I started a thread a couple of days ago called And yet another pyrocat. The thread was started based on some preliminary testing I made in which ascorbic was substituted for one of the secondary reducers in the Pyrocat formula (for phenidone in Pyrocat-HD, for metol in Pyrocat-M or for p-aminophenol in Pyrocat-P).
After further testing, however, I concluded that the family of curves created by the pyrocatechin + ascorbic reducer was so significantly different from the family of curves of Pyrocat-HD, -M and P, which are almost mirror images of each other, that the term Pyrocat-A would be inappropriate.
There were also other problems. Since pyrocatechin and ascorbic are not super additive, the function of the ascorbic is solely that of a reducer/restrainer. In other words, the pyrocatechin is doing all of the work, unlike the other pyrocat formulas where the secondary reducer constantly regenerates, so to speak, the pyrocatechin. So pyrocatechin + ascorbic works much like a straight pyrocatechin or hydroquinone developer, i.e. slow working at first, but after a certain amount of time they build contrast rapidly within a short period of time. If you were to test film at 4, 8, 10, 13 and 20 minutes you would find that about 80% of the contrast is built up in the period between 10-13 minutes, or at least that is the case when used in the Pyrocat formula. If you test Pyrocat-HD, -M or P for the same amount of time, contrast is built at about the same rate for any specific duration of time between 4 and 20 minutes.
Another phenomenon I observed was that minor differences in type of agitation caused a very large difference in effective film speed. For example, in my initial tests I developed in a drum on a motor base running at about 75 RPM and film speed was comparable to what I get with Pyrocat-HD, -P and M at the same time of development. However, when I tested with development in tubes in a water bath with very gentle agitation, say 5-10 RPM, there was a loss of more than three full stops of film speed. This happened with the 1:1:100 dilutions using ascorbic in amounts ranging from 0.05g/liter to 0.15 g/liter in the working. I mention this specific fact because much of the discussion in the other thread focused on the "optimum" amount of ascorbic.
So, for those persons who followed the other thread I just want to clarify that my reasons for abandoning this line of experimentation relate primarily to what I perceive as some major problem with the pyrocatechin + ascorbic combination, not to the personal issues which surfaced in the thread.
Further, my comments are meant to apply only to my own testing of ascorbic as a substitue for another reducer in the Pyrocat formula, not to any similar formulas by others.
Sandy
After further testing, however, I concluded that the family of curves created by the pyrocatechin + ascorbic reducer was so significantly different from the family of curves of Pyrocat-HD, -M and P, which are almost mirror images of each other, that the term Pyrocat-A would be inappropriate.
There were also other problems. Since pyrocatechin and ascorbic are not super additive, the function of the ascorbic is solely that of a reducer/restrainer. In other words, the pyrocatechin is doing all of the work, unlike the other pyrocat formulas where the secondary reducer constantly regenerates, so to speak, the pyrocatechin. So pyrocatechin + ascorbic works much like a straight pyrocatechin or hydroquinone developer, i.e. slow working at first, but after a certain amount of time they build contrast rapidly within a short period of time. If you were to test film at 4, 8, 10, 13 and 20 minutes you would find that about 80% of the contrast is built up in the period between 10-13 minutes, or at least that is the case when used in the Pyrocat formula. If you test Pyrocat-HD, -M or P for the same amount of time, contrast is built at about the same rate for any specific duration of time between 4 and 20 minutes.
Another phenomenon I observed was that minor differences in type of agitation caused a very large difference in effective film speed. For example, in my initial tests I developed in a drum on a motor base running at about 75 RPM and film speed was comparable to what I get with Pyrocat-HD, -P and M at the same time of development. However, when I tested with development in tubes in a water bath with very gentle agitation, say 5-10 RPM, there was a loss of more than three full stops of film speed. This happened with the 1:1:100 dilutions using ascorbic in amounts ranging from 0.05g/liter to 0.15 g/liter in the working. I mention this specific fact because much of the discussion in the other thread focused on the "optimum" amount of ascorbic.
So, for those persons who followed the other thread I just want to clarify that my reasons for abandoning this line of experimentation relate primarily to what I perceive as some major problem with the pyrocatechin + ascorbic combination, not to the personal issues which surfaced in the thread.
Further, my comments are meant to apply only to my own testing of ascorbic as a substitue for another reducer in the Pyrocat formula, not to any similar formulas by others.
Sandy
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