From Koto age to modern times: Quantitative characterization of Japanese swords with Time of Flight Neutron Diffraction† F. Grazzi, a L. Bartoli, b F. Civita, c R. Franci, c A. Paradowska, d A. Scherillo ad and M. Zoppi a Received 13th December 2010, Accepted 14th March 2011 DOI: 10.1039/c0ja00238k Japanese blades have always been considered very interesting objects, both from the stylistic point of view and their peculiar performances. It is amazing how the test and try process with a semi-empirical approach which lead to the optimization of Japanese blades, an almost ideal tool, is yet to be fully understood. In this work, we present results from a new non invasive approach to the study of these peculiar artefacts. Time of Flight Thermal Neutron Diffraction (TOF-ND) measurements were taken on two instrument INES and ENGIN-X, at the ISIS facility, RAL, UK. Two Japanese blades and eight blade fragments have been successfully characterized in terms of composition of the steel, smelting and smithing processes, and forging techniques. The differences among the production periods and forging traditions have been clearly determined. Further work is needed on standards to fully understand the production technique of a sample by comparison of the object under study with objects of known production methods. Introduction Japanese blades have been always considered very interesting objects, both from the stylistic point of view and their peculiar performances. The investigation about their shape-evolution and the manufacturing techniques is a well-established research activity. In this context, also the study of sword-forging tech- niques, and their time-evolution, represents one of the most interesting topics in this field. So far, this research activity was based mainly on standard punctual analytical techniques, like metallography. 1–3 However, this field is still lacking a well recognized experimental technique allowing a quantitative characterization of the crystal phases present in the artifact in a non invasive way, and to help to determine their role with respect to the overall features of this peculiar class of objects. Thermal neutrons, thanks to their high penetration power, 4,5 can help in solving this problem through neutron diffraction, the perfect counterpart of X-ray diffraction when the bulk micro- scopic structure of massive metal objects is to be studied. 6,7 Time of Flight Neutron Diffraction (TOF-ND) can give detailed information on several microstructural properties of the analyzed samples. In particular, for metal specimens, it can be used to quantitatively determine the relative amount of the various crystal phases composing the artifact, its conservation status, and even information on the smelting and smithing procedures, through identification of the phases related to these processes. 8 Other important pieces of information, which are available from neutron diffraction experiments, are the presence of texture, measurements of residual strains, and the determi- nation of the grain size of the phases in the sample. All these properties can be measured both as average properties (isotropic components), and as a function of a macroscopic direction (anisotropic components). 9–11 For steel samples, like the sword blades, a further important parameter accessible to neutron diffraction measurements is the carbon content of the Fe-C alloys. The different styles of Japanese sword-making are historically divided into four periods: 12,13 1) Koto (old sword): A.D. 987–1596 2) Shinto (new sword): A.D. 1596–1781 3) Shinshinto (new new sword): A.D. 1781–1876 4) Gendaito (modern era sword): A.D. 1876–present The Koto age is further split into five traditions (Gokaden). These traditions derive from the different evolutions of local replicas of Chinese double-edge blades. First, they were produced in an autochthon style and transformed in single-edge straight blades, and then they further evolved into curved single- edge blades. The five traditions were interrelated. However, the fundamental techniques, like the smelting and smithing proce- dures, the forging, and the final treatments, were different and specific. Schools of each tradition were started in a specific province and then diffused in the rest of the country. These provinces were either related to power centres: like the former a Consiglio Nazionale delle Ricerche – Istituto Sistemi Complessi, Via Madonna del Piano 10, Sesto Fiorentino (FI), Italy b Consiglio Nazionale delle Ricerche – Istituto di Fisica Applicata ‘‘N. Carrara’’, Via Madonna del Piano 10, Sesto Fiorentino (FI), Italy c Museo Stibbert, Via Stibbert 26, Firenze, Italy d Science and Technology Facility Council, ISIS Neutron Source, Didcot, OX110QX, United Kingdom † This article is part of a themed issue highlighting the latest research in the area of synchrotron radiation in art and archaeometry. 1030 | J. Anal. At. Spectrom., 2011, 26, 1030–1039 This journal is ª The Royal Society of Chemistry 2011 Dynamic Article Links C < JAAS Cite this: J. Anal. At. 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