Introduction

Metallography in its broadest definition encompasses all aspects of the characterization of the structure of metals and alloys, and the objects made from them, in relation to their composition and properties. In an archaeological context a very wide range of metallo-graphic techniques can be used to write and collate the biographies of metal artifacts based on the premise that every process or event in the life of an artifact from manufacture to conservation leaves a trace that potentially can be read. In doing this methods will be used that are described in other sections of this work besides the variety of microscopic methods which form the core of this article. A further general point relates to resolution: at all levels of resolution from the macro - to the nano - there is information of relevance, indeed of importance, to archaeology. As an example, what was possibly the first application of high-resolution electron microscopy (HREM) to archaeology was in elucidating the structure of the glossy black surface of Chinese mirrors from the Han Dynasty. This is an important issue because archaeology has tended to be content with examining metal with a restricted resolution, rarely exceeding the power of the optical microscope and the wavelength limit of light. Going beyond this with any appropriate technique can open up completely new avenues of research. A case in point is the characterization of intergranular corrosion using high-resolution scanning Auger microscopy. This showed that between the majority cuprite corrosion product and the bronze grains was a layer of cassiterite (tin dioxide) only 70 nm thick: this had not previously been suspected because the question had never been examined at that resolution, while its identification can open the way to an improved understanding of internal corrosion in copper alloys.