[alt-photo] Re: casein+ alt to dichromate

[Peter Friedrichsen]

Kees,

Looks like you got it all to work. Congrats on that.

The one other thing to watch out for is how you drop the print into 
the peroxide-water development bath. If you partially submerge it for 
even a second, and then continue to submerge the rest of the print, 
an undeveloped line will appear at the location where the print was 
partially submerged, so you have to  drop the whole print into it in 
one step. Not sure of the cause. Perhaps the paper fibers act to 
separate the peroxide from the water. Nonetheless it quickly becomes 
second nature to do it quickly.

Your suggestion that gum is too slow to react perhaps is the problem. 
I think that something in the gum may be robbing the oxygen from the 
peroxide initially -an antioxidant effect, but that is really only speculation.

Peter Friedrichsen


At 11:52 AM 20/06/2012, you wrote:
>I have been printing a lot of ferric carbon and also another 
>non-dichromate (read: less toxic) method. Second one based on 
>diazidostibene as the hardening agent. This was the magic potion 
>used in the (legendary) ultrastable tissue.
>Both (ferric and diazidostilbene) make it possible to make 
>presensitized tissue because of the absence of a dark effect.
>
>But today I tried the ferric casein method! I never had printed 
>casein before but got inspired by the recent casein thread and 
>Peter's post. And the results were amazingly good!
>
>This is what I did:
>
>I bought a package of cottage cheese and sqeezed it in a fold of 
>tissue to let it loose it's liquid. The resulting still humid mass 
>was 65 gr. I crumbled it and added 50ml household ammonia (<5%) and 
>let it stand some hours. This was too much ammonia I think because 
>the pH was way too high. I added 2 teaspoons of citric acid powder 
>to lower it to pH 6 and helped with a mixer to make a nice smooth colloid.
>
>Then I took my allready available classic cyanotype A solution (20%) 
>and measured it's pH which was around 4.5. I added 10 ml household 
>ammonia to set the pH to 6.
>
>Then I took an equal part of this pH adjusted cyano A solution and 
>the casein solution. From this mix I took 20ml and added 1gr. 
>lampblack aquarel paint.
>
>This was coated on a gelating/glut sized piece of paper and dried. 
>Coating is similar to gum.
>When dry I exposed it 7 min, my regular time for cyanotype which was 
>an excellent guess.
>After exposure the print went in a 0,3% peroxide bath were some real 
>magic happens!
>
>This is were things go wrong with ferric gum, because gum is much 
>more soluble then casein. With gum the peroxide doesn't have the 
>time to do it's work. With casein there is just enough time to let 
>it finish the hardening just before the development starts. Very nice!
>Also development is very fast, after 3 minutes in the perioxide I 
>transfered it to another water bath and moved the print a bit in the 
>water for 5 minutes. Ready!
>
>This is by far the easiest ferric pigment printing technique, and 
>maybe also the easiest gum/casein approach.
>
>Try it!
>
>Kees
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