Re: Do dichromates change with age?
It could also have been someone British. I think all of the dichromates that Terry King and myself used when we started in alt processes around 1980 were surplus stock I liberated from the college where I worked which for some reason had ancient glass jars of the stuff that were never used, with very large crystals and no indication of purity - so we mainly used rather more recent reagent grade material. The college had been set up around 1910 (my mother was one of its students about 5 years later) and I think it likely that this also dated from the 1920s or 30s. One of the cases of early materials being significantly different in photographic use is that silver nitrate solutions were often significantly acidic and to get some processes to work as well as they used to needs a couple of drops of nitric acid to be added with modern materials. Regards, Peter Peter Marshall - Photographer, Writer: NUJ petermarshall@cix.co.uk _________________________________________________________________ My London Diary http://mylondondiary.co.uk/Re:PHOTO http://re-photo.co.uk London's Industrial Heritage: http://petermarshallphotos.co.uk/ The Buildings of London etc: http://londonphotographs.co.uk/ and elsewhere...... Judy Seigel wrote: On Mon, 14 Jul 2008, Loris Medici wrote:That could have been me.... maybe 10 (or so) years back, they emptied out a closet of old chemicals at Pratt, and through some chain of association a very large, somewhat antique-looking bottle (like maybe 1920s) maybe 1/3 full of ammonium dichromate, came my way -- and seemed to work fine. I didn't test its speed against the more recent one I'd been using (and who knew how long that had been in the bin at the supplier before I bought it?), but it seemed to work about as usual, and, since I generally develop by eye, I let it go at that. I probably have some of it around still, but my studio has piled up like the Mississippi delta... not sure I could find it today, or that I didn't rebottle in smaller container....I remember reading someone (British?) using NH4Di (maybe it was KDi) as old as 30 - 40 years in the list archives but I'm not sure...
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