Photo Engineer said:The original URLs posted by Titrisol of the work done at RIT refers to recent work.
This entire subject has been known about 100 years, and is reported on in the Haist Book, "Modern Photographic Processing" and has also been mentioned in Anchell and Troop.
PE
nspatel said:I checked out the original urls in the Titrisol's posts and it was everything that I had read before I started experimenting. I will have check out the Haist book though.
Basically what I was trying to do was utilize the coffee with develop times that were more reasonable. Adding the Ascorbic Acid and Phendione definately helped, but it makes me wonder if there is any merit to mixing develop agents that are not superadditive. I guess there are comercial developers do this to some extent. It seems like mixing a low contrast and a medium or high constrast developer would be beneficial but it is likely that the faster acting developer will dominate the reduction process. Especially if each of the develop agents respond differently to temperature.
Right now I am working on splitting out the developers into 2 baths to try to utilize the benefits of each(although at the cost of small develop times). One bath uses just coffee as the develop agent and the other just uses the ascorbic acid/phenidone combo with less alkali to make it less aggressive.
The idea is that the coffee will render the bulk of the image without the full density. The ascorbic acid/phenidone will just bring the density up in the darker areas to get more blacks. The limited work I have done so far seems to show this behavior but I don't think I have enough data yet.
Photo Engineer said:When you mix developing agents and see a big boost in activity, you never know what went on. Was it a superadditive effect or was it just the new developing agent being more active.
When you add an auxiliary developing agent to one of the coffee based developers, often the auxiliary developing agent takes over as the primary developing agent and you don't realize it unless you do lots of check experiments.
This is a very chancy thing to do and claim this or that mixture works. It may be that you could get along with another mixture as well or better. I think that you are very wise to say you don't have enough data yet. Keep at it though, there is a lot to discover out there.
PE
nspatel said:My bosses at work do a fine job at concluding things with too little data.
Would you know where I could could find good reading on superadditivity? My internet searches have not been so fruitful. I am looking for a semi-technical to technical explanation of what is going on.
Photo Engineer said:I'll suggest two authors with good work on the subject.
Mees and James "Theory of the Photographic Process"
Haist "Modern Photographic Processes" (2 volumes)
I think I got them both right.
PE
Donald Qualls said:I can't talk about developing paper in coffee or acetaminophen-derived p-aminophenol developers since, with about 85% of a five gallon box of Dektol to use up, I'm staying orthodox with my prints, but *film* has no incorporated developing agents -- and I routinely develop films of a couple varieties in both Caffenol and Parodinal.
Fomapan 100, aka Arista.EDU Ultra 100, processes well in Caffenol, though it seems to give little stain; Tri-X 35 mm looks very grainy in a scan after Caffenol processing, but the stain image masks the grain and can produce 8x10 prints from 35 mm that show no visible grain. I haven't yet tried Classic 400, aka Fortepan, in Caffenol, but it works very well indeed in Parodinal (as does .EDU Ultra/Fomapan 100) -- for that matter, so does Tri-X, though I don't know that I'd want to put 35 mm Tri-X in Parodinal.
NONE of these good to excellent results can be due simply to the alkali reacting with "stuff" already in the film -- they can only result from actual developing agents in the developers.
FWIW, when I've read about coffee developer for paper, ISTM they talked about it being very slow (as it is with film); you might try a non-DI paper (like, say, Forte Elegance FB) with dev times allowed to run as high as ten minutes, to see what you get.
nspatel said:For film what kind of develop times are required with caffenol?
Maybe yes, maybe no. Remember ascorbic acid is also an antioxidant like sodium sulfite. Addition of sufficient sulfite to a staining developer will also prevent the stain from forming.Donald Qualls said:the resulting Caffenol C gets the job done in about 12 minutes, but gives effectively no stain; my suspicion is that the vitamin C is doing effectively all the work at this strength.
Gerald Koch said:Maybe yes, maybe no. Remember ascorbic acid is also an antioxidant like sodium sulfite. Addition of sufficient sulfite to a staining developer will also prevent the stain from forming.
Gerald Koch said:Maybe yes, maybe no. Remember ascorbic acid is also an antioxidant like sodium sulfite. Addition of sufficient sulfite to a staining developer will also prevent the stain from forming.
nspatel said:I didn't realize that antioxidants will curb staining. I thought that the reduced stain after adding ascorbic acid was simply because the total develop time was less.
jsouther said:[...]
4 teaspoons washing soda
8 teaspoons instant coffee
I mixed the Vitamin C first till completely dissolved (@ 75 degrees), then baking soda till completely dissolved, then coffee till dissolved.
[...]
for Tri-X and Fomapan 100, about 30 minutes -- this is at 68-70 F, with agitation ten seconds out of each minute.
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