Re: sizing for gum tests

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
>---------------------------------------------------------
Received on Tue Jan 24 14:04:31 2006