

Fig. 1: Martin Van Buren by Mathew Brady (NPG.76.104), half-plate daguerreotype before treatment

Mathew Brady’s c. 1856 portrait of Martin Van Buren was captured using the photographic method introduced by Jacques-Louis-Mandé Daguerre in 1839. Named for its inventor, a daguerreotype consists of a highly reflective silver-coated copper plate that has been sensitized and exposed to light. Each daguerreotype is a unique object that can appear as a negative or positive image, depending on the angle of the light.

Daguerreotype plates were typically enclosed in a package consisting of a decorative metal mat, cover glass, paper seal, and a metal foil preserver. The package was then housed in a covered wooden case. This format not only protected the plate’s fragile surface from scratches and environmental tarnishing agents but also carried on the traditional presentation of painted miniature portraits.

The components of this particular daguerreotype appear to be in stable condition, although the case hinge has started to crack. In addition, the cover glass has a grimy haze overall, which may be due to corrosion. In consultation with the curator, it was decided that the cover glass should be replaced with borosilicate glass and the daguerreotype package resealed with materials that would not attract moisture.

The object was photographed overall, and then the package was gingerly removed from the case tray. This procedure requires training and proficiency, as the object’s components and case structure are delicate. The plate was then reexamined and an inscription identifying the subject and photographer was found engraved on the plate’s verso.



Fig 2: plate during treatment



Fig. 3: Plate verso, detail, during treatment



Fig 4.Sealing the package

After the plate was rephotographed, the daguerreotype package was reassembled.



Fig 5. After treatment, before return to caset

Now the image is more legible to the viewer, and the object itself is more stable in its surrounding environment

— Christina Finlayson, Contract Photographs Conservator, National Portrait Gallery

This work has been supported by a grant from the Richard Lounsbery Foundation