In testing an idea with EXF where I combined ferrous sulfate, hydroquinone, triethanolamine, and carbonate I observed that the developer continued to work for a good amount of time in a beaker, several hours. I wanted to do a control test to see what ferrous sulfate was contributing to the process though. I made the same solution, but with no ferrous sulfate, and ensured that the pH of both solutions was the same. The results were incredibly surprising. The “control” without ferrous sulfate stayed alive for a very long time. Still producing images after 8 hours, though at around 300% slower speed. This seemed promising though, since there in theory was only hydroquinone acting as a developing agent and even if a lot of the hydroquinone oxidized, as long as some was alive infectious development should be possible…
But once again I’m smacked with abrupt failure when trying a similar concoction, EXH1, in a tray with actual paper tests. The developer works for a long time, can develop good blacks, and develops fairly quick at room temperature, but does not exhibit any infectious development. It also requires a lot of bromide to reduce fogging levels. The exact formula is as so:
2L water
Triethanolamine (TEA) 100ml
Potassium carbonate 12g (6g of 20%)
Hydroquinone 1g (in propelyne glycol 10%, 10ml)
2g of bromide (20ml of 10%)
The very high amount of TEA seems to preserve the hydroquinone quite well though the solution does quickly discolor.. However, a big give away is that there is very little red film present on the developer after a few minutes. It also does not give any infectious development, nor other hallmarks of lith printing like colorful highlights. In this the induction period seems to blur into shadow and black development, meaning that with more development the entire image gets darker and more highlights become present. I tested this on many papers, including Kodabrome which is a very good lith paper in traditional formulas. My hypothesis for the reason behind this failure is that TEA reacts, not with hydroquinone nor benzoquinone, but rather reacts with the radical semiquinone to produce some kind of complex which either is a weak developing agent or is not active. In this respect, a large surplus of TEA reacts in the same way as a surplus of sulfite would, it scavenges oxygen and preserves the hydroquinone, but also scavenges the semiquinone and prevents infectious development. With this in mind, HQ mixed into propelyne glycol would be a better “part A” than HQ mixed into TEA. With a lot of research, I’ve found this is a big subject area with very little or no previous research written about it.. However, TEA with other quinone compounds is known to form complexes with semiquinones and is also an electron donor, meaning it can potentially convert semiquinone back to hydroquinone. It appears to be an imperfect preservative compared to sulfite, since the solution will quickly discolor to brown, but either way the end result is that this is a major dead end into a fair number of ideas I had about this. I’m not really sure what else can be done at this point.