Re: sizing for gum tests

Hi:

I only let the paper rest for about 24 hours. So its not likely cured
completely. I'll have to leave some of my test pieces for a week and
compare with what I did recently.

Gord

On Tue, 24 Jan 2006, Marek Matusz wrote:

> Gord,
> Did you let the paper rest for a few weeks after siezing to completely cure
> the gelatin? Your observation on gum printing is along my practice as well.
> i can get clear whites at about 6% gelatin, either single or two times 3%
> coat.
> Marek, Houston
>
>
> >From: "Gordon J. Holtslander" <holtsg@duke.usask.ca>
> >Reply-To: alt-photo-process-l@sask.usask.ca
> >To: alt-photo-process-l@sask.usask.ca
> >Subject: Re: sizing for gum tests
> >Date: Tue, 24 Jan 2006 10:42:55 -0600
> >
> >
> >Stonehenge White
> >
> >Gord
> >
> >On Tue, 24 Jan 2006, Katharine Thayer wrote:
> >
> > > Great stuff. What paper are you using, Gord?
> > > Katharine
> > >
> > >
> > > On Jan 24, 2006, at 8:19 AM, Gordon J. Holtslander wrote:
> > >
> > > > Hi:
> > > >
> > > > I continue playing around with sizing techniques for gum.
> > > >
> > > > I haven't been happy with tray sizing - my results have been
> > > > inconsistent
> > > > so I've been playing with brush sizing - actually roller sizing.
> > > >
> > > > I've been applying the size with a foam roller with a fine nap finish.
> > > > The roller leaves small bubbles, so I finish the size with a paint
> > > > pad - a
> > > > 7 inch wide pad. The pad has a fine layer of bristles on a 1/4 thick
> > > > piece of foam. Produces a nice even coat.
> > > >
> > > > I use chrome alum as a hardener and add it to make a concentration
> > > > of 0.5%
> > > > of the size mixture.
> > > >
> > > > I decided to be more scientific and introduce only one variable at
> > > > a time.
> > > >
> > > > I tried three sizes techniques, single coat gelatin, double coat
> > > > gelatin
> > > > and single coat casein. Gelatin was mixed one envelope of plain
> > > > knox food
> > > > grade in 250 ml water, left to sit for 1/2 hour heated to 50 C and
> > > > then
> > > > add chrome alum.
> > > >
> > > > The casien - I put 30 g of scientific grade powdered casein in 300 ml
> > > > water, add 100 ml ammonia (household grade), and chrome alum (at 0.5%)
> > > >
> > > > Double coat gelatin - I applied gelatin, let it dry for an hour, and
> > > > applied another layer. Single coat gelatin and caesin - applied a
> > > > single
> > > > layer and dried.
> > > >
> > > > I coated one small sheet of each with the same gum/dichromate/
> > > > pigment mix.
> > > > Exposed to a test negative and a stouffer 21 step tablet, at the same
> > > > exposure time.
> > > >
> > > > The double coated gelatin gave the best results, clear highlights and
> > > > prints 9 distinct steps on a stouffer 21 step tablet
> > > >
> > > > single coat gelatin produced mottled highlights. The gradation
> > > > between
> > > > the steps was very different compared to the double coat gelatin. The
> > > > difference between the steps is not pronounced. The single coat
> > > > gelatin
> > > > size produces a much more contrasty image. Almost no detail in the
> > > > darker
> > > > regions compared to the double coat gelatin. Hard to see a
> > > > differnce in
> > > > the steps. Prints a very short tonal range.
> > > >
> > > > The single coat casein size, produced results very similar to
> > > > single coat
> > > > gelatin, but it produced a denser black, and somewhat more detail
> > > > in the
> > > > highlights, but still had mottled highlights. Contrast appears to be
> > > > better than single coat gelatin, but not as good as double coat
> > > > gelatin.
> > > > Looks like casein sizing might support an image with a longer tonal
> > > > scale.
> > > >
> > > >
> > > > Will try a double coat casein size and see how it compares to
> > > > double coat
> > > > gelatin size.
> > > >
> > > > Gord
> > > >
> > > > ---------------------------------------------------------
> > > > Gordon J. Holtslander Dept. of Biology
> > > > holtsg@duke.usask.ca 112 Science Place
> > > > http://duke.usask.ca/~holtsg University of Saskatchewan
> > > > Tel (306) 966-4433 Saskatoon, Saskatchewan
> > > > Fax (306) 966-4461 Canada S7N 5E2
> > > > ---------------------------------------------------------
> > > >
> > >
> >
> >---------------------------------------------------------
> >Gordon J. Holtslander Dept. of Biology
> >holtsg@duke.usask.ca 112 Science Place
> >http://duke.usask.ca/~holtsg University of Saskatchewan
> >Tel (306) 966-4433 Saskatoon, Saskatchewan
> >Fax (306) 966-4461 Canada S7N 5E2
> >---------------------------------------------------------
>
>

---------------------------------------------------------
Gordon J. Holtslander Dept. of Biology
holtsg@duke.usask.ca 112 Science Place
http://duke.usask.ca/~holtsg University of Saskatchewan
Tel (306) 966-4433 Saskatoon, Saskatchewan
Fax (306) 966-4461 Canada S7N 5E2
---------------------------------------------------------
Received on Tue Jan 24 14:24:36 2006