[alt-photo] Re: Alternative sensitiser

[Peter Friderichsen]

Hi Kees,

I use this type of gelatin as I would gum but 
usually I use a 20% wt in solution versus the traditional 30-40% for gum.

That is good to hear that you found an 
alternative to the agar, which looked to be 
somewhat cumbersome. When I free up some time, I 
will want to give your approach a run. These iron 
salts are pretty interesting, some harden, some 
do not, others soften gelatin with light etc... 
yet others harden gelatin with light when 
oxidized. I did come across the Ulano name as 
well under Bernard Ulano of Diagravure film -not 
sure if this is related to the Ulano that you 
mention. Re patents, yes many do not work. I have 
found this out on numerous occasions.

As far as a name to suggest. I tend to be biased 
from the chemistry world which tends more to 
attach names that have some relation to the 
composition,such may be along the lines of 
ferrichrome. I assume the zerochrome name implies 
zero dichromate? I am somewhat indifferent overall.

Peter Friedrichsen

At 04:56 AM 04/16/2010, you wrote:
>Hi Peter,
>
>Interesting results!  Can you tell us how you use the hydrolised gelatin?
>I really think ferric citrate can be a usefull 
>hardener for colloïds. I have been working with 
>Halvor's method (hi Halvor) for Carbon 
>extensively and found a method to make a 
>different protection layer without the 
>agar-agar. I also have found some interesting 
>ferric related patents. Apart from Autoype the 
>Ulano corporation was very active too. That's 
>were Kosar worked, for some time. I found 
>strange patents too! Like the one using 
>plain  ferric chloride as a hardener and ferric 
>citrate as a restrainer. It claimed to speed up 
>sensitivity but allways left me with a chewy 
>lump of pigmented gelatin. A patent is not 
>always  a true working process and often used to 
>mislead others and hide the real stuff.
>
>I earlier suggested zerochrome as a new generic 
>prefix for these processes. Zerochrome-carbon, 
>zerochrome-gum what do you think?
>
>Kees
>
>
>
>
>
>
>On 16 apr 2010, at 05:35, Peter Friderichsen 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
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