FTIR spectroscopy of woods: A new approach to study the weathering of the carving face of a sculpture

• We are looking for a new approach to determine if a wooden sculpture is ancient.
• We have studied the water content inside wood through FTIR characteristics.
• In particular, the ratio of two signals around 3400 cm−1 and 1610 cm−1 is explored.
• The ratio of the two signals from the surface to the inner part of the wood decreases for ancient wood.
• The first data indicate that the ancient wood has a behavior in opposite with young wooden sculptures.

Fourier transform infrared spectroscopy (FTIR), a useful method to study woods, has been applied in order to measure an eventual gradient of water absorbed (more precisely, hydroxyl groups, OH) between the surface and the inner part of an ancient and a modern wooden sculptures. The methodology adopted has consisted in comparing FTIR bands within two spectral ranges, one corresponding to the OH content in the wood (around 3400 cm−1) and the other to the lignin molecules (aromatic CC, around 1610 cm−1). The ratio between the intensities of the peaks leads to a self-normalization of the measurements which avoids the effects of some experimental parameters (such as sample preparation).The results obtained show that there is a significant and progressive penetration of OH groups from the surface to the inside part of the ancient sculpture (more OH on the surface than inside the wood, due to the aging of the surface and the creation of sites which are able to fix OH groups). In contrary, for the modern one, we measure an increase of OH contents from the surface to the inner part of the sculpture.

Figure optionsDownload as PowerPoint slide