[alt-photo] Re: casein history

[Peter Friedrichsen]

Marek,

I have never found the high ph to have negative effect on light 
sensitivity but only dark reaction. I also read somewhere and I don't 
recall where or who it was, but the author suggested ammoniating 
ammonium dichromate to reduce the hardening rate of this when mixed 
with a colloid for short term storage; it may have been gum or gelatine.

Peter Friedrichsen

At 10:50 AM 14/07/2012, you wrote:

>Peter, It is definitely true that dichromates become chromates at 
>high pH. I had an impression that chromates are more light sensitive 
>then dichromates and that the old recipies had ammonia as one of the 
>components to increase light sensitivity, but I could very well be 
>mistaken. Since my casein solutions contain ammonium carbonate they 
>do bubble happily when mixed with potassium dichromate. Marek
>  > Date: Fri, 13 Jul 2012 21:25:15 -0400
> > To: alt-photo-process-list at lists.altphotolist.org
> > From: pfriedrichsen at sympatico.ca
> > Subject: [alt-photo] Re: casein history
> >
> > Marek,
> >
> >  From what I understand, the dichromates shift to chromates as they
> > are made more alkaline (from your ammonia) and these salts are less
> > reactive especially in the higher pH. That may explain the lessened
> > dark reaction.
> >
> > Peter Friedrichsen
> >
> >
> > At 12:58 PM 13/07/2012, you wrote:
> >
> > >Chris,I have not tried this approach yet, my bag of sawdust went
> > >missing. On the other hand I have been making some prints, mostly
> > >monochrome for about a year now. I have also made some prints from
> > >the one year old casein solutiojn, actually it was more then a year
> > >old. Works just fine. It is interesting that the first solution that
> > >I ever made turned to be the best recipe.Another interesting tidbit
> > >is that I have exposed and developed one day old paper checking for
> > >the signs of dark reaction and found none. There is one more piece
> > >from that batch that I will let sit for perhaps another day or two
> > >before exposing and developing. As to your other questions I read
> > >the PF article years back, but did not think of it much at the time
> > >(in terms of my own interest). I only got interested in it last year
> > >with the posts on the list.
> > >
> > > >
> > > > Also, Marek, you were talking about Fresson maybe containing
> > > casein. The amount of casein/gelatin I have come across is 10-30%
> > > casein to gelatin. Have you tried it yet?
> > > >
> > > > Chris
> > > >
> > > > Christina Z. Anderson
> > > > christinaZanderson.com
> > > >
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