Conventional anti-foggants for C-41-process B&W?

Dear friends,

 

I am working my way through a bulk roll of Ilford XP2 Super that I

bought for a ridiculously low price. It was several years past-date

when I got it and was probably poorly stored beforehand -- there is a

certain amount of fog as a result. It isn't horrible, but if I could

be rid of the fog I'd be happier.

 

In the next few weeks I will be processing some of it at home in C-41

chemistry. Will a fog reducer like KBr work as it does in B&W

chemistry if I add it to the C-41 developer? Can I start experimenting

with KBr concentrations used in B&W chemistry or does the C-41 process

react much differently to this additive?

 

Thanks in advance!

Hi Jordan, I'd guess that it ought to help. Definitely an ongoing C-41 process is sensitive to replenishment rates which indicates to me that byproducts (largely bromide) have a lot to do with it. Also, additions of "starter solution" have a large effect, and starter basically tries to "season" a mix by directly adding the rough equivalent of development byproducts. So these two things help support the idea that bromide additions will hold back the development.

 

I don't know about the home kits, but a typical production C-41 developing solution would run concentrations of roughly 1 to 1.5 grams/liter expressed as NaBr. If you were to try maybe a 20% increase, this would be roughly 1/4 g/l added as NaBr; the molar equivalent of KBr ought to be close.

 

Personally, I'd hate to ruin the C-41 developer just to use the cheap film. If you have some color film to process, why not do it first then add your KBr potion to the USED developer? I presume you're just playing with the film anyway, and it's not critical work?

 

Just to make sure you know, I'm making mostly educated guesses here, but you could take a look at the on-line Z manuals from Kodak if you want to check up on me.

Jordan;

 

Potassium Iodide also is used in C41 as an antifoggant and with seasoning in a normal process, phenyl mercapto tetrazole builds up.

 

PMT is a powerful antifoggant.

 

Ron Mowrey

Thank you both for the suggestions. I will try the KBr first and see how it goes. BTW, I don't plan on "ruining" a good batch of C-41 chemistry for this -- "critical" work will get done first, and most of what I will process with this batch will be the XP2 and very old medium-format VPS and VPL put through some old folders.

Freestyle Photo offers a hand process C-41 kit to make 1 liter and to make 64oz.

Jordan - I have a roll of XP2 (which I never use but I somehow have it) if you want. I also have lifetime supply of PMT (1-phenyl-5-mercaptotetrazole) which I can give you a vial of stock solution. A couple of milligrams per liter of working solution may be enough to see the effect.

 

Ron - doesn't iodide work somehow as an anti-restrainer in low concentration? I never read the mechanism but, perhaps, imperfect halide conversion in the developer solution increases the developability. Maybe you know the exact mechanism.

Ryuji;

 

I am going to have to wing this, as I don't really remember anything like what you are suggesting. You may be right.

 

Here is what I know. As iodide goes up in a developer or emulsion, development rate and fog rate go down. Solvent level increases in the developer can increase development rate of high iodide developers or emulsions.

 

There was a paper published on iodide in emulsions and developers, and the effects of solvent levels on rates of development and fog formation. I forget who wrote it, and the summary escapes me. I don't even remember where the report was published. Sorry.

 

Ron Mowrey

Thanks for the offer Ryuji, but I finished at "the Institute" last spring and we are no longer neighbours... Otherwise I would have gladly accepted your offer. This is mostly for fun (i.e. if I can't get useful fog reduction and/or there are other deleterious effects, I won't be crushed) so I think I'll stick to KBr for starters.

Benzotriazole, or pinakryptol yellow might be other options, or they might not. They both work as anti-foggants in B&W chemistry.

 

Jay