To analyze the impact of solvents on collection materials, one must consider many variables:
- What is the composition of the collection item? Different photographs have different types of layers (such as silver in gelatin on baryta on paper, or silver in albumen on paper).
- What type of solvent is used (acetone, toluene, ethanol or others), and how do different solvents effect the various layers of various photographic processes?
- How is the solvent applied (using a poultice, a suction table, a bath or some other alternative)?
- How old or deteriorated is the photograph?
These are just some of the variables that must be addressed and controlled to understand the effect of solvents on photographs.
Project Description: To address some of the variables germane to the effect of solvents on photographs, the Library of Congress has developed a feasibility study. The feasibility study is designed to evaluate one commonly used solvent (acetone) on the most common photographic process of the 20th century, silver gelatin developed out print.
Optical properties of photographic grayscale stepwedges will be characterized before and after treatment and accelerated aging by:
- Densitometry
- Reflectance/gloss
- Scanning Electron Microscopic Imaging
- Hyperspectral Imaging
- Colorimetry
- Hardness
For the purposes of the study, and for maximum effect, the first solvent application technique to be simulated will be solvent saturation. Areas to be examined include the portion of the photograph where solvent was directly applied, as well as at the interface of the solvent and the untreated areas
Acknowledgements: This project is a joint effort between the Conservation Division and the Preservation Research and Testing Division of the Preservation Directorate.
