[alt-photo] Re: Alternative sensitiser

[sitgesn1 at aim.com]

 Some years ago I was very interested in finding a positive photoresist as a substitute of dichromate for carbon printing without transfer. While reading "The Silver Sunbeam" book by Towler, at page 285, I realized positive photoresist designed by Poitevin was ,in principle, suitable for my purpose. I was very captivated by this process but unfortunately I never could, for non photographic reasons,  checked it . For those interested in this process I reprint from the book:

"Printing directly on paper by means of the sesquichloride of iron and tartaric acid"
-Five or six parts of gelatine are dissolved in 100 parts of water. This solution is colored with lampblack  or any other inert color. Each sheet of paper is floated on this solution which is kept lukewarm on a water bath. With the colored side uppermost let paper dry on a horizontal surface.
-In order to sensitize immerse the paper in a bath containing a solution of  10 parts of sesquichloride of iron,  100 parts of water and 3 parts of tartaric acid. Let the paper dry in the dark. The film of gelatine has become completely insoluble even in boiling water
The film receive actinic impressions through a transparent positive and in the part where the light acts the film becomes soluble in hot water  proceeding from the surface of the film in contact with the transparent positive.
After exposure the paper is immersed in hot water and all the parts that have undergone the solar influence are dissolved in proportion to the quantity of light received...
To finish the print allow it to dry and then wash in acidulated water in order to get rid of salts of iron"

Regards
-Francesc


 


 

 

-----Original Message-----
From: sam wang <samwang864 at gmail.com>
To: The alternative photographic processes mailing list <alt-photo-process-list at lists.altphotolist.org>
Sent: Fri, Apr 16, 2010 2:31 am
Subject: [alt-photo] Alternative sensitiser


Has anyone tried using some sensitisers other than dichromate for gum or
carbon? Silkscreen emulsions have used diazo since the 70's. Can it be used
for our purposes? If so, would it be less toxic, and would longevity of the
emulsion be increased?

A somewhat related question: does anyone know the chemical make-up of
KwikPrint? It was popular in the 70's to the 80's. First made for proofing
print jobs and them sold by Light Impressions for alt printing. Best results
when used on a king of vinyl that comes with it. Are there no old timers on
the list who can shed light on it? Seems that it was akin to casein and used
diazo as well.

Sam Wang
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