The Light Farm

12. Silver Gelatin P.O.P. — A Few Observations on Recipe #1 vs. Recipe #2

November 17, 2020. I think color is what generally first come to mind with P.O.P. Except for the simplicity of the process there's really no other reason to make gelatin P.O.P. By most criteria, developing-out paper is superior. However, P.O.P. does have color!

Color is a consequence of both the basic recipe ingredients and toning. The effects can be subtle or not-so.

Left: Baker KCl/citric acid emulsion (Recipe #1). The lefthand print is developed in straight hypo. The righthand print is developed first in hypo and then in hypo & gold toner.

As I understand the history of P.O.P., prints were usually printed without a border, the image right to the edge of the paper. There were two reasons for this. First, many of the negatives were glass plates. A glass plate becomes the glass in a contact printing frame. Except for a bit of rebate around the window, a print is necessarily the same size as the negative.

Another reason, even when printing with film negatives (not so fussy about printing frame size) — toning baths were usually reused until the gold was exhausted. The more silver the gold has to replace, the faster a bath has to be replaced. A non-image border was often considered a luxury that just used up expensive gold chloride.

However...(and isn't there always an however), there is a certain amount of color shift around the edges of print. This is more pronounced in Recipe #1, Baker KCl/citric acid, which is unhardened. I usually print a bit of solid border. If a color shift is visible, it can be trimmed off.

I haven't looked carefully at Recipe #2 yet, which is hardened with chrome alum. It is a very different recipe.

Far left: An enlarged crop from the lower right-hand corner of the left-hand print above.
Near left: A color shift is particularly noticeable in highlight areas on the edge of a print, usually sky.

Color Differences Between Emulsions

Above left: Recipe #1 (Baker KCl/citric acid), plain hypo developer, untoned
Above right: Recipe #2 (Ammonium chloride/sodium potassium tartrate/citric acid), plain hypo developer, untoned

The above two prints were exposed under UV light (Edwards Engineered Products, UV light box; The exposure was only 7 minutes. A non-UV light panel is about an hour. Note the density in the highlight areas. This doesn't show up in the non-UV light prints. I think different negatives may be required for the different light sources, but I haven't chased that down yet.

For the print on the right, note the variation in density around the border. I failed to center the printing frame in UV box. oops. Whether or not maximum density is achieved in the border is a matter of personal taste. However, if the border had been uniformly pale, that would have meant that maximum density had not been achieved in the shadows of the print. Dmax in shadows isn't required with all prints (think high key), but hitting the full contrast range potential of a printing process is usually the goal.

One last word here about color. Toning.

The print on the left is Recipe #1, untoned (printed with non-UV light).

The print on the right is the test print for the full print from Recipe #2 (on the left in the set above this one), re-wet and toned with an ammonium thiocyanate/gold toner. The toner was from Clerc and I'll post the recipe again on page 13. If you prefer making and coating Recipe #2, but aren't crazy about the orange color, then toning may be the ticket.

Toning was not actually the last last word. Color can always be applied. There are oils, dyes, and colored pencils. Don't forget encaustic (high on my wanna-try list). This print is Baker KCl/citric acid, toned in hypo & gold, selectively colored with Marshalls Photo Retouch dyes. The negative was a digital negative made from a scanned handmade emulsion paper negative.

Note the subtle blue tint that the gold introduces. (In my opinion) that doesn't work for all subjects, but for some it's perfect.

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