The Green Hues of an Iodide-based Gelatin Silver Print

The deep green hue of this gelatin silver print is unusual and is outside the range of what is generally possible by selection of papers and developers, so we used XRF analysis to dig a little deeper. Other than the usual gelatin silver prints suspects (silver, barium, and strontium) the only other peak is a very small peak at about 7.48KeV, just right for the K-alpha peak of Nickel. At first we thought we had discovered a new nickel-based toner, but soon realized that the nickel peak is due to internal components of the portable XRF unit, so it appears that while unusual the green is not the result of toning but rather an unusual paper. After a little research we found this article on green-hued prints: http://unblinkingeye.com/Articles/Green/green.html. It seems that silver-iodide based gelatin silver prints sometimes show this green tonality. The early 20th century subject matter fits with the iodide papers available at that time.