Semiautomatic Toolmark Classification in Chased Metals Using Surface Microtopography

Abstract

Chasing is one of the main decorative techniques found in metal work. The imprints left by different chasing tools are unique not only to the tool, but also to the chaser. The analysis and characterisation of toolmarks provide vast information that is valuable for the understanding of an object. Microtopography is a non-contact imaging technique that allows a metrical analysis of a surface on a microscopic scale. In this paper, metal mock-ups made using different chasing tools were scanned using microtopography, and their morphological features were used to classify the tools used for their fabrication. The mock-ups were artificially aged to replicate conditions of real archaeological metal objects. The overall classification accuracy obtained for the non-aged mock-ups was 91% for brass and 84% for copper mock-ups. After ageing, the classification accuracy was 65% for brass and 68% for copper. The change in classification accuracy before and after ageing was caused by the corrosion on the aged mock-ups. These results show that this is a promising methodology that could be applied on real chased metal objects.

Keywords

• chasing
• toolmarks
• microtopography
• artificial ageing
• metal
• micromorphology