Conservation Science Now

Gettens’s further work on corrosion mechanisms and his recognition of the link between the chemistry and topography of the corroded surface helped lead to the recognition that an object’s “original surface” might still be preserved within the crust of a heavily corroded object. This discovery contributed to a gradual rethinking, since the 1960s, of the aims of cleaning: rather than attempting to restore an object to a semblance of its original form, most modern archaeological conservation tends to preserve it with its corrosion products and burial accretions, for research and study, and modifies an object as little as possible.1

Recent metallurgical studies of several Nuzi objects by scientists and students at the Massachusetts Institute of Technology have offered new insights into the metalworking technology of the period.2 The objects—arrowheads and rings—were formed by hammering and annealing precast blanks or rods. The midrib in some of the arrowheads was created by folding a flat rectangular blank, then hammering and annealing the piece to achieve the desired shape. Analysis revealed that a range of copper alloys was used at the time. Two stick pins and arrowheads were made of copper containing small amounts of tin or arsenic, which suggests that the metalsmiths either used recycled scrap metal or copper ores containing several metals. Most surprising was the discovery of some of the earliest known objects made of brass (copper-zinc alloys) with secure archaeological context from the ancient Near East. The quantity of zinc present in these objects suggests that zinc was added intentionally to produce a golden color, as distinct from the more commonly used reddish to silvery colored copper and copper-tin alloys. Both the extraction processes and the methods by which zinc is absorbed into the copper require sophistication; these objects are evidence that metallurgical know-how was well advanced some one and one-half millennia before the previously accepted date for the process used to combine copper and zinc.3

Scientists from the Art Museum are currently undertaking an analytical survey of the metal artifacts from Nuzi to determine the proportion of different alloys in each. A previous study4 of a small number of objects suggested the deliberate selection of specific alloys for different object types. Analysis of a larger corpus of artifacts is required to confirm this theory and to determine the importance of zinc-containing alloys in the overall Nuzi assemblage.

1. Bertholon 2001, 8–10.

2. Bedore Ehlers and Dixon 1998.

3. Thornton and Ehlers 2003.

4. Bedore Ehlers and Dixon 1998.