[alt-photo] Re: Alternative sensitiser

[halvor]

Hi Kees ++ : -)

I "am here" still, but only read the list occasionally. Unfortunately I
have not had much time to do any printing the last years, or if time - no
money to do anything which is the current situation ..(anyone know of an
alt p job in Tokyo? : -) 

zerochrome sounds good : -) I got hold of the chemicals for your method,
but have not been able to test it yet, it does seems very promising though.
If one can avoid the agar layer things do become a lot easier ...

as I am not printing at the moment it is a bit difficult to comment too
much here, but just quick -  (Peter) ferric "works" for gum arabic, but the
method is very unreliable and the result not good compared with normal
"chromed gum" (there is a strong dark reaction and the hardened gum is not
all that strong, but I have seen the odd image on-line made that way) ...,
however I did not manage to make it work with casein, obviously a question
of experience with the material  : -) (so it is nice to hear that it is
possible).

else regarding next mail in this thread (Francesc)

http://halvor.deviantart.com/art/Sesquichloride-of-Iron-33790868

a while since I did that test, but the ferric chloride method - positive
working, this with gelatin. Very low sensitivity, and unsharp in
"highlights" for thicker layers (which was my focus then) but easy to do, I
only did some tests but it looked promising.

Halvor


On Fri, 16 Apr 2010 10:56:06 +0200, Kees Brandenburg
<workshops at polychrome.nl> 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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