[alt-photo] Re: casein

[Paul Viapiano]

That's not the way I read it at all...I naturally figured it was 8 oz of cottage cheese to 120ml of ammonia. Why would you measure a solid in ml?

But stranger things have been seen here ;-))

P

On Jun 15, 2012, at 9:26 AM, "Alberto Novo" <alt.list at albertonovo.it> wrote:

> 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
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