RE: alternative to dichromate sensitizer

From: SitgesN1@netscape.net
Date: 01/20/05-05:41:04 AM Z
Message-id: <60E529B6.5A9BB068.0082BC06@netscape.net>

Tom,
I fully agree with you concerning dichromates are very dangerous.
Sometimes daily use of this product can induce us to believe it is
not so, but if anyone have some doubts please go to:

http://cavemanchemistry.com/oldcave/projects/photo/AMMONIUM_DICHROMATE.MSDS

I believe that after more than 100 years using it we should try to
find a better substitute for this nasty product.
During more than 3 months I've been trying to find it for tricolor gum/tempera and carbon processes and although I must confess I had no succes yet I'm convinced solution is not very far. Maybe combining knowledges of this community we could arrive to get some interesting resultsí.
Due to my profesional life -I'm an electronic engineer- I know dichromates were used in the early times as sensitizers for preparing negative photoresist - this is how electronic industry calls for the combination of gum+sensitizer- for making printed circuits boards. Later during the 60s Kodak combined cinnamic acid with polyvynil alcohol and this negative
photoresist was very popular and known as KPR. Later on the positive photoresist was born due to the combination of Novolak resin plus DNQ -diazonaphtoquinone- Positive photoresist represented an improvement and produces very accurate images and its coating thickeness is not as critical as negative resist. For those interested in knowing a little bit about the principles of these types of resist and how to apply the coatings I suggest to read:

http://www.htp.ch/lib/pdf/Liquid%20resist%20for%20PCM.pdf
http://www.ee.washington.edu/research/microtech/cam/PROCESSES/PDF%20FILES/PhotoresistPos.pdf

I believe should be very interesting to find a positive photoresist for improving gum/tempera and carbon printing processes.
If any one should be interested in this project I would be delighted to interchange ideas and findings about it.
-Francesc
   
>Hello all,
>
>One of the things that bothers me most about old photo processes is the
>use of dichromate. Toxic, carcinogenic, environmentally harmful. All in
>all, not a nice ion to work with.
>
>A few years ago, I looked into the UltraStable color process (Berger,
>California, if I remember correctly). They seem to use some organic
>sensitizer instead (but still with gelatin emulsions as far as I can
>tell). Setting up an UltraStable lab turned out to be too expensive for
>me, so further inquiries stopped.
>
>I would very much like to use something safer than dichromate (for
>carbon, gum and possibly temperaprint). Does anyone on the list know
>what sensitizer is used for the UltraStable process. I can't find
>UltraStable on the web, so I have not asked them directly (I don't even
>know if they are in business). They may consider it a trade secret, but
>I hope not.
>Alternatively: Does anyone know suitable candidate sensitizers that
>could replace dichromate?
>
>
>Best regards,
>
>Tom Einar Andersen
>
>

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Received on Thu Jan 20 05:41:34 2005

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