[alt-photo] Casein notes

[Alberto Novo]

OK, I have looked into my 2007 notes on casein.
First of all, I have to mention 1908 A. J. Boult patent n. 19,297 "Improved 
process for manufacturing Pigment pictures" where he writes: "Many attempts 
have been made to use casein in combination with chromatres as a binding 
medium for manufacturing pigment pictures. Those methods were not, however, 
of practical value, chiefly because the compounds of casein with chromates 
after the drying of the layers, could be dissolved only with difficulty, 
namely in strong alkalis such as ammonia, even when the chromate was not 
reduced by light." His method is an application of Manly's patent on 
ozobrom. 

At that time, I found five different recipes for casein printing. Some use 
powdered milk, other casein.
 From my measurements on the casein yield from a sample of powdered milk, I 
can say that those five recipes use solutions of casein ranging from 4% to 
16%.
The recipes were coming from:
 - Ernest J. Theisen in http://unblinkingeye.com/Articles/Casein/casein.html
This is perhaps the older article.
 - Bob Schramm in www.usask.ca/lists/alt-photo-process/alt95/0831.html
His recipe has been described by Laura Blacklow in 
www.alternativephotography.com/wp/processes/gum-bichromates/casein-pigment-p 
rints
 - Alternative Photographic Processes by Webb & Reed
 - Lukas Werth in his website (not active anymore) and in Post Factory 
Journal #6
 - Charlie Bagget in www.usask.ca/lists/alt-photo-process/2002/apr02/0546.htm 

In addidion, there are many patens on casein bichromate used as a resist for 
etching metal sheets in the production of TV color screens, because its 
insolubility in acids. The best examples are US pat. 4,230,781 (1980) and 
4,865,953 (1989), the first using borax to dissolve casein, the second 
sodium hydrate. There is also the Japanese patent n. 169,720 (2007) using 
ammonia. Unfortunately, it is written in japanese but from the abstract "the 
photoresist is composed of casein, ammonium dichromate and ammonia water", 
and its pH is "7.45+-0.15". 

For the preparation of the casein solution, I have used a 150 cc jar with a 
screw cap, placing inside 0.8 g of casein powder (recipe #4). Then I spray 
10 cc of 9.5% ammonia by means of a syringe aiming to disperse it at best. I 
put the well closed jar in a water bath at 60°C for 15', gently stirring it 
some times, then I chill it in cold water and the solution is ready for use. 
I have noticed no difference between the fresh prepared casein solution and 
that stored in the refrigerator for a week. However, preparing what is 
needed every time is not so time consuming, so I didn't store it. 

Oh, about the amount of pigment, I have found possible to use up to ten 
times of pigment compared to gum. But in this case the development needs 
some ammonia in the water and some mechanical help on its surface. 

Alberto
www.grupponamias.com
www.alternativephotography.com/wp/photographers/rodolfo-namias-group