Using DAS to replace Potassium Dichromate in the Gum Bichromate process
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I agree with @koraks. There is probably no way to easily/simply substitute DAS for dichromate in gum printing.
However, you might want to take a look at the "The Chiba System" for an alternative chromate-free process that is similar.
Alas, detailed information on the best developed varient of this system which was announced here (see: https://www.photrio.com/forum/threa...hod-for-dichromate-free-casein-prints.178880/) seems no longer to be available as Heather's website does not appear to be working.
I just checked and the wayback machine might be useful, see: https://web.archive.org/web/20201110112331/https://www.heatherdaugustine.com/
Regards,
However, you might want to take a look at the "The Chiba System" for an alternative chromate-free process that is similar.
Alas, detailed information on the best developed varient of this system which was announced here (see: https://www.photrio.com/forum/threa...hod-for-dichromate-free-casein-prints.178880/) seems no longer to be available as Heather's website does not appear to be working.
I just checked and the wayback machine might be useful, see: https://web.archive.org/web/20201110112331/https://www.heatherdaugustine.com/
Regards,
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DAS works. See this link:
www.alternativephotography.com
I didn't try DAS myself, but I tried gum with Speedball diazo sensitizer, and that also works, though I didn't go beyond basic tests. (However, Speedball won't work with casein, since it contains phosphoric acid that instantly congeals the casein into a rubbery lump.)
Gum Diazo Printing v1.4 – AlternativePhotography.com
www.alternativephotography.com
I didn't try DAS myself, but I tried gum with Speedball diazo sensitizer, and that also works, though I didn't go beyond basic tests. (However, Speedball won't work with casein, since it contains phosphoric acid that instantly congeals the casein into a rubbery lump.)
Sorry for being lazy earlier, but I've looked up now what Calvin has to say about diazo in gum printing. He mentions it works well with gelatin and casein (pages 144-145) and even shows two examples. Indeed Kees Brandenburg (a Dutch alt. process, particularly carbon transfer, printer) offers workshops with 'zerochrome' casein printing using DAS (link is in Dutch, sorry).
Elsewhere in his manual Grier mentions that he hasn't found any alternative sensitizer that works well with actual gum printing. The inconsistency with this remark and the page linked to by @revdoc is likely associated with Grier's exacting quality requirements and the particular process he has devised to realize these. For instance, his approach to developing gum prints deviates from the norm - he uses an 'instant' development technique that relies on pH changes. This helps to reduce uncertainty and variation between prints. I'd have to re-read his manual, but I recall this being the cause of DAS not being a suitable candidate for his approach to gum printing. Staining was also an issue, with the permanganate clearing bath likely degrading the gum layer too much. This is also alluded to on the hum diazo printing page where it's stated that prolonged clearance can reduce density in the shadows. I'd wager to say that prolonged permanganate clearing probably reduces ALL density across the image given the fragility of a gum print.
As often with alt. processes, it's a matter of playing with a bunch of parameters to see if you can find a process window that suits your taste. I'd like to point out that the example prints on the alternativephotography page linked to above are quite pretty, but they're also stylistically fundamentally different from what Calvin made using the process. What makes for an acceptable process window dictates to a large extent what kind of methods and materials are usable.
Elsewhere in his manual Grier mentions that he hasn't found any alternative sensitizer that works well with actual gum printing. The inconsistency with this remark and the page linked to by @revdoc is likely associated with Grier's exacting quality requirements and the particular process he has devised to realize these. For instance, his approach to developing gum prints deviates from the norm - he uses an 'instant' development technique that relies on pH changes. This helps to reduce uncertainty and variation between prints. I'd have to re-read his manual, but I recall this being the cause of DAS not being a suitable candidate for his approach to gum printing. Staining was also an issue, with the permanganate clearing bath likely degrading the gum layer too much. This is also alluded to on the hum diazo printing page where it's stated that prolonged clearance can reduce density in the shadows. I'd wager to say that prolonged permanganate clearing probably reduces ALL density across the image given the fragility of a gum print.
As often with alt. processes, it's a matter of playing with a bunch of parameters to see if you can find a process window that suits your taste. I'd like to point out that the example prints on the alternativephotography page linked to above are quite pretty, but they're also stylistically fundamentally different from what Calvin made using the process. What makes for an acceptable process window dictates to a large extent what kind of methods and materials are usable.
Just to make sure - as I understand - diazo and DAS belong to two different groups of compounds. The latter is di-azido which is -N3 as an end-group while the former has N2, usually in the backbone. They may behave differently in regards to gum. Diazo is easy to get in the form of screenprinting emulsion sensitizer, DAS not so much.
:Niranjan
:Niranjan
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You can use Diazo https://www.laboldtech.eu/prodotto/diazo-4d-5g/ for gum printing see (in German): http://www.edeldruck.org/Edeldruck/DIAZO_fur_Gummidruck.html
bj68
bj68
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