| The astrolabe collection of the Adler Planetarium and History of Astronomy Museum, Chicago, IL, was examined using non-destructive synchrotron based high-energy X-ray techniques including diffraction, fluorescence, and radiography to determine the metallurgy, microstructure, and metal forming processes used in astrolabe construction. All high-energy X-ray measurements were performed at the Advanced Photon Source (APS) synchrotron of Argonne National Laboratory, Argonne, IL. Astrolabes from the collection were selected to represent all major astrolabe production centers possible and time periods. It was found that all European astrolabes were manufactured of traditional cementation brass by hand worked metal forming processes consistent with technology in the literature. Of the Islamic astrolabes examined, all seven from Lahore in current-day Pakistan exhibited advanced brass alloys not typical of alloys discussed in the literature. It was found that these alloys were selected for their specific hot working properties, allowing the Lahore metalworkers to more efficiently make brass sheet from which to make astrolabe components. In addition, the alloy required a fundamental change in the brass foundry process, indicating advanced Zn metal production techniques.; It was found that analysis by high energy X-rays from the APS was essential to produce data on the chemistry and microstructure from the interior of the astrolabe components in a non-destructive manner. Many astrolabe components had undergone surface dezincification due to heavy annealing during manufacturing, causing the Zn composition measured by the surface sensitive fluorescence technique to be lower than the true bulk alloy Zn composition. This would have been impossible to quantify non-destructively without the high-energy diffraction capability of the APS. The results of this study have proven the effectiveness of the synchrotron as a viable non-destructive analysis technique for examining cultural, historic, and archaeological materials. The unique characteristics of the synchrotron allow analysis techniques previously unavailable to the scientist. |
