Quote Originally Posted by nspatel
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.
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.