily to photographers working with AZO #2 and with alternative processes such as carbon, Pt/Pd and VDB with medium and low contrast films in low contrast lighting conditions. These conditions require developers of high energy to provide the CI necessary for these processes, where a CI of 0.75 is considered normal for N or SBR 7 development.
The variation of the Pyrocat-HD formula, which I am calling Pyrocat+, consists of adding 0.1g of ascorbic acid per liter of working Pyrocat solution. Adding this amount of ascorbic acid provides a significant boost to the energy level of Pyrocat-HD, without killing the stain, and will shorten times significantly with both the regular 1:1:100 and 2:2:100 dilutions. However, the primary benefit of the the variation would be for developing negatives exposed in low contrast lighting for processes that require a very high negative CI. And, since the stain is not affected by the ascorbic acid the benefits of the variation are equally pertinent to both AZO #2 and UV sensitive processes.
You really are a wealth of Knowledge. Would this help BPF 200/Classic 200 in low contrast situations as well?
In the post on the AZO forum you mention a dilution of 5:3:100. I don't follow the Azo forum anymore, so I have no idea what this dilution is about. What would this dilution be for? Over here I see 1:1 or 2:2.
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I read the post on the Azo forum and found that my questions had been answered, forgive this post.
Mark, the inherent characteristics of the film cannot be meaningfully augmented by Pyrocat+. In other words, Classic 200, in my experience, does not have a high enough CI to print well on new G2 AZO (at least most of the time) and using Pyrocat+ will not change that. Once a film's maximum CI is reached that is it.
Originally Posted by Donald Miller
The use of ascorbic acid is not an addendum to my earlier post about super activating with sulfite. The earlier post was designed to address one specfic issue, how to get as much contrast as possible out of old Super-XX film when printing on AZO.
However, as I noted at the time, the use of sulfite in the working solution is bad for alternative printing because it kills the stain, thereby lowering the overall conrtrat of the negative, even though the actual silver density may be higher.
What I have done with the use of ascorbic acid is give a significant boost to the developer activity of Pyrocat-HD, with any dilution ranging from 1:1:100 to 6:4:100, simply by adding 0.1g of ascorbic acid to the working solution. The purpose is to get as much contrast as possible from low and medium contrast films in flat light situations that are to be printed with UV sensitive processes.
Quite a number of folks have discussed the super-additivity of ascorbic acid with pyrogallol and pyrocatechin and there is a specific model that also combines Pyrogallol + Metol + ascorbic acid, i.e. the formula introduced by Harald Leban originally as ABC+, now sold as Rollo Pyro. When I originally developed the Pyrocat-HD formula back in the late 90s I experimented with the addition of ascorbic acid to the basic formula but abandoned the experiments because ascorbic acid in the amounts I tried, 0.5 to 1.0g per liter of working solution, killed the stain. Recently, motivated in part by Pat Gainer's experiments with ascorbic acid, I looked at the matter again and decided to try even smaller amounts of ascorbic, ranging from as little as 0.05 to as high as 1.0g per liter of working. The magic figure turned out to be about 0.1g per liter of working solution. At this amount there is a significant boost in the energy of the working Pyrocat solution, B+F is kept at a very low level, and the stain is retained.
If you were to compare the active reducing agents in a liter of working soluiotn of Rollo Pyro 2:4:100 and Pyrocat-HD 5:3:1:100 here is what you would have.
Rollo Pyro 2:4:100
0.1g ascorbic acid
0.1g ascorbic acid.
At these dilutions the Pyrocat-HD solution is quite a bit more energetic and will develop a film like FP4+ to maximum CI, about 1.2, in slight less than 12 minutes (rotary development at 72ºF).
Last edited by sanking; 12-06-2004 at 12:40 AM. Click to view previous post history.
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Originally Posted by mark
The dilution would be for persons printing with alternative processes that require a very high CI in the negative, and even more specifically when using low and medium contrast films in low contrast lighting situations. Silver printers, outside of AZO, should never have any need for this extremely active dilution.
And no, it would not help BPF very much. The problem with BPF is that it has very limited expansion and contraction potential and a relatively low maximum Dmax. I could state that positively by saying that it has excellent exposure and development latitude and when you expose it in the right lighting conditions it is almost impossible to make a catastrophic mistake in exposure or development. The very strong dilution of Pyrocat+ will develop BPF must faster than the regular 1:1:100 dilution but it will not give it more Dmax or make it better for N+ and N- development.
It is possible to increase the CI above that of the maximum silver image by using a staining developer. The stain image is added in proportion to the silver image for blue or UV sensitive printing materials as well as for VC papers with blue or magenta filtration. Furthermore, a silver image formed by a non-staining developer can be increased in contrast by bleaching in a ferricyanide-bromide solution and redeveloping in Pyrocat or other staining developer.
Mr. Gainer-could you please list the ingredients for the Ferricyanide-bromide solution?
I'lll chime in. For bleach and redevelop, it is only critical that you completely rehalogenate the image forming silver. So the chemical amounts just affect the time it takes to accomplish this. Try this:
Originally Posted by peters
15g potassium ferricyanide
15g potassium bromide
1 liter of water
Presoak the neg in a tray of water for five minutes or so, then put it into this bleach until the image is basically gone. The image will pretty much go away leaving a tannish looking very faint residual image. Rinse the bleach off in gently running water then redevelop in the developer of your choice. This is also a good way to make a Polaroid type 55 negative suitable for alt processes. i would suggest trying this on scrap negatives until you get your process nailed down adequately. Don't make your first attempt on 'Moonrise at Hernandez'
Clay-thank you very much for the information. I'm off to try it this morning
Have a great day