Differentiation of pine and oil-based soots in East Asian inks using Raman spectroscopy

East Asian inks are a major component of calligraphy, paintings, and prints in China, Japan, and Korea and are historically made from either pine soot or oil-lamp soot mixed with a proteinaceous binder. Although the inks from the two different soot sources have different properties in East Asian works of art, no non-destructive methods to differentiate them scientifically currently exist. Raman spectroscopy (RS) of carbonaceous materials is commonly used to extract information about their properties and has been applied here to East Asian inks. Soots used in making modern inks were collected from 10 sources in China and Japan and analyzed using RS. RS using 405-, 633-, and 785-nm excitation has been able to differentiate pine soot from oil-lamp soot, also called lampblack. In addition, principal component analysis (PCA) of only 785-nm Raman spectra has been able to discriminate between two different soots used in a 19th-century Japanese woodblock printing of Kaishien Gaden. In addition to allowing discrimination between inks on East Asian works of art, these results may be of use to other fields using carbonaceous materials.