In the newest issue of Ransom Center Magazine, photograph conservators and WUDPAC alumnae Amber Kehoe (Class of 2019) and Heather Brown (Class of 2014) talk about the care and preservation of daguerreotype collections at the University of Texas at Austin's Harry Ransom Center.
Excerpted from the June 1, 2020 article:
One of many strengths in the Ransom Center’s collections is early photography. In addition to the earliest surviving photograph produced in a camera, The Niépce Heliograph, the Center holds many beautiful examples of daguerreotypes.
The daguerreotype process was introduced in 1839 and named for Louis-Jacques-Mandé Daguerre (fig. 1). Exposed in a camera and developed using mercury vapors on a polished silver surface, a daguerreotype image is one of a kind, capturing the smallest of details with fine resolution (far better than a modern inkjet print!). Once complete, the photographer often gilded the plate to warm the tone and strengthen the silver particles, and then enclosed it in a book-like case that allowed the owner to carry and closely admire a photo of a loved one.
The experience of viewing a daguerreotype was originally very intimate and tactile. Now that daguerreotypes are primarily in museum and library collections, we generally see them several feet away, framed in an exhibition or supported on a reading room table. This is why it has been a privilege to work closely with 16 daguerreotypes undergoing documentation and rehousing in the Photograph Conservation Lab.
Conservation documentation begins with a visual examination of an object often with magnification and under various lighting conditions. Daguerreotypes are difficult to examine with the naked eye because they have a highly reflective, mirror-like surface. Therefore, photograph conservators routinely take high-quality digital images of these complex objects in order to better understand and assess them over time. Three common types of imaging used to capture daguerreotypes are normal, specular (or reflective), and ultraviolet (UV).
Normal light images capture the daguerreotype as we see it using standard lights like halogen, LED, and/or fluorescent bulbs. This type of imaging shows the daguerreotype as a positive image with the lightest areas being composed of tiny, silver-mercury-gold amalgam particles. Thin, colorful layers of metallic tarnish as well as dust, haziness, and other corrosion products on the surface of the plate can be documented using normal light imaging.
Specular light images document the daguerreotype as we see it from an angle, reflecting light off of the surface and into our eyes. Opposite of the normal light image, the specular image looks like a negative with the silver-mercury-gold particles appearing dark. The lights, camera, and daguerreotype must be carefully positioned in order to successfully capture this visual phenomenon. Specular light enhances the topography and condition issues of the daguerreotype surface. Tarnish layers, accretions, and pits that disrupt the reflection of the surface appear more visible in this light.
UV light images can reveal visibly fluorescent materials present on daguerreotypes. When certain materials are illuminated with ultraviolet light, they emit visible fluorescence due to their chemical makeup. The color of the fluorescence can sometimes be used to support the identification of materials applied to photographs such as varnishes, colorants, and adhesives. Daguerreotypes are composed of metals–copper, silver, mercury, and gold–and metals generally do not fluoresce unless they have coatings or residual signs of previous chemical treatments. The visible green fluorescence on this daguerreotype is associated with certain signs of physical and chemical deterioration: tarnish, haziness, and some deep pits that reveal the copper support. These signs may indicate that a daguerreotype has been previously treated with chemicals. In the past, removing disfiguring tarnish with chemical cleaning solutions was common practice in daguerreotype restoration.
Documenting and monitoring all visual characteristics allows us to develop guidelines for the safe handling of these sensitive objects. Careful documentation also informs appropriate treatment protocols, which always emphasize minimal intervention. Treatment typically includes removing loose surface dirt and dust with an air puffer and gently cleaning the case components where necessary.
To read the full article, visit the Ransom Center Magazine website, here.
