[Alt-photo] Re: casein on glass

[Jorj Bauer]

> now it's the immense task to find the proper PS-curve, On Jalo's book, there's one picture of tens of ChartThrob prints hanging drying.

I know the feeling. I've got piles of them too.

Maybe this will help you: I dug up my notes for She Drank a Little Whiskey.

The glass is prepped with a scrub of barkeeper's friend (later prints had very little to no glass prep; I found it unnecessary, except to remove the tape residue from its packaging).

I'm printing the negs with epson inks on a Stylus Pro 4000, and I found that cyan is particularly good at blocking the right UV wavelength for casein prints, so there's an overlay of RGB 88/76/00. The negatives are also printed with a border; trimming them to that border yields a neg that lines up with the edges of the glass. That's how I register on glass; to the edges of the pane. Of course since I'm printing on multiple panes of glass, I then register the panes with each other when they're set in the final frame.

I put a scaled-down version of the photoshop document here, which might be useful to see what I meant by all of that:

	http://www.jorj.org/expire/whiskey-negs.psd

and just the curve, which I also use for 5 minute casein exposures on Fabriano Artistico, here:

	http://www.jorj.org/expire/jorj_887600_casein_5m_fabart.acv


I used Schmincke pigments, ~0.3g, with 3ml of 10% ammonium caseinate and 3ml of ~13% (saturated) potassium dichromate, reheated to get it back in solution (the ambient temperature was probably 50F/10C). That covered two 8x10 panes of glass; I like to print at least two at once.

I noted that 0.5g of pigment was too much and caused flaking while soaking in water.

Potassium dichromate was an important part of the process. I noted a lot of failures using ammonium dichromate. I'm sure one could make AmDi work just fine with enough work. I didn't put in too much effort.

My casein stock is dry casein powder, used for milk paints. It's much easier to work with than milk, and stores a lot better :) 500g of "Ultra Casein Powder" from earthpigments.com, looks to be a 5-year supply for me.

Brushed 3ml on to an 8"x10" pane of glass, edge-to-edge, over a 5-minute period. Not brushed continuously; I let it rest for ~30 seconds between brushings at first, and gave it more regular brushings as it approached dry (over about 10 minutes). Dried ~30 minutes longer in a drying cabinet.

Exposures are between 6 and 7.5 minutes; it looks like my starting point was 7.5, and some layers/negatives pushed me down as low as 6. (Homemade UV BL exposure unit, about 6" away from the vacuum frame.)

The casein stuck firmly to the sheets of glass, which cleared in about 90 seconds of cold water soak.


-- Jorj