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Principal Component Analysis of Near-Infrared Spectra of Alteration Products in Calcareous Samples

Volume 51, Number 5 (May 1997) Page 700-706

Bacci, M.; Porcinai, S.; Radicati, B.

Principal component analysis (PCA) of diffuse reflectance near-infrared (NIR) spectra has been used as a suitable methodology for discriminating areas involved in the sulfation process of calcareous stones. NIR spectra of standard mixtures containing CaSO4.2H2O, CaSO3.1/2H2O, and CaCO3 were recorded. For all data sets sub- mitted to PCA, a good discrimination between the two reaction products, i.e., CaSO3.1/2H2O and CaSO4.2H2O, in the alteration process was obtained. The actual availability of fiber-optic spectrum analyzers working in the NIR region suggests that the proposed procedure can be used as a safe and nondestructive method for monitoring alteration processes in calcareous works of art.