39th Annual Meeting, ASG Morning Session, June 2nd, Student Papers, “Non-Destructive Investigation of Concealed Gilding in Architecture” by Angela Curmi, Columbia University

As an objects conservator, I tend to overlook the decorative walls of a historic house, focusing instead on the surrounding 3D aspects.  Angela’s talk really made me stop and think about the walls, as not only a significant work in themselves, but also as a record for changes in style and taste.  However the problem becomes, how do you look at certain aspects of previous wall decoration without removing the layers of historic paint?  Furthermore, how do you look at the overall motif of an entire room, without removing paint from the entire room?  Angela’s thesis from her studies at Columbia University focused on non-destructive methods of detecting gilding under layers of paint.


For her research, Angela created mock-ups of gilding motifs using gold, silver, and aluminum leaf under 3-5 layers of various paints (enough to provide visual coverage) and relied on infrared reflectography, infrared thermography, and eddy currents to see if gilding could be detected non-destructively.  The pigments of the paints can interfere with the ability to image so Angela chose historic lead white paint,  calcimite paint, and modern ‘Latex Paint’ along with burnt sienna, chromium oxide, yellow ochre, and Prussian blue [PHOTO ] on prepared wood panels [PHOTO].  For equipment Angela used a modified Kinamax nightvision webcam, modified Nikon Coolpix IR Camera, and Indigo Systems INGaAs NIR camera to test the Infrared Reflectography, as well asFLIR ThermaCAM P640 and FLIR Inframetrics InfraCAM to test the Infrared Themography [PHOTO].


Several years ago I had to attend a conference on IR imaging in an attempt to find the most practical model for my lab, so I empathized with the literature and technical data that Angela must have had to sieve through in order to find an appropriate model for her imaging.  Her results were much like I experienced, there is no ‘best’ suited for a conservator’s needs.  As Angela stated there were drawbacks to all systems, either in their range of wavelengths, ease of software use, or the quality of the image produced.   She did not find success with Thermography, mostly because of the inefficiency of heating a large space evenly to get the image.  Reflectography was more promising with the best results achieved with the Indigo INGaAs NIR camera, though its use is not necessarily practical based on cost.  The most practical model appeared to be the Kinamax model, an affordable, easily used modified web camera, the result of collaborative research from Elizabeth Nunan and Greg Smith at Buffalo State College.  For more information and purchasing of your own model go to Elizabeth’s website:  http://www.aandnartconservation.com/infraredsensitivewebcam.html