Re: speaking of gum dichromate
Hi all Some more info on Halvor Bjørngård's Chiba system is here: http://photorelief.googlepages.com/thechibasystem Halvor describes the colloid hardening properties of FerricAmmoniumCitrate (!) for carbon transfer and direct carbon. Its a must read for all dichromate users! I have been testing the gelatin variant of his direct carbon method. It's a very interesting and working approach! A warm pigmented gelatin is sensitized with Ferricammoniumcitrate and coated very thin, like gum, on paper. After exposure the paper is put in a very dilute peroxide bath for 5 seconds to get the hardening reaction. After that the non-hardened gelatin is removed in a 'cabon' way in warm water (38 degrees). Like gum printing several layers adds density. pro's: -no dichromates, safer and cleaner printing! -no dark effect, no hardened size needed con's; -warm pigmented gelatin is very difficult to coat thinly whithout streaks -a nonhardened sizing is needed before each layer but gum can also be used in stead of gelating -it is not working with gum, it would wash off in the peroxide befor hardening. A workaraud is also in the thesis but at the cost of a dark effect. I will continue to experiment. Next step will be coating with a threaded rod instead of a brush. kees http://polychrome.nl On 15 jun 2008, at 22:22, Ryuji Suzuki wrote: I always meant to post this note to this list but I think I forgot for a year. An article entitled "Chiba Type --- A non-toxic alternative to gum dichromate" by Halvor Bjørngård and Hiroyuki Kobayashi was published in Journal of the Society of Photographic Science and Technology of Japan, volume 70, pages 102-112. I think this is a part of his thesis work at Chiba University. Abstract is in English and Japanese, but the text is in English. I only have a bound journal and they don't post electronic version so I don't have anything I can paste here (besides the copyright issue), but if anyone is seriously interested, please let me know privately. -- Ryuji Suzuki "The truth that I am seeking is in your missing file." (Bob Dylan, Something's Burning Baby, 1985)
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