what's the purpose of ascorbic acid in Pyrocat-HDC?
Which paramester determine the amount of ascorbic acid in Pyrocat-HDC (why 4g/l and not 40g/l)?
It's there as an anti-oxidant and replaces Metabisulphite which won't dissolve in Glycol.
Ian
Thanks. Are you sure? It's odd, since the glycol version does fine without an antioxidant in the first place.
I believe this is Sandy's earliest description of Pyrocat HDC, and includes his reasoning:
I believe this is Sandy's earliest description of Pyrocat HDC, and includes his reasoning:
How to super activate Pyrocat-HD
In case anyone is interested I posted a message this afternoon at the AZO forum on increasing the energy level of Pyrocat-HD, at Dead Link Removed This information should be useful primarily to photographers working with AZO #2 and with alternative processes such as carbon, Pt/Pd and VDB with...www.photrio.com
It's virtually always used as part of a superadditive pair, generally with phenidone, although I suppose it might also work with metol (never looked into it). But you could very well make an ascorbate-only developer. It'll require quite a bit of ascorbate and/or it might be slow. But still, it'll work. I think you can find some experiments along those lines also here on Photrio.I never encountered an ascorbic acid only developer?! So is the statement ascorbic acid is developer correct?
It's virtually always used as part of a superadditive pair, generally with phenidone, although I suppose it might also work with metol (never looked into it). But you could very well make an ascorbate-only developer. It'll require quite a bit of ascorbate and/or it might be slow. But still, it'll work. I think you can find some experiments along those lines also here on Photrio.
Whether we should label developers only by a single developing agent if they contain multiple...I don't know, but it's common to do it that way. We refer to staining developers as 'pyro' developers a lot, even if they also contain e.g. phenidone.
Staining developers are often called Pyro, but there are also Hydroquinone staining developers. and not all Pyro developers are staining.
This reminds me; I once did some experiences with a staining HQ developer. It worked fairly well, although it didn't give quite as pronounced a stain as pyrocatechol. In fact, I think at least part of the coloration you see on lith prints is actually due to hydroquinone stain!
And indeed, add sulfite to a pyrocatechol developer and it won't stain anymore. Didn't original HC110 contain pyrocatechol?
I try to stay away from staining lagers.
......... Didn't original HC110 contain pyrocatechol?
................
Yes, it sure stains the trays, so probably the paper too.I think at least part of the coloration you see on lith prints is actually due to hydroquinone stain!
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