U of S | Mailing List Archive | alt-photo-process-l | Re: Printing gum with little pigment

Re: Printing gum with little pigment

On Fri, 16 Jan 2009, Marek Matusz wrote:
Two sets of tests are done with same water/gum/dichromate but different pigment concentrations. I have made different exposures and tested two development times. I used indantrone blue which is a wonderful dark blue and non-staining. I can not see that low pigment concentration extends the rane of gum print, to the contrary it allows less steps to be separated on a standard step tablet. One of the tests is also a good illustration of how delicate highlights with dark shadows can be printed with the same negative with the postflash. Anybody else want to chime in. It would be great to see some illustrations. A picture is worth a thousand words. This contrast vs. pigment issue has been on my mind for a while. Marek
For several thousand dollars or a gun at my head (or both!) I could locate the test strip(s) I did with the very low and no pigment variations, long years ago.

Barring the threat or offer, I note, on my scout's honor, I did them and they reside in a folder in a milk crate full of folders of test strips in the studio.

I doubt I showed them in P-F, as it was more a whim of personal curiosity than to make a particular point or a propos of anything in P-F at the time. However, let me clarify (tho I think Chris or/and Katharine made these point(s) on the list yesterday or today):

Exposure was NOT the same, as that was not the point of the exercise, which was to see how long a scale was possible with "gum" by whatever means. With less (or no) pigment blocking light, even the same time would "expose" more. Nor do I remember whether or not development was the same -- maybe, maybe not. But, again, that wasn't the point of the exercise, which was to find the possible range of the materials, by whatever means.

However, there is an early variant/hint in P-F #2, page 46, "One Little Test." This was done to debunk Anderson's (that's Paul's, not Chris's) inane "Gum/pigment ratio" test:

I showed two test strips, one with twice the pigment of the other, both otherwise treated the same. The one with double pigment had a shorter scale and less "stain" than the other. (Tho stain didn't show clearly in repro, but the scale did).

Obviously, longer development could open the blocked-up dark steps of the strip with the double pigment, thus extending the scale, tho top steps might be washed off at the same time. Whether the same number get washed off as get added depends on variables of ingredients, agitation, etc. (in my experience, and in tests I made students do, they were rarely the same, tho theoretically I suppose they could be). BUT, if all other variables are the same, the one with less pigment should show a longer scale.

And it did.