Quote Originally Posted by jdef
Sandy posted while I was still typing, but he makes some interesting points.



"As for the TEA, no, in my opinion it does not provide any benefits over carbonate or metaborate accelerators other than the convenience of single solution and stability."


That is probably true, but for me, those are important benefits.


"The formulas that I have prepared with TEA work at a pH of about 9.3, slightly lower than the pH of 9.6 of PMK, and quite a bit lower than the 10.9 of Pyrocat-HD."


Sandy, I'm not sure why the Ph is so important to you. Could you please explain why it is? I know that the Ph of a developer has an effect on its activity, and a developer with low Ph could have inconveniently long developing times, which is definitely not the case with the TEA developers I'm using, but is there something else that makes a higher Ph important?

"In fact, there are some real problems with the Pyro/TEA formulas if you use them at other than the standard dilution because this will result in very large changes in pH and in the activity of the working solution."

That's an interesting claim. I spent the better part of yesterday testing various developers with Technical Pan, and one of the clear winners was Pyro-TEA @ 1:200 for 10 min. @ 70F, the standard dilution being 1:50. Pyro-TEA and Technical Pan is a fantastic combination, by the way, and I imagine that it would be useful for other high contrast, fast developing films as well. Could you expand on your problems with Pyro/TEA developers and non-standard dilutions?
You misunderstood my point about pH. High pH is not desirable in theory. In fact, to the contrary as much of the literature suggests that *low* pH is better than high pH if small grain structure is desired. My point was that I could find no difference in grain with the various developers ranging from pH of 9.3 to 10.9.

When you dilute a Pyro/Tea formula there is a much greater change in pH than when you dilute PMK or Pyrocat-HD by an equal amount. Just test it yourself and you will see. This is a potential source of trouble, especially when you are trying to get as much contrast as possible out of an emulsion because if the developer exhausts too quickly because it is too energetic there will be oxidation and greater B+F.

Technical Pan is a high contrast film and one would expect that a much less energetic solution would work best with it. But I am not sure what you mean by clear winners? What other developers did you use for the comparison tests, and at what dilution and temperature? And on what do you base your conclusion that Pyro-TEA at 1:200 was the winner? Densitometry, comparison of print from different developers, or visual evaluation of the results of the negatives?

Sandy