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

[Peter Friedrichsen]

One other benefit of using casein that I know of although it is not 
directly related these printing benefits below is that the dichromate 
can be replaced with an iron-based sensitizer eliminating the risks 
of dichromate use. This may be a useful alternative if you can't get 
dichromate or don't want to use it. I mentioned this once before but 
Ill mention it again, even with the risk of being redundant since 
this casein topic is receiving so much attention.

In essence, you simply have to make your ammonium caseinate by 
precipitation with a minimum of ammonia ( or sodium hydroxide, 
carbonate, bicarbonate) to maintain a pH of less than 7 which is ok 
because casinates form a stable emulsion down to around pH 6. The 
reason being that iron sensitizers such as ferric ammonium citrate 
(FAC), or ferric ammonium oxalate (FAO) won't work in an alkaline 
environment unlike the powerful and tolerant dichromates. You must 
also alkalize your FAC or FAO with an excess of ammonia to gets it's 
pH up to about 6 or 6.5, otherwise its natural lower pH will 
coagulate your emulsion much like vinegar does to milk. The last 
inconvenience of this system is that the print must be developed in 
water-hydrogen peroxide but even a dilute solution of 0.1% is 
sufficient. I find FAC to produce a finer grain and longer scale and 
it has much less of a tendency to leave iron behind although this can 
be removed with a mildly acidic rinse.

You can find more info on this approach if you read the Chiba system 
paper by Halvor Bjoerngaard  however Halvor did not work with casein, 
but the principals are there.

Peter Friedrichsen



At 08:09 PM 18/06/2012, you wrote:
>Hi Kurt,
>
>Casein is replacing gum in my testing.
>
>There are benefits to casein. Will it replace my gum practice as my 
>process of choice, no. But here are some advantages off the top of my head.
>
>Cheap and easy.
>
>Little dichromate.
>
>Grain is verrrrry fine.
>
>No gloss at all with powdered pigments.
>
>Exposure is quick, as little as 15 seconds to no longer than 4 
>minutes in my practice.
>
>Development is quick, as little as instantly to 15 minutes.
>
>Colloid is tenacious as hell. Can be printed on plastic easily.
>
>Colloid holds a HUGE pigment load.
>
>Flaking pretty much non-existent.
>
>Chris
>
>Christina Z. Anderson
>christinaZanderson.com
>
>On Jun 18, 2012, at 2:38 PM, Kurt Nagy wrote:
>
> > I havent really been following this thread too close but I'm 
> confused on the reasons for casein and all this cottage cheese talk.
> >
> > Are you using the casein as a size or is it replacing the gum bichromate?
> >
> > What is the benefit of this vs Gum?  Are the prints smoother or 
> clear easier?
> >
> >
> >
> > On Jun 18, 2012, at 10:32 AM, Christina Anderson 
> <zphoto at montana.net> wrote:
> >
> >> Alberto et al,
> >>
> >> Oh my, now i hate to tell you that not even those are necessary 
> anymore so I'm glad you and Bob and Mark like it :0. Now I'll just 
> have to rinse them and wear them (NOT!!!).
> >>
> >> Last night I just took some nonfat cottage cheese and put it in 
> a kitchen strainer, rinsed off the liquid in about 30 seconds, 
> measured it, weighed it, liquified it in ammonia in an hour and it 
> was ready to go.
> >>
> >> I also tried it unrinsed, just as is. I notice an interesting 
> thing. When the ammonia is added, the little curds turn clear like 
> tapioca in pudding pretty instantly, but the white stuff 
> surrounding cottage cheese stays white. Hence the next test I 
> rinsed. Today the unrinsed remains white and the rinsed looks just 
> like the casein that you buy from Kremer.
> >>
> >> I also scrupulously measured and weighed everything by weight 
> and volume and came up with (how clear is this, Paul!!!)  a 12% 
> solution using your and Peter's .23 calculation of pure casein in the mix.
> >>
> >> With the fact that cottage cheese is already separated into 
> curds for you, to me there is not much reason to do skim milk or 
> any other method aside from using casein powder. It was a complete 
> no-brainer, ready to use in an hour with a nice pure casein. For a 
> beginner anyway, not knowledgeable about the nuances of different 
> brands of cottage cheese.
> >>
> >> Off to Rochester for research tomorrow AM....
> >> Chris
> >>
> >> Christina Z. Anderson
> >> christinaZanderson.com
> >>
> >> On Jun 16, 2012, at 1:40 PM, Alberto Novo wrote:
> >>
> >>> Those plastic glasses wearing stockings are very sexy indeed :-)
> >>> Alberto
> >>> www.grupponamias.com
> >>> www.alternativephotography.com/wp/photographers/rodolfo-namias-group
> >>> _______________________________________________
> >>> Alt-photo-process-list | http://altphotolist.org/listinfo
> >>
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