Скачать или смотреть KNO2 – the chemical used in Violin-making, Adam Łapiński, March 7, 2025

Modern luthiers commonly use KNO2 to dye violin wood before varnishing. This presentation will review a study on the morphological and spectroscopic properties of spruce and maple exposed to UV light and potassium nitrite.

Chemical changes occurring after the application of this substance were monitored using vibrational spectroscopy. Moreover, the color change was studied utilizing electronic spectroscopy. The morphology of the wood surface was investigated with a scanning electron microscope (SEM). At 5000 magnification, crystalline KNO2 nodules covering the material's fibers were detected on the wood surface.

The infrared spectra were investigated thoroughly, and the origin and nature of the detected bands were identified. Changes in the intensity of the absorption bands in the spectral range of 1500–1750 cm-1 were observed. The band at 1734 cm-1, which is associated with C=O stretching in non-conjugated ketones, carbonyls, and ester groups in hollocellulose, increases in intensity during UV irradiation as a result of the degradation of lignin and the formation of chromophore compounds with carbonyl groups. However, the band's intensity did not change when nitrite was applied. The band at 1592 cm-1, associated with aromatic skeletal vibrations in lignin, intensified after applying the KNO2. A major increase in intensity was also observed in the range of 1190 – 1240 cm-1, which, in the author's opinion, can be associated with symmetric and asymmetric stretching vibrations of NO2. The author syggests that the application of KNO2 is followed by rapid surface nitration of cellulose, which through UV degradation releases volatile nitrogen oxides, trapped by guaiacol (2-Methoxyphenol) parts of coniferyl alcohol, which is one of the elements of which lignin is composed.