[alt-photo] Re: Alternative sensitiser

[sam wang]

Hello Peter,

Great to know that and to see your casein prints!

Many years ago I learned casein from Franklin Enos, who till now was the
only original source for the process that I know of. Franklin did a lot of
original research in the 50's while he was vice president of French's, and
had a copy of a patent but unfortunately I did not record the number.
Perhaps that was the Autotype patent? Would you by chance have a copy or
details about it?

Your method of using ferric ammonium citrate and hydrogen peroxide is very
interesting. I was using dichromate and a dilute solution of ammonia. I had
a hard time finding paper that allowed multiple printing without staining.
Obviously that's not the case with your method. I would be very interested
if you care to elaborate it further.

Thanks, Peter, for sharing!

Sam Wang

On Fri, Apr 16, 2010 at 11:35 AM, Peter Friderichsen <
pfriedrichsen at sympatico.ca> wrote:

> 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
>
>