Exposing the sub-surface of historical daguerreotypes and the effects of sulfur-induced corrosion

• Ungilded and gilded daguerreotypes were prepared in the laboratory.
• Processing conditions were correlated to microstructures and behavior to S exposure.
• The observations revealed key structural consequences of the gilding process.
• Corrosion of the Ag layer was confirmed on a 19th century gilded daguerreotype.
• Cu and Ag sulfide particles accumulated on the plate surfaces during corrosion.

Preventing the loss of image detail and resolution in historical photographs is a crucial topic, yet the properties of the image particles and mechanisms of deterioration are not fully understood. Through detailed surface and cross sectional analyzes, ungilded and gilded daguerreotypes prepared in the laboratory were analyzed before and after exposure to high sulfur-concentration environments revealing important structural consequences of the gilding process. Comparisons with the surface and sub-surface structures found on a 19th century gilded daguerreotype confirmed the slow corrosion of the underlying Ag and the accumulation of Cu and Ag sulfide particles on the surfaces of the plates.

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