Casein notes

[Loris Medici <mail@loris.medici.name>]

Hi all,

Just started to get something close to usable with Casein. See below:

1. Speed is incredible; my standard exposure time is below 1 minute, norm
being something like 45 secs with 5% AD. (Coating solution: 1 part
casein/pigment + 1 part dichromate, casein solution strenght is 8% w/v.)
This is for a pigment strength which will give convincing blacks with only
2 - or maybe 3 - printings. (Sensitizer will definitely handle more
pigment w/o any problems; I had absolutely no flaking when experimenting
with much stronger pigment strenghts...)

2. There's considerable veiling of highlights but not exactly the
"staining" we experience in gum, it's different. I'm currently
experimenting with 3% gelatin sized (hardened w/ formalin) paper. Will try
to increase the sizing strenght to 6% or even 9-10% and see what happens.
I use powdered pigment (Schmincke Graphite) for the first time; maybe it's
due the pigment??? Will also see if it's acting the same way with tube
watercolor pigments.

3. Casein needs a different negative compared to cyanotype and gum. (I use
the same negative - color and curve - for both 2A:1B cyanotype and gum.)
My shadows block (highlights are OK), whereas I have good shadow detail
when using the same negative for both gum and cyanotype.

4. Development is as following: I put exposed paper in room temperature
water for 10 minutes letting the dichromate leach out and the coating
solution swell. Very little pigment comes off, only the specular specular
highlights. Then, I put the paper face down in a very weak ammonia
solution (I mean "weak" here -> 3ml 25% ammonia per 2000ml water), the
image develops completely within 15 - 20 minutes. I can expose more and
try force development too; will makem further experiments on that
direction too. (3 minutes exposure is more than enough to make a very
robust layer which will only develop - still with blocked shadows - by
pouring relatively high pressure water over the paper with a shower
armature!)

That's all for now, please comment if you have someting to add/share in
that matter.

Regards,
Loris.