Humidity

Just a quick note about the effect of humidity: the negative that I used
for the test prints I did this morning is a 4x5 film negative that
usually prints perfectly in 1 to 1.5 minute on a gelatin or gel-gesso
size, in my normally very humid climate. We're having a dry spell; I
printed all of these at 5 minutes and I think it's clear that the one on
gel size, at least, was underexposed. Just another example of the
effects of the vertical relationship between speed and humidity. More
about this later,
Katharine

Katharine Thayer wrote:
>
> Judy Seigel wrote:
> >
>
> > When I began testing for gum (more years ago than I have actually been
> > alive) it was popular in the (then) new manuals to suggest dilute acrylic
> > medium or dilute acrylic gesso (liquitex) as substitute for the gelatin
> > size - as being much quicker and easier.
> >
> > When I tested with a 21-step I found that as size *for gum printing* none
> > of them in any dilution worked as well as gelatin for paper size -- for
> > continuous tone.
> >
> > They simply did NOT do smooth highlights AT ALL.
>
> Hi All,
> This morning I've printed test prints and 21-steps on the following
> sizings on Arches Bright White paper: (1) PVA-glue 1:10 (2) gloss
> acrylic medium 1:10, and (3) gelatin with glyoxal, with the following
> results (with a continuous tone negative and the same coating mix, a
> rather heavily-pigmented greenish black, and same exposure for all):
>
> The gelatin-glyoxal gave the smoothest gradations, but the fewest tones
> (5); it was very smooth but very high-contrast, with few midtones and no
> highlight tones at all.
>
> The PVA gave a few more tones than the gelatin, but there was serious
> mottling in the shadow areas of the gum.
>
> The acrylic medium printed all the tones in the negative, from shadows
> to highlights; the gradations were a bit less smooth than the gradations
> on gelatin, but the print overall *looked* better because it was a fully
> tonal print. The 21-steps show no relation to the actual print, which is
> why I don't use step wedges to determine anything about printing.
>
> These are all still wet but if I have time this afternoon I'll scan them
> after they are dry.
>
> Katharine
Received on Fri Aug 5 12:33:03 2005