Technological investigations and corrosion analysis of Archaic Greek helmets: preliminary results.
Creators: name: Manti, Panagiota
name: Watkinson, David
name: Kockelmann, Winfried
name: Pantos, E.
Publisher: name: Zenodo
Year: 2006

description: Abstract

Within the framework of an ongoing doctoral research into the technology and decoration of Greek helmets,, we present the Non-Destructive use of Synchrotron Radiation X-Ray Diffraction and Neutron Diffraction at the CCLRC Daresbury and ISIS laboratories respectively,  Two early Corinthian type helmets from the National Museum of Wales at Cardiff, whose sampling was prohibited by the fine preservation of the pieces, were analysed at ISIS-ROTAX. Neutron diffraction allowed interpretation of their manufacture method and the identification of areas that were original to one of the helmets, as compared to later additions.  In addition, corrosion and small fragments from two Illyrian type helmets from archaic period burials at Archontiko Cemetery, Greece were investigated using Synchrotron Radiation X-Ray Diffraction (SR-XRD) at station 14.1 and flat-plate geometry SR-XRD on the high resolution station 2.3 at Daresbury Laboratory. A small sample from one helmet was also analysed using Neutron diffraction at the ISIS-ROTAX station at Rutherford Appleton Laboratory. This part of analysis sought to detect Cu/Sn intermetallic compounds, whose presence cowould offer evidence for the presence of tinning.

Visual observations, metallography and SEM-EDX elemental mapping of polished samples in cross-section, indicated that the epsilon and/or eta phases of Cu/Sn intermetallic compounds may be present on Helmet 1. Compositional analysis alone is unable to discriminate between high tin surfaces formed by corrosion and Cu/Sn phases formed during tinning, as tin content of the intermetallic compounds lies within the range for tin found at tin-rich surfaces as a result of corrosion in low tin archaeological bronzes. Conventional X-Ray Diffraction (XRD) had limited success in identifying intermetallic compounds on these objects due to the small size of samples and interference from other compounds present. SR-XRD of powder micro-samples on 14.1 indicated the presence of various corrosion products (malachite, cuprite and some non-identified peaks), useful for the characterisation of the corrosion patinas on the helmets. Neutron diffraction indicated, on the basis of the counting statistics, the presence of ε-phase Cu/Sn intermetallic compound at 0.3 wt%, which is at the limit of detection. There were no indications of η- and δ-phases. The detection of some ε-phase supports the view that the microstructure observed on Helmet 1 is a remnant of tinning. More measurements of the same sample at longer counting times to increase the detection limit for the bronze phases is planned. All analyses on the second helmet indicated that tin-enrichment arose from corrosion during burial. Tinning of a helmet could be for protective (wear resistance), economical (possibly to imitate silvering) or aesthetic motives. It would however, affect the visibility of a warrior on the battlefield and mark his status or even his affiliation to a particular troop. This is a pilot study. Only by investigation of numerous helmets can the occurrence and frequency of tinned helmets be examined and placed in a historical context. 




 
description: ACKNOWLEGMENTS 








National Museum Cardiff: Ms Mary Davis for transportation of the helmets, Miss Penny Hill for access to the material and the x-radiographs, Mr Michael Lambert and Mr Tom Cotterell for support with XRD analysis, and Mr Richard Brewer for permission to study, transport and sample selected helmets. 




IZ’ Eforia of Antiquities Greece: Dr M. Akamati and Dr P. Chrisostomou, for studying permeation   




The Greek Ministry of Culture, for permitting the sampling and analysis. 




Optometry Department, Cardiff University: Prof Tim Wess and Donna Lammie for preparation of thin sections 




SRS Daresbury Laboratory: Dr Steve Buffey at station 9.6 




HISAR, Cardiff University: Dr Killian Anheuser and Mr P. Parkes for help with SEM-EDX analyses