[alt-photo] Re: casein

[Christina Anderson]

Yup, same amount of pigment. I think I remember you or Peter Blackburn saying this in one of your emails and was very surprised, so that's why I took my findings with a grain of salt, until someone else said it was short (Don or Marek). But until I do both gum and casein together on the same day and same pigment dilution and compare I won't stick to my opinion. When I do that, I will post the two step wedges together.

I could not use the same curve I use for gum and had to go and develop a whole new set of curves for casein. Casein blocks up in the very deepest shadows right before black, and I find that it needs a slight increase in contrast in the deepest shadows in all three colors. Plus my curves for magenta and thalo, which are similar enough in gum to be interchangeable, are not in magenta and thalo in casein. Don, let me know when you calibrate casein what your curve looks like, too, if you find this to be the case. My curves are very odd.

The other thing I noticed is the slight opacity to casein makes the shadows look a bit streaky, like if one were to use a cadmium yellow pigment as a last layer in gum on top of darker colors.

I just got back from South Carolina where I was doing a gum workshop with the Fine Arts Center--calibrating the SUN and with no true contact printing frames, so everywhere I do a workshop there are challenges :) but I was able to spend some time with Sandy King and Sam and used Sam's Amergraph to expose a casein layer. So my next step is to use my Amergraph to see how that type light has an effect as well--what is it, mercury xenon?? Can't remember.

And, down there we were using a 5% pot di, Don, with a 220 unit (?) exposure and that seemed plenty. I was still able to wipe off pigment with hard scrubbing in all but the deepest shadows (just one of the silly tests I do, to see how responsive a layer is to complete removal).
Chris


Christina Z. Anderson
christinaZanderson.com

On May 2, 2011, at 3:26 AM, Alberto Novo wrote:

>> ... But I do find casein shorter scale on a Stouffers--gum about 4-6 stops (usually 5.5) and casein about 3.
> 
> Mixing the same amount of pigment? My first experience was the contrary, that is a longer scale with casein. 
> Alberto
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