Merging of imaging techniques based on reflectance hyperspectral and neutron tomography for characterization of a modern replica of a 13th century knife from Croatia

Abstract

A large amount of iron and steel artifacts produced in the central European area between 2nd and 14th Centuries is constituted by pattern welded iron-phosphoric iron and steel components. Phosphoric iron is a substitutional alloy, which is obtained by using iron ore from swamps in which decomposition of dead organisms enriches the iron rich soil with phosphorous. The identification of phosphoric iron alloy in ancient artifacts is important for determining their place of origin, production procedure and technological characteristics. A well-established technique for investigating the bulk structure of ancient metallographic artifacts is neutron tomography, using cold neutrons. It provides image-data capable of enhancing differences between phosphorous rich iron and the standard iron areas. However, neutron imaging is costly and complex to implement. Therefore, the exploration of new techniques capable of providing additional data on the nature of alloys would be highly needed. A pilot study addressed to test the applicability of reflectance hyperspectral imaging to the investigation of ancient metallographic artifacts is presented here. So far this technique has been used for diagnostics of polychrome surfaces, but it has never been applied to investigation of metallic surfaces. Hyperspectral imaging in the VIS-NIR range (400-1700 nm) was applied on replicas of a historical object from the archaeological site of Kobilic (Croatia). The same replicas were analyzed also using neutron tomography. Hyperspectral data were elaborated to map the distribution of the different phases on the surface. The comparison of the hyperspectral data with the neutron tomography data-images provided prominent similarities. These preliminary results encourage further investigations on merging these two imaging techniques for novel applications on archeo-metallurgy.