U of S | Mailing List Archive | alt-photo-process-l | Re: speaking of gum dichromate

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)