In search of Humboldt’s colors: materials and techniques of a 17th-century lacquered gourd from Colombia

Abstract

In 2014 the Hispanic Society Museum & Library, New York, acquired a viceregal Spanish American lacquered gourd, dating to 17th-century Colombia, which was decorated using an indigenous technique known as barniz de Pasto. This technique employs local, raw materials, including natural dyes and a plant resin commonly known as mopa mopa, harvested from Elaeagia pastoensis Mora trees that grow in the Andean rainforest. An in-depth scientific study of the gourd aimed at determining its materials and manufacturing techniques, and at comparing the results with the description of local botanical species reported by Alexander von Humboldt, the German naturalist and explorer, in the account of his travels through the region in 1801. The use of several non-invasive techniques was followed by micro-sampling. Initially, X-ray fluorescence (XRF) analysis was performed to evaluate the possible presence of inorganic pigments, while fiber optics reflectance spectroscopy (FORS) and multiband imaging provided preliminary data concerning the colorants. Dyes and pigments were fully characterized using Raman spectroscopy and high-performance liquid chromatography with photodiode array detector (HPLC-PDA); a detailed description of the resin was obtained with HPLC-PDA and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS); the metallic elements and overall decoration were analyzed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS). Radiocarbon dating completed the technical information on the object. This work confirmed the identity of the resin as Elaeagia pastoensis Mora, supporting an unequivocal classification of the gourd as a barniz de Pasto object; the color palette was found to include some of the pigments listed by Humboldt, but also comprised other materials, such as calomel, a rare white pigment based on mercury(I) chloride; examination of the decoration’s intricate stratigraphy provided insight into the complexity of the barniz de Pasto technique, in which silver leaf is typically applied on top of a sheet of untinted resin and covered with a variable number of dyed resin layers; finally, a pre-1650 date was firmly established for the gourd, which is in line with stylistic observations that had tentatively placed this object in the early barniz de Pasto period. In addition to providing conservators with the proper tools to preserve similar lacquered objects, the wealth of knowledge gleaned from this study has revealed fascinating details about the technique employed, demonstrating the extraordinary skill and craftsmanship of the artisans involved in the lacquer arts.

A Recently Identified Barniz Brillante Casket at Bateman’s, the Home of Rudyard Kipling

“…White pigments on barniz de Pasto objects have historically been identified as containing lead white. Mercury white, i.e., mercury(I) chloride used as a pigment, was only recently identified [2,3,13,18,[28][29][30][31]. Only one of the two V&A objects decorated with barniz brillante featured mercury white [32], while the tray shown in Figure 6 does not contain any.…”

“…Case studies of barniz de Pasto [1] published by the V&A prompted National Trust curators to search its own collections for this material and, in 2021, the first example of barniz de Pasto was identified (NT 761758-Figure 1) at Bateman's near Burwash, Sussex. This casket is decorated with mopa mopa, a plant resin used in the manufacture of South American barniz de Pasto objects; its decoration, which includes silver leaf, is known more specifically as barniz brillante [2,3].…”

Pigments — Mercury-based red (cinnabar-vermilion) and white (calomel) and their degradation products

“…four mopa mopa objects -A 17 th century richly decorated barniz de Pasto table cabinet "probably made during the seventeenth century in the northern zone of the Vice-royalty of Peru", two barniz de Pasto gourd flasks and a barniz brilliante casket, all held by the Victoria and Albert Museum in London, UK (Burgio et al 2018;Melchar et al 2021). Please note that the authors refer to calomel as "mercury white", whenever it is clear that this material has been used intentionally as a pigment in its own right; a viceregal Spanish American barniz de Pasto gourd (mopa mopa) produced in the 17 th century (pre-1650) at Pasto in Colombia and acquired in 2014 by The Hispanic Society Museum and Library at New York in the USA (Pozzi et al 2020); -The "Fitzwilliam Missal" (MS 34), that is a 15 th century English illuminated manuscript "probably made in York around 1470 for Sir Richard Fitzwilliam and his wife, Elizabeth Clarell" and preserved in the Fitzwilliam Museum in Cambridge, UK (Crippa et al 2020); a late 16 th -century English portrait miniature "of a fashionably attired unknown lady" by Isaac Oliver's in the Fitzwilliam Museum collections (FM 3868;Crippa et al 2020).…”

The Splendour of Glitter: Silver Leaf in barniz de Pasto Objects

“…However, despite the cultural and artistic importance of these objects, few technical studies have been carried out to characterise materials [2][3][4][5] and identify their transformation over time. In particular, the lack of research with respect to the introduction and use of materials such as silver leaf and brass is evident.…”