Re: Casein -> it's the paint

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

Hi all,

I tried with powdered pigment and this time (3rd trial) got an image. So,
(for the moment) I conclude that the reason of not getting an image in the
first try was the acrylic paint. The 2nd was made w/ the same emulsion but
this time by putting a little of ammonia in the development water (by
suggestion of a list member), it was better compared to the first time
(reacted to force development) but nothing near to usable / successful.

I'm making these tests on plain Yupo paper. And casein is much much better
in adhering to the paper -> in all my trials with gum on plain Yupo, the
emulsion had left the paper completely...

A side note: I got tonal reversal with the 3rd trial -> it was a very dark
/ contrasty mix exposed only 1 minute under UVBL (2 parts casein/pigment +
1 part 5% AD).

Regards,
Loris.


22 Mayıs 2009, Cuma, 10:06 pm tarihinde, Loris Medici yazmış:
> I did my first casein trial yesterday evening, w/o any success. See below:
>
> - 0.8g casein (Kremer's)
> - 5ml tap water
> - waited 10 minutes (to let casein absorb water - I'm not sure if that's
> necessary but did so anyway, I was not in a hurry...)
> - added 8 drops of 25% (910) ammonia (it seems to be a lot, will try
> halving the amnt. next time)
> - I mixed the slurry (cream consistency) until it looks homogeneous
> - I added 5ml of 5% ammonium dichromate (it turned to yellow - because of
> excess alkalinity I presume...)
> - I mixed the solution (not a slurry anymore, pretty homogeneous looking
> solution slightly less viscous than my usual gum coating mix)
> - made up a coating solution by adding the dichromated casein solution to
> a very small amnt. of W&N acrylic color (burnt umber)
> - coated the paper, dried with a hair dryer, humidified the paper with an
> ultrasonic humidifier, exposed for 2 mins. under a bank of UVBL tubes (I
> didn't get a dichromate image after exposure)
> - developed(!) face down for 20minutes
>
> I got absolutely no development, no pigment coming off, no dissolution of
> binder at all.
>
> What could be the cause?
>
> Overexposure? Using acrylics? (But I know someone - Guido Ceuppens - who
> uses acrylic colors with casein...) Both? Any other thoughts?
>
> Will try with only 30secs exposure tonight...
>
> Regards & thanks in advance,
> Loris.
>
>