| The analytical chemistry component of this thesis focused on instrumentation and methods to address challenges in art conservation, particularly the identification, quantitation, and reactivity of a set of representative varnishes and their degradation products. Methods for characterizing varnishes are of great interest to art conservators to restore art work more accurately. A database was created as a means to identify and quantify the composition of aged varnishes. Fourier Transform (FT)-Raman Spectroscopy was used to study common organic acids found in varnishes. The database included nine short-chain carboxylic acids, four di-carboxylic acids, and six medium-tolong- chain fatty acids. Four varnish samples (Linseed Oil, Tung Oil, Dammar, and Mastic) were studied as well. Through visual comparison and fingerprinting analysis comparison, identification of components in the Raman Spectral Database were recognized as components of the varnish samples. Singular Value Decomposition (SVD) was conducted to determine how well the database represented the unknown varnish samples. SVD was applied to the 19 standards collected in building the database. To reduce the amount of data, seven singular values were chosen. The seven singular values were then used to model several unknowns -- Linseed Oil, Tung Oil, Dammar, and Mastic. The root-mean square (RMS) error for the unknowns were 0.08, 0.13, 0.21, and 0.21 Raman Intensity units, for Linseed Oil, Tung Oil, Dammar, and Mastic, respectively. If those values are compared to the largest peak in the unknown spectra, the % relative RMS errors are 1.7%, 1.7%, 4.9%, and 6.4%, respectively.;A method based upon Gas Chromatography (GC) was developed to characterize carboxylic acids formed as a result of varnish degradation. In this method, a headspace solid-phase microextraction (SPME) approach was optimized in which a 75 im carboxen-polydimethylsiloxane (CAR/PDMS) SPME fiber was used to analyze mono carboxylic acids. For quantitative determinations, the injection port was in the splitless mode and held at 250°C for 1.0 min for the desorption of the analytes from the SPME fiber. After the initial minute, the injector was switched to a 1:100 split ratio. The temperature program consisted of the oven being initially set to a temperature of 30°C and held for 1 min, and then ramped at 25°C/min to 200°C, where the temperature was held for 1 min, thereby resulting in a total run time of 8.80 min. The PFPD was held at 200 °C for the entire run with a 0.5 ms gate delay, and the gate width was set to 20.0 ms. The mono carboxylic acids that were studied were Formic, Acetic, Propanoic, Butyric, Valeric, and Caproic Acid. A linear relationship was observed between the number of carbons in the carboxylic acid and the retention time (y = 0.75x + 1.55, R2=0.95). Quantitation of Acetic Acid was done by calibration using a first-order regression fit. The model yielded: y = 0.29x + 0.92 (R2=0.95). Using a second-order model, a better fit was found: y = 0.0025x2 - 0.0016x + 5.9 (R2=0.99).;An ageing chamber was designed, fabricated, and tested as a means for better understanding the decomposition of varnishes over time as a function of temperature, humidity, and ultraviolet light. The goal in the development of the ageing chamber was to demonstrate that it may be possible to create Standard Reference Materials (SRMs) artificially that resemble authentically aged varnishes. This is possible by the use of the ageing chamber that was built because it is directly incorporated into a GC oven where temperature, where UV radiation, humidity levels, and pollutants can be precisely controlled and carefully monitored. The GC method for carboxylic acids described above was developed to aid in the measurement of carboxylic acid fragments that could arise from the ageing process. There are promising results of the Raman Intensity increasing as the sample aged. |
