Defense: Heidi Kastenholz - "Applications of Nonlinear, Femtosecond Laser Systems for Understanding Artists’ Historical Pigments"

Title: Applications of Nonlinear, Femtosecond Laser Systems for Understanding Artists' Historical Pigments

Abstract: The field of technical art history brings together scientists, conservators, and curators to better our understanding of artists' materials and their works. The technical toolbox for analysis includes techniques that observe how light interacts with a sample, such as reflectance spectroscopy, Raman spectroscopy, or x-radiography. While these techniques have their strengths, there are still some materials that prove difficult. Here, I discuss the use of nonlinear optical techniques, such as pump-probe microscopy, to expand the toolbox to address materials that are otherwise challenging with conventional techniques.

In chapter 4, I will focus on the study of four of the most commonly used carbon-based black pigments. These pigments are often difficult to study with noninvasive methods as they are primarily carbon-based and black in color, meaning there is little differentiation that can be done elementally or spectrally. I demonstrate the ability of pump-probe microscopy, coupled with a simple machine learning algorithm, to differentiate the four carbon-based black pigments focused on not only in individual paint-outs, but also in two-black pigment mixtures and when each black pigment is mixed with a historically relevant colorful pigment.

Chapter 5 shifts to my work constructing a system that combines pump-probe microscopy with stimulated Raman scattering. Raman spectroscopy is a powerful tool for identifying pigments due to its molecular specificity. By coupling the nonlinear version, stimulated Raman scattering, with pump-probe microscopy, my goal is to achieve co-registered data for samples where Raman data and pump-probe date could provide complementary information.

Technical art history comes back to be the main focus in chapter 6 as I discuss my collaboration with the Nasher Museum of Art over the course of the past year. This work stems from both pedagogical and technical efforts to support an art history course, Curatorial Practicum, and the resulting gallery exhibition, On the Same Wavelength: Art, Science and Conservation, that was at the Nasher Museum of Art. I will share insights gathered from the technical analysis on the museum objects performed by myself and collaborators.