Characterization of 17th-19th century metal threads from the colonial Andes

In a detailed study of South American metal threads, samples of metal embroidery and decorative metal leaves found on colonial Andean ecclesiastic objects have been investigated in order to characterize their composition, manufacture, and deterioration. The samples were examined with a range of methods, including optical microscopy, x-ray fluorescence spectroscopy, x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectroscopy, and Fourier transform infrared spectroscopy. The results show that the studied metal threads are made from gilt silver, or brass- or silver-coated copper, with elemental compositions and manufacturing techniques similar to metal threads found in Europe and Asia. Since all metal threads so far encountered in South America date to after the arrival of Europeans, it has been suggested that they were first introduced to the continent by the Spaniards. Although it cannot be determined whether the analyzed metal threads were imported or locally manufactured, the similarity to European metal threads suggests that the examined samples were produced according to the European tradition, without any local Andean modifications to the design patterns or manufacture processes. This strengthens the hypothesis that no tradition of metal-thread-making existed in South America in precolonial times.