Re: son of a gum tonal inversion test

From: Joe Smigiel ^lt;jsmigiel@kvcc.edu>
Date: 12/06/05-02:11:25 PM Z
Message-id: <s395aa35.033@gwgate.kvcc.edu>

Some more scans of the gum tests of previous days now showing effects of
 clearing for 5 minutes in fresh 5% sodium metabisulfite solution. The
clearing solution has shifted the color of the chromium image from tan
to pale green (trivalent chromium now???) and lightened it a bit. The
dichromate fog has been cleared away in the highlights, but the
dichromate image is still very evident as shown in the before-and
after-comparison here:

http://my.net-link.net/~jsmigiel/images/technical/gum/before_after_Cr2O7.jpg

The effect of the clearing solution is much more evident in the
before-and-after scans of the bone black pigment test:

http://my.net-link.net/~jsmigiel/images/technical/gum/before_after_BB.jpg

and the cobalt violet before-and-after test:

http://my.net-link.net/~jsmigiel/images/technical/gum/before_after_CV.jpg

In the latter two examples, the chromium image has been reduced
considerably (if not entirely as far as I can tell). The dichromate fog
is gone, the paper white shows through clearly, contrast is improved,
and the color appears more saturated. These color and contrast effects
are exaggerated in the scans, but are evident in the actual test prints.

BTW, these four prints were all cleared for 5 minutes and rewashed for
30 minutes together. I'm wondering now why it appears the pigmented gum
has allowed the chromium image to be cleared while the clearing solution
appears to have much less of an effect on the unpigmented gum example or
the straight chromium image. Perhaps less of a chromium image actually
formed under the pigmented gum in the first place and the clearing
solution therefore had less to work on and gave the appearence of
clearing those images more efficiently.

Joe
Received on Tue Dec 6 14:07:30 2005

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