Cacciari Ilaria, Ciofini Daniele, Baija Hubert, Siano Salvatore
Istituto di Fisica Applicata "Nello Carrara", Consiglio Nazionale delle Ricerche, v. M. del Piano 10, 50019 Sesto Fiorentino (FI), Italy.
Rijksmuseum Amsterdam, Museumstraat 1, Postbus 74888, 1070 DN Amsterdam, The Netherlands.
Materials (Basel). 2019 Nov 21;12(23):3822. doi: 10.3390/ma12233822.
Here, a systematic study in order to assess the potential of THz time domain reflectometry for measuring the thicknesses of overpaint layers applied on original gilded surfaces was carried out. The work is part of a thorough characterization campaign, which is going on at the Rijksmuseum for addressing the conservation problems of a set of 19th century gilded picture frames on which heavy coatings were applied in previous undocumented restoration interventions. To perform such non-invasive thickness measurements, an analytical protocol based on Gaussian fits of the THz pulse-echo temporal profiles was optimized through the preparation of suitable technical samples and the comparison with direct thickness measurements. Finally, the methodology was validated by characterizing the microstratigraphy of an original sculptural element from a gilded picture frame in the Rijksmuseum collection. The results achieved show the effectiveness of the present approach in revealing multi-layered dielectric microstructures with a spatial resolution of about 30 µm when using a spectral range up to 1.5 THz.
在此，开展了一项系统研究，以评估太赫兹时域反射光谱法测量涂覆在原始镀金表面的罩面层厚度的潜力。这项工作是一项全面表征活动的一部分，该活动正在荷兰国家博物馆进行，旨在解决一组19世纪镀金画框的保护问题，这些画框在之前未记录的修复干预中被涂上了厚重的涂层。为了进行这种非侵入式厚度测量，通过制备合适的技术样品并与直接厚度测量结果进行比较，优化了一种基于太赫兹脉冲回波时间剖面高斯拟合的分析方案。最后，通过对荷兰国家博物馆收藏的一个镀金画框中原始雕塑元素的微观地层进行表征，验证了该方法。所取得的结果表明，当使用高达1.5太赫兹的光谱范围时，本方法在揭示多层介电微结构方面具有有效性，空间分辨率约为30微米。
