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Photo Forum / Film Photography / Darkroom / December 2004phenidone-aminophenol
Hi all, Is phenidone-A superadditive with para aminophenol? Is there a simple experiment to find this? Any information in this regard much appreciated. thanks in advance, Sreenath >Hi all, > [quoted text clipped - 5 lines] >thanks in advance, >Sreenath Congratulations, Sreenath, you have asked a significant question that has been long overlooked; admittedly, by me, despite long years of playing with oddball agents and combinations. I do recall something that was kicked around about combining an Xtol type of developer with Rodinal, that might serve to get you going. Do an online search in newsgroups for Vitamin C and Rodinal, as that just may be the most specific combination. Robert Vervoordt, MFA > Hi all, > [quoted text clipped - 5 lines] > thanks in advance, > Sreenath Why? It would be difficult to combine these developing agents, as para-aminiohenol is usually used at a very high ph, whereas phenidone is usually used at a low ph. > > [quoted text clipped - 13 lines] >is usually used at a low ph. > That's not much of a clue. Hydroquinone is often used at high pH, as is ascorbic acid, but in combination with phenidone the pH may be much lower. Phenidone is often thought of as a catalyst for the other developing agent. In my experience, p-aminophenol is superadditive with hydroquinone or ascorbic acid in about the same way as metol. I have not tried it with phenidone. Phenidone and metol are actually antagonistic in some circumstances. >> >> [quoted text clipped - 23 lines] >phenidone. Phenidone and metol are actually antagonistic in some >circumstances. So, you're the one! :) Actually, there was at least one other who did some experimenting, but I forget who it was. That said, I wonder if your experiments might have included something like the Acufine substitute or Crawley's FX-11, in which both Phenidone and Metol were used to wring out some more emulsion speed? I;m aware that you avoid high Sulfite developers, so you may not have tried them, I did and they did deliver the goods. I'm trying to recall another instance of the two combined for some specific use, but am unsuccessful. I did use Phenidone and Metol in some of my own Cibachrome experiments, but, while they worked, they didn't produce the results I was seeking. Maybe somone can chime in here. Robert Vervoordt, MFA > Hi all, > [quoted text clipped - 5 lines] > thanks in advance, > Sreenath I don't think they are, at least significantly. p-Aminophenol is a close relative to Metol but generally considered inferior to it. Its used in Rodinal because it will dissolve in enough quantity to make very concentrated solutions. It was also thought not to a alergin like Metol, but it turns out that nearly all photographic developing agents can be sensitizers to some degree. The interaction of developing agents is complex. The superadditivity of Metol and Hydroquinone is very well known. The two tend to regenerate each other even in low pH solutions like D-76 where the Hydroquinone is not active as a developing agent. Ascorbic acid is superadditive with Metol and Phenidone is a similar way to Hydroquinone so can be used in developers in a similar way but with some adjustments. I just can't see any advantage to using p-aminophenol since it was long ago abandoned in all but highly concentrated developers and has been abandoned for those in favor of Phenidone (Kodak HC-110, etc.) except for Rodinal.  Signature--- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com > > Hi all, > > [quoted text clipped - 25 lines] > those in favor of Phenidone (Kodak HC-110, etc.) except for > Rodinal. Thanks for all the responses. I have rather large quantities of both these chemicals(phenidone and aminophenol) and don't want to buy any other developing agents. Actually, it is not true that aminophenol needs high pH to develop. There is one Kodak formula DK-93 that uses Kodalk as the alkali. I have made that developer, leaving the hydroquinone, and even that develops paper very well. Induction time was more than ID-62, which is my normal paper developer. While metol and phenidone are used in very small quantities compared with hydroquinone, rather large quantity of aminophenol is used. In DK-93, for 5 grams of aminophenol, there is just 2.5 grams of hydroquinone. Does that ring any bells? How does one determine experimentally if phenidone and aminophenol are superadditive? Any suggestions? thanks, Sreenath >I just can't see any advantage to using >p-aminophenol since it was long ago abandoned in all but >highly concentrated developers and has been abandoned for >those in favor of Phenidone (Kodak HC-110, etc.) except for >Rodinal. A couple reasons I can think of : 1) p-AP does not produce dermatitis as does Elon-based formulas for some people. 2) I believe it's more stable in solution. 3) p-AP generates less fog. Unfortunately p-AP is somewhat more expensive (nearly 2X last I looked) then Elon. Regards, John S. Douglas, Photographer - http://www.puresilver.org Please remove the "_" when replying via email >Hi all, > >Is phenidone-A superadditive with para aminophenol? No. >Is there a simple experiment to find this? The only thing I can think of would be some densitometric tests showing speed-point comparisons. To the best of my knowledge the super-additivity feature of PQ and MQ developers depend on the fact that the by-products of hydroquinone are developing agents in themselves. >Any information in this regard much appreciated. I'd try something like the following for a P-pA developer. 5.0g p-AP 0.20 Phenidone 50g Sulfite 2.0g Metaborate Starting time I would guess around 12 min. at 70F but that's purely conjecture. Regards, John S. Douglas, Photographer - http://www.puresilver.org Please remove the "_" when replying via email > > [quoted text clipped - 35 lines] > Please remove the "_" when replying via email > To identify and quantify superaddivity, do an experiment in which the amount of one is increased while the other is held constant, but keeping pH and sulfite content constant. Also do the experiment where one is increased while the other is left out. The experimental result is to be the contrast index (or gamma, if you're old fashioned) for constant time and temperature of development. I have done some such experiments with phenidone and sodium ascorbate, holding phenidone constant while varying the ascorbate. Sodium is a nearly neutral salt, so pH did not change appreciably. The result showed a curve that is much like the charging curve of a capacitor from a constant voltage through a resistor. The ratio of ascorbate to phenidone by weight at which the curve had pretty well levelled out was 80:1, although the usual 40:1 ratio came cery close. > >> Is there a simple experiment to find this? > > The experimental result is to be > the contrast index, or gamma, ... for constant time > and temperature of development. Something to look at and measure. I'd think paper would do well for testing. Is that the only observation to be made? Is that the only effect of superadditivity; varying gamma? I'm interested in what causes superadditivity. I think it may be no more than insitue regeneration. Dan > > >> Is there a simple experiment to find this? > > [quoted text clipped - 7 lines] > I'm interested in what causes superadditivity. I think it may > be no more than insitue regeneration. Dan 'Superadditivity' refers primarily to the effects of regeneration. See Jacobsen and Jacobsen. |
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