[alt-photo] Re: Alternative sensitiser

[Peter Friderichsen]

Sam,

I have made some "gum" prints sensitized with ferric ammonium 
citrate. Use those quotes because in actual fact I have used casein, 
and previously gelatine that I modified to remain liquid at room 
temperature, although I am now working mostly with casein because it 
has such excellent clearing and can manage a  high pigment load, 
although it has its own temperaments as well. I have a few of these 
scanned and have posted them at 
http://picasaweb.google.ca/pgfriedrichsen/AlternativePrints#

Essentially the sensitizer is mixed in as you would dichromate. 
Exposure time is equivalent to gum dichromate. The print must then be 
immersed in a dilute solution of hydrogen peroxide (0.1%) is 
sufficient. (Oddly, this system does not work with Gum arabic) I then 
flow water over the print for about 1 minute and then hang it to dry. 
Dynamic range is about 5-8 steps on a 21 step stouffer wedge. That is it.

If anyone wants to go this route, be prepared to spend a lot of time 
figuring things out because there really is little literature to go 
by with the exception of a study done by Halvor Bjoerngaard of Chiba 
University, and it is quite informative. He coined it The Chiba 
system although it was suggested more than 50 years ago, and the 
Autotype company had a patent for this approach for use in making 
photographic stencils back in 1952.

This low toxicity system is what I now use pretty well exclusively, 
and I believe it is capable of producing excellent results, just not 
right out of the box.

Peter Friedrichsen


At 08:31 PM 04/15/2010, you wrote:
>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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