PHYSICAL AND MECHANICAL PROPERTIES OF ALBUMEN PHOTOGRAPHS
TIMOTHY VITALE, & PAUL MESSIER
5 SUMMARY OF MECHANICAL AND PHYSICAL RESULTS
The mechanical and physical evaluations of albumen prints and albumen print components reveal the following:
- Albumen (unsupported) is very weak.
- Unsupported albumen with pre-existing cracks will not exceed 1.5% stretch before failure occurs.
- Unsupported, sensitized albumen swells and shrinks 14% when taken from 14% RH to 85% RH and back to 14%RH.
- Unsupported, sensitized albumen swells and shrinks 17%+ when immersed.
- Sensitized albumen on unsized cotton paper swells 4% (CD) when immersed.
- Excessive swelling, the inability of the albumen to stretch the same degree upon drying without failure, combined with very low tensile strength of the albumen are the source of albumen cracking in albumen prints.
- Unsupported albumen has significant rate-of-strain–dependent mechanical properties.
- Albumen prints exhibit a layered structure; the layers have different mechanical behavior and dimensional response to water and water vapor.
- The mechanical properties of the albumen/ paper composite are greater than the mechanical properties of its individual components—the paper base and the albumen layer.
- Unsupported albumen shrinks 1.25% after exposure to 85% RH, but does not shrink again upon a second and third exposure to 85% RH.
- The shrinkage of albumen causes albumen prints to shrink after exposure to water.
- Albumen/paper composite shrinks 0.1–0.3% MD and 0.3–0.5% CD when rewet and dried.
- The complete shrinkage of swollen albumen appears to be inhibited by the paper base.
- Mismatch in properties of layers within an albumen print results in curl and other planar distortions.