NAST Centre, University of Rome "Tor Vergata", Via delle Ricerca Scientifica 1, 00133 Rome, Italy; Department of Chemical Science and Technologies, University of Rome "Tor Vergata", Via delle Ricerca Scientifica 1, 00133 Rome, Italy.
Department of Analytical Chemistry, University the Basque Country, (UPV/EHU), Barrio Sarriena s/n, 48940 Leioa, Spain.
Spectrochim Acta A Mol Biomol Spectrosc. 2018 Nov 5;204:55-63. doi: 10.1016/j.saa.2018.06.023. Epub 2018 Jun 7.
The study of both original and decaying compounds is relevant in understanding the chemistry behind the deterioration processes, above all in open museum contexts where environmental stressors affect the artefacts. In this sense, a combination of non-invasive spectroscopy techniques (Raman spectroscopy, μ-X-ray fluorescence and X-ray diffraction) was applied on an ancient Roman building (130 CE), the "Casa di Diana" Mithraeum at Ostia Antica archaeological site. The aim is to study the raw materials, manufacturing and decaying products of the two observed types of Roman fired bricks (red and yellow) that compose the building. The present study estimates an illite raw material of carbonate-bearing marine clay likely referring to the common deposits of central/southern Italy, which contain calcite as accessory phase and a-plastic fraction constituted by quartz, feldspar and opaques. This clay material was added with volcanic temper characterised by abundant clinopyroxene and analcime (from analcimization of leucite) that are typical of the Roman Province volcanism. The firing would be probably the result of oxidizing conditions, as proved by the hematite presence. Thanks to the existence of specific neoformed mineral phases during firing it was possible to assess different temperatures ranges. In detail, the red/orange bricks, for the existence of gehlenite (formed from calcite and its reaction with silicates), were fired at 800-900 °C range; whereas, the yellow ones are characterised by the lack of gehlenite and the disappearance of illite/muscovite, which indicates firing temperature at over 900 °C. Regarding the decaying products, the gypsum covers most of the surface of most bricks, both red and the yellow ones, but these latter are more susceptible to environmental stressors (sulphates and carbonates). Therefore, this work points out how by integrated non-invasive approaches it is possible trace back to original firing temperature, technology of manufacture, interpreting ceramic data.
对原始和降解化合物的研究对于理解劣化过程背后的化学原理是相关的，尤其是在环境胁迫因素会影响文物的开放式博物馆环境中。在这种意义下，本研究将非侵入性光谱技术（拉曼光谱、微 X 射线荧光和 X 射线衍射）应用于一个古老的罗马建筑（公元 130 年），即 Ostia Antica 考古遗址的“戴安娜之家”密特拉教庙宇。该研究的目的是研究组成建筑的两种观察到的罗马烧制砖（红色和黄色）的原材料、制造和降解产物。本研究估计了一种含有碳酸盐的海洋粘土的伊利石原材料，可能指的是意大利中部/南部的常见沉积物，其中含有方解石作为副相，以及由石英、长石和不透明物组成的 a 塑性部分。这种粘土材料中添加了以大量斜方辉石和方沸石（来自白榴石的方沸石化）为特征的火山助熔剂，这是罗马省火山活动的典型特征。助熔剂的存在证明了烧制过程中可能存在氧化条件，因为赤铁矿的存在证明了这一点。由于烧制过程中存在特定的新形成的矿物相，可以评估不同的温度范围。具体来说，红色/橙色砖块由于方解石及其与硅酸盐的反应形成钙长石的存在，其烧制温度在 800-900°C 之间；而黄色砖块的特征是缺乏钙长石和伊利石/白云母的消失，这表明烧制温度超过 900°C。关于降解产物，石膏覆盖了大多数红色和黄色砖块的大部分表面，但后者更容易受到环境胁迫因素（硫酸盐和碳酸盐）的影响。因此，这项工作表明，通过综合的非侵入性方法，可以追溯到原始烧制温度、制造技术，并解释陶瓷数据。
