7.1. Case study 1

This investigation was performed by the Janet Laidla, Kadri Tinn and Ragnar Saage from the University of Tartu Museum and Institute of history and archaeology.

The purpose of this research was to try and determine the suitability of a portative X-ray fluorescence spectrometer (pXRF) for ascertaining the chemical composition of telescope mirror in a non-invasive way. The mirror probably date back to the early 19th century and was made by William Herschel and Johann Gottlieb Friedrich Schrader (although this is not 100% clear). One aim was to see whether the chemical composition of the objects was similar to what we know about the telescope mirrors of the time. 

The results of the pXRF analysis show that the chemical composition of the mirror is similar to contemporary recipes. By a recipes a mixture of copper and tin was used to make speculum metal with the addition of a variety of metals and other compounds to add strength and lustre to the telescope mirror. Analysed mirror show less copper and more tin than the recipes would allow. It cannot be conclusively determined whether this is due to the restrictions of xPRF measuring (only from the surface of the mirror) or less copper was included while making smaller mirrors in the early 19th century. [Tartu Ülikooli ajaloo küsimusi XLV (2017)]