[alt-photo] Re: casein

[Alberto Novo]

Chris, 

> I am finding that the cottage cheese diluted 120ml to 8 oz feels almost like a 14 baume gum, and mixed equally with pot di 10% and 1/4 teaspoon dry pigment, has a nice coating feel, not too thin, not too thick and grabby.

I like these unit conversion problems!!!
Why are you starting with ml and ending with oz?
Let me know if I am reading correctly:
You took 120 ml of cottage cheese and added ammonia up to 8 oz.
8 oz = 236 ml, so that you diluted about 1:1 your cottage cheese.
Diluting 1:1 this with dichromate = 473 ml.
1/4 teaspoon = 1.23 ml, but to convert this into grams one needs the bulk 
density of the pigment. This may vary with the nature of the pigment. I have 
found:
lamp black 100-200 kg/m3 (0.1-0.2 kg/L, g/cc)
raw Sienna 0.6 kg/L
black iron oxide (Mars black) 1 kg/L
burnt Umber 0.7 kg/L
quinacridone red 0.39 g/cc
phthalocyanine blue: 0.45-0.50 g/cc 

Generally speaking, earths and oxides have a bulk density more or less twice 
that of organic pigments. 

So, your 1.23 ml may be from 0.5 to 1.2 g depending on the pigment, and it 
is about 1.25 to 3%, or 0.0125 to 0.03 g/cc in the casein solution. 

When I printed my caseins with red earth, I used:
0.8 g casein + 6.5 ml 15% ammonia + 3.5 ml water: this is about 8% casein 
w/v.
Then I added 0.4 g of red earth for 1 cc of 8% casein solution, plus an 
equal amount of 15% am dichromate. This solution has to be prepared at the 
moment of use (metal oxides, as you know, react with casein).
This is about ten times the concentration of natural pigment / 14 Be gum 
arabic I use (for earths) without flaking. 

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