Rehydroxylation [RHX]: Towards a universal method for pottery dating

来自UOM和UOE的一项研究最近提出了一种基于再羟化动力学的全新的考古陶瓷测年方法。这种再羟化反应是众所周知的砖石和瓷砖结构的水分膨胀和釉面陶瓷中常见的龟裂的基础(并导致)。在皇家学会发表的一篇论文中，我们提出了这种新方法的概念证明，并提供了令人信服的证据，证明通过测量水与烧成的粘土材料的化学复合所产生的缓慢渐进质量增长，可以准确地估计出2000年前的陶瓷样品的年龄。我们称这种方法为重新羟化[RHX]测年。陶器是考古遗址上越来越常见的发现，从过去的1万年开始，许多遗址的年代学都依赖于它们。然而，他们的约会在很大程度上仍然依赖于分析风格的变化。除非含有碳的包裹体或残留物存在，而且热释光可能非常复杂，否则不能应用放射性碳测年。因此，一种测定这种物质年代的新方法具有极其重要的意义。RHX的基础是所有烧成的粘土陶瓷一旦从窑中移出，就会开始增加(并膨胀)重量。重量增加是由大气湿度与陶瓷的化学结合(重新羟化)引起的，并在陶瓷的整个生命周期中持续。RHX的核心是申请者发现的一条新的时间1/4定律，它准确地定义了烧成的粘土陶瓷随着时间的推移增加重量的速度。这有效地为材料提供了一个“内部时钟”。通过重新加热以去除化学结合的水，陶瓷可以恢复到其烧成时的状态。材料越陈旧，重新加热所除去的水质量就越大。重新加热后，陶瓷与大气湿度之间的化学反应再次开始。通过监测几天内的质量增长，我们可以确定该特定材料获得质量的速度，并由此计算出通过重新加热来取代水所需的时间。这就给出了样本的年龄。到项目结束时，我们的目标是证明RHX是一种有充分依据的考古测年方法，适合常规使用。它对不同的考古场景的适用性将被确立。这项工作的总体目标是验证RHX，量化误差和不确定性，建立最终用户信心，并优化方法，以增加样品吞吐量，从而降低每个样品的成本。国际考古界的压倒性反应强烈表明，RHX可能会带来巨大的好处。这种方法被描述为“对考古学具有深远的重要性”，并“具有给考古学测年领域带来革命性变化的巨大潜力”。因此，我们的方法有可能成为对陶瓷测年的重要，就像放射性碳测年对有机材料一样重要。重新羟化过程是一个长期的幂定律动力学过程的显着例子，该过程显然跨越千年的时间尺度。这似乎是烧制粘土陶瓷中的一个普遍过程。更好地理解这一点将为超慢固相反应和传输过程领域贡献新的知识。在岩石风化和地貌学的背景下，这项工作在地球科学中有更广泛的应用。有一些非常稀少的证据表明，土壤风化反应遵循我们用于测年的相同的速率规律。认识到这些过程有一个一般的动力学框架，可能会产生强大的普遍影响。这项工作的广泛应用潜力得到了这篇论文的支持，在这篇论文中，我们发表了最初的测年结果，并在一篇关于无序高温超导体渗流理论的论文中引用了这些结果。

A research ream from the UoM and UoE has recently proposed a radically new method of dating archaeological ceramics based on rehydroxylation kinetics. This rehydroxylation reaction underlies (and causes) the well known moisture expansion of brick masonry and tile structures and the commonly observed crazing in glazed ceramics. In a paper published by the Royal Society we presented proof of concept of this new method and compelling evidence that the age of ceramic samples up to 2000 y old can be estimated accurately from measurements of the slow progressive mass gain associated with the chemical recombination of water with the fired clay material. We call this method rehydroxylation [RHX] dating. Pottery is an increasingly common find on archaeological sites from the last 10 000 y onwards and many site chronologies depend upon them. However their dating still relies to a large extent on analysing stylistic changes. Radiocarbon dating cannot be applied unless carbon containing inclusions or residues are present and thermoluminescence can be prohibitively complex. Hence, a new method for dating such material is extremely significant. The basis of RHX is that all fired clay ceramics start to gain weight (and expand) as soon as they are removed from the kiln. The weight gain is caused by the chemical combination of atmospheric moisture with the ceramic (rehydroxylation) and continues over the lifetime of the ceramic. Central to RHX is a new time1/4 law, discovered by the applicants, that defines precisely the rate at which fired clay ceramics gain weight over time. This effectively provides the material with an ''internal clock''. A ceramic can be returned to its 'as fired' state by reheating to remove the chemically combined water. The older the material, the greater the mass of water removed by reheating. Following reheating the chemical reaction between ceramic and atmospheric moisture begins again. By monitoring the mass gain over several days we can determine the rate at which that particular material gains mass, and from this we calculate the time that it would take to replace the water removed by reheating. This gives the age of the sample. By the end of the project we aim to have demonstrated that RHX is a well-founded archaeological dating method, suitable for routine use. Its applicability to diverse archaeological scenarios will have been established. The overall objectives of the work are to validate RHX, to quantify the errors and uncertainties, to build end-user confidence and to optimise the methodology to increase sample throughput and hence reduce the cost per sample. The overwhelming response from the international archaeological community strongly indicates that RHX could be of enormous benefit. The method has been described as being 'of profound importance to archaeology' and as having 'the enormous potential to revolutionise the field of dating in archaeology.' Our method therefore has the potential to become as important for dating ceramics as radiocarbon dating is for organic materials. The rehydroxylation process is a remarkable example of a long-term power law kinetic process which apparently extends over millennial timescales. It appears to be a general process in fired- clay ceramics. Better understanding of this will contribute new knowledge to the field of super-slow solid-state reactions and transport processes. The work has wider application to earth sciences in the context of rock weathering and geomorphology. There is some very sparse evidence that soil weathering reactions follow the same rate law that we exploit for dating. The realisation that these processes have a general kinetic framework may have powerful general implications. The potential for the wider application of the work is supported by the paper in which we published our initial dating results being cited in a paper on percolative theories in disordered high temperature superconductors.