In the safety data sheet for Adox HC110 Pro, it contains hydroquinone and a phenidone derivative and it also contains Pyrocatechol.
Does anyone know what the Pyrocatechol does, besides the hydroquinone and Phenidone derivative?
Superadditive
Yes, but so is the hydroquinone. I'm wondering if it helps to control contrast or to improve sharpness in some way.
Looking at the pH of HC-110 (around 9.1 in a typical dilution) pyrocatechol is borderline active on its own. Superadditive effects are not as simple as it seems on the surface. In this case you have a few agents that interact with each other in ways that may be more complex than simply one recharging the other. You may also have different agents active in different regions of the film (e.g. edge of highlights vs highlights vs deep shadow) during development due to localized pH changes and dilution, and the build up of development products.Yes, but so is the hydroquinone. I'm wondering if it helps to control contrast or to improve sharpness in some way.
Looking at the pH of HC-110 (around 9.1 in a typical dilution) pyrocatechol is borderline active on its own. Superadditive effects are not as simple as it seems on the surface. In this case you have a few agents that interact with each other in ways that may be more complex than simply one recharging the other. You may also have different agents active in different regions of the film (e.g. edge of highlights vs highlights vs deep shadow) during development due to localized pH changes and dilution, and the build up of development products.
Thanks. I didn't see any mention of Pyrocatechol in Ilfotec HC which is designed to be similar.
Perhaps Ilford didn't consider it to be a necessary component. I was just wondering why Kodak included it in HC110?
I am interested as well It must add something or specifically react with something to improve the HC110 performance but so far I am nor clear what this is
Perhaps the question that is required is: What does Ilfotec lack without Pyrocatechol compared to HC110?
pentaxuser
In the safety data sheet for Adox HC110 Pro, it contains hydroquinone and a phenidone derivative and it also contains Pyrocatechol.
Does anyone know what the Pyrocatechol does, besides the hydroquinone and Phenidone derivative?
In the Film Developing Cookbook 2020 p75-6:
"HC-110 [that would be the discontinued Kodak product] is probably the only commercial Kodak formula to use it, or to have ever used it. The question is why? It is most likely that Henn and his team found what Crawley and Lowe did: it is hard, though not impossible, to make a sharp developer with phenidone and hydroquinone alone. An additional agent is necessary to mediate PQ's overactive regeneration kinetics. It is also possible that the pyrocatechin may help HC-110's noted stability, but its stability is probably mostly due to the absence of water in the concentrate."
It may be noted that the bulk of the constituents in the Adox product are not disclosed, but the results do not seem to be detectably different from those using the discontinued Kodak product.
That's just not correct (the cookbook stuff about PQ and sharpness).
Makes me think that it could be worth adding some Pyrocatechol to PC-TEA to see if it makes a difference.I am not saying you are wrong but google AI seems to concur with the FDC:
Activity at pH 9
It seems to have figured this out for itself as the references it gives are not really relevant.
- Threshold of Activity: The threshold of activity for Catechol is around pH 9.0. At this level, it is just becoming active, which allows for a controlled, slower development that often favors higher acutance through localized exhaustion at the edges of high-density areas.
- PQ Optimisation: Standard PQ developers are typically optimised for slightly higher pH levels (around 9.8 to 10.4) to achieve their best performance. At a lower pH of 9, a PQ developer might be "finer grained" but will typically lack the biting sharpness of a catechol-based formula.
I am not saying you are wrong but google AI seems to concur with the FDC:
Activity at pH 9
It seems to have figured this out for itself as the references it gives are not really relevant.
- Threshold of Activity: The threshold of activity for Catechol is around pH 9.0. At this level, it is just becoming active, which allows for a controlled, slower development that often favors higher acutance through localized exhaustion at the edges of high-density areas.
- PQ Optimisation: Standard PQ developers are typically optimised for slightly higher pH levels (around 9.8 to 10.4) to achieve their best performance. At a lower pH of 9, a PQ developer might be "finer grained" but will typically lack the biting sharpness of a catechol-based formula.
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