Cultural Heritage Imaging

By Guest Blogger E. Keats Webb

I mentioned briefly last month some of the objects that we have been using Reflectance Transformation Imaging (RTI) on here at the Smithsonian’s Museum Conservation Institute (MCI).  One project involved paper “squeezes,” paper pulp molds made from the surfaces of ancient monuments at archaeological sites.

In some cases these “squeezes” are primary resources containing rare intellectual and physical information from monuments that have deteriorated or sites that no longer exist.  Unfortunately, the fragility of the paper minimizes accessibility of these objects to researchers and scholars. This makes them great candidates for non-destructive documentation of the 3-D characteristics of their surfaces with the RTI method.

Senior Conservator, Melvin Wachowiak, and I worked with the conservators from a Smithsonian museum, imaging a couple of examples of paper squeezes to see what the RTI method might contribute in terms of preservation and research.

Since the squeezes are molds taken from stone inscriptions, the writing is reversed.  After the image acquisition we “flipped” the images using imaging software, and then processed the files so that the final RTI product could be a legible rectified document for researchers to study.

We found that the RTI method increases legibility through the combination of raking light features and the specular enhancement option while also creating a surrogate that can be more extensively “handled” by researchers and scholars. (See images below.)

We continue to use RTI on a daily basis and look forward to sharing more with you about how the method is helping the scientists and conservators within MCI and the Smithsonian for the research and preservation of the collections.

Detail of Paper Squeeze with Normal Light Position

Detail of Paper Squeeze with Raking Light

Detail of Paper Squeeze with Specular Enhancement