The influence of different tempers on the composition of pottery
The modification of the raw clay by the potter to produce a paste suitable for the intended purposes adds a layer of obfuscation to the problem of provenancing the original clay source by chemical fingerprinting. By preparing different pastes from the same commercially available raw clay and their chemical analysis by Instrumental Neutron Activation Analysis, an experiment under controlled conditions (tempers, mixing ratios, firing temperatures and sampling methods) sheds light on the influence of different tempers. The results show that two different sampling procedures (drilling and grinding) have almost no influence on the chemical fingerprint with the exception of the elemental concentrations of As, Zr, and Hf. This may be due to the volatility of the compounds (As) or the presence of zircon crystals (containing Zr and Hf) which are partly lost during drilling. Three different firing temperatures show no significant influence as well. The application of the modified Mahalanobis distance introduced by Beier and Mommsen in 1995 as a statistical filter and the introduction of a ‘dilution factor’ to the raw data show that the influence of quartz-dominated tempers can be filtered out of the data, resolving the underlying chemical fingerprint of the original clay source. At the same time, by mathematically removing the additional spread introduced by dilution, even subtle differences between similar pastes can be resolved by standard multivariate statistical means.
Pottery production on Rishiri Island, Japan: perspectives from X‐ray fluorescence studies
Energy-dispersive X-ray fluorescence (EDXRF) was used to determine the minor and trace element composition of 54 sherds of pottery dating from the Final Jomon to Okhotsk periods. The majority of the sherds came from Rishiri Island, Japan. Principal component (PC) scores were calculated using the log transformed concentration values, and groups were sought in the PC scores using kernel density estimates (KDEs). Two main groups were found in the data; linear and quadratic discriminant analysis classified both groups successfully. Significant differences in the concentrations of Cu, Fe, K, Nb, Pb, Rb, Th and Zr were found to exist between the two groups. The lack of correspondence between chronological ware types and geochemical groups implies that the same raw materials and paste recipes were in use during the Epi-Jomon and Okhotsk eras on Rishiri Island. One possiblity is that the Epi-Jomon and Okhotsk potters used the same clays and tempers, since no other alternatives were available. Alternatively, the Okhotsk potters could have adopted the same paste recipes as the Epi-Jomon potters, or the Okhotsk pottery tradition could be descended from the Epi-Jomon pottery tradition.
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.