Taking a Deeper Look: Attributing Tonal Values of Photolumens to Their Emulsions Using Scanning Electron Microscopy

Author

• Anna M. Moore, Clemson UniversityFollow

Date of Award

5-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Graphic Communications

Committee Chair/Advisor

Erica Walker, PHD

Committee Member

Carl Blue, PHD

Committee Member

Elizabeth Carraway, PHD

Committee Member

Prof. Danita Swaney

Abstract

This thesis examines whether tonal variation in photolumens made with historic silver gelatin photographic papers can be linked to differences in elemental composition. Photolumens are cameraless photographic images created by placing objects directly on light-sensitive paper and exposing them to ultraviolet light. Because expired and historic darkroom papers often produce unpredictable colors and tones, this study asks whether visually defined tonal groups also show measurable chemical differences.

Twenty historic paper samples were exposed, documented, and sorted into five tonal groups based on visible image characteristics. Each sample was then analyzed using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) to measure elemental composition by weight percent. Comparative datasets were evaluated across groups, with emphasis on silver and halide-related components because of their importance in traditional photographic emulsions. The study also tested total silver-halide-related content and the ratio of silver to total halides. Because ytterbium appeared in several samples despite being historically unlikely in these materials, a second interpretive model treated the ytterbium signal as a probable bromine peak-overlap artifact.

Results showed that many elements were widely distributed and did not independently distinguish tonal groups. No significant relationship was found between tonal group and total silver-halide-related content alone. No significant group differences appeared when the halide balance used the reported ytterbium values directly. However, when ytterbium was reassigned as part of the bromine-related signal, the silver-to-total-halides ratio differed significantly across tonal groups. These findings suggest that emulsion chemistry, especially silver-halide balance, may help explain tonal variation in photolumens, while also highlighting the interpretive limits of SEM-EDS analysis for layered historic photographic materials.

Recommended Citation

Moore, Anna M., "Taking a Deeper Look: Attributing Tonal Values of Photolumens to Their Emulsions Using Scanning Electron Microscopy" (2026). All Theses. 4734.
https://open.clemson.edu/all_theses/4734