Characterization of corrosion products on old protective glass, especially daguerreotype cover glasses

The daguerreotype surface as a SERS substrate: characterization of image deterioration in plates from the 19th century studio of Southworth & Hawes

“…Once the glass deterioration cycle starts, decomposition products are trapped and contaminate the microenvironment. 8,12,13 Barger et al categorize decomposition products found on the cover glasses as follows: amorphous gels, crystals found in these gels, products formed by the interaction of the gel with the surface or the brass mat or the underlying daguerreotype, and other products. Using primarily a combination of optical microscopy, SEM-EDS, and X-ray diffraction, sodium sulfate, barium sulfate, ammonium bromide, silver, silver chloride, silver phosphate, sodium formate, and cuprite were identified in these products.…”

“…Using primarily a combination of optical microscopy, SEM-EDS, and X-ray diffraction, sodium sulfate, barium sulfate, ammonium bromide, silver, silver chloride, silver phosphate, sodium formate, and cuprite were identified in these products. 8,12 Glass decomposition products also can transfer to the daguerreotype surface. 8,13 Copper-containing corrosion products are repeatedly encountered on daguerreotype surfaces.…”

Eyeing the past: synchrotron µ-XANES and XRF imaging of tarnish distribution on 19th century daguerreotypes

“…4, which shows the presence of C, Cu and O. The C and O are indicative of organic contamination while the Cu may be assigned to diffusion from the underlying plate through grain boundaries and/or at edges of the daguerreotype (Marquis et al, 2015), though this diffusion mechanism has been questioned (Robinson, 2017 rioration of the cover glass, which has been shown to produce Cu deposits on the surface (Barger et al, 1989).…”

“…Deterioration of the cover glass could also lead to the production of AgCl as a result of alkali ions in the cover glass matrix interacting with water vapour (Barger et al, 1989).…”

“…Excess halide is removed with a thiosulfate solution (Da Silva et al, 2010). Once completed, the image is placed in a protective case, which includes the plate, a mat (usually stamped brass) and a glass cover (Barger et al, 1989). Later improvements to Daguerre's process included the use of chlorine and bromine in the sensitizing step, thus reducing the exposure time to a few seconds, and a gilding step using a gold(III) chloride thiosulfate solution (Ravines et al, 2016b).…”