On the Chemical Signature and Origin of Dicoppertrihydroxyformate (Cu2(OH)3HCOO) Formed on Copper Miniatures of 17th and 18th centuries

A corrosion product rarely reported in the literature has been found on the copper support of three miniature paintings of the 17th and 18th centuries. This product, which has been identified as dicoppertrihydroxyformate (Cu2(OH)3HCOO), is an unusual basic copper formate found on copper artifacts. The identification and characterization of dicoppertrihydroxyformate was carried out directly over the corroded surface of the objects, using a nondestructive approach, which combines the integrated use of various microanalytical techniques. Using this approach, it was possible to obtain a set of new reference data about the natural form of Cu2(OH)3HCOO, that will enable its unambiguous identification in other similar objects. In this work, the probable causes that may have contributed to its formation are also discussed.

Tortoiseshell or Polymer? Spectroscopic Analysis to Redefine a Purported Tortoiseshell Box with Gold Decorations as a Plastic Box with Brass

The study and preservation of museum collections requires complete knowledge and understanding of constituent materials that can be natural, synthetic, or semi-synthetic polymers. In former times, objects were incorporated in museum collections and classified solely by their appearance. New studies, prompted by severe degradation processes or conservation-restoration actions, help shed light on the materiality of objects that can contradict the original information or assumptions. The selected case study presented here is of a box dating from the beginning of the 20th century that belongs to the Portuguese National Ancient Art Museum. Museum curators classified it as a tortoiseshell box decorated with gold applications solely on the basis of visual inspection and the information provided by the donor. This box has visible signs of degradation with white veils, initially assumed to be the result of biological degradation of a proteinaceous matrix. This paper presents the methodological rationale behind this study and proposes a totally non-invasive methodology for the identification of polymeric materials in museum artifacts. The analysis of surface leachates using 1H and 13C nuclear magnetic resonance (NMR) complemented by in situ attenuated total reflection infrared spectroscopy (ATR FT-IR) allowed for full characterization of the object s substratum. The NMR technique unequivocally identified a great number of additives and ATR FT-IR provided information about the polymer structure and while also confirming the presence of additives. The pressure applied during ATR FT-IR spectroscopy did not cause any physical change in the structure of the material at the level of the surface (e.g., color, texture, brightness, etc.). In this study, variable pressure scanning electron microscopy (VP-SEM-EDS) was also used to obtain the elemental composition of the metallic decorations. Additionally, microbiologic and enzymatic assays were performed in order to identify the possible biofilm composition and understand the role of microorganisms in the biodeterioration process. Using these methodologies, the box was correctly identified as being made of cellulose acetate plastic with brass decorations and the white film was identified as being composed mainly of polymer exudates, namely sulphonamides and triphenyl phosphate.

Simplified Chinese lacquer techniques and Nanban style decoration on Luso-Asian objects from the late sixteenth or early seventeenth centuries

The meeting of multiple cultures and their mutual influence during the Portuguese expansion in Asia led to the emergence of different types of fusion styles in objects commissioned by the settlers, merchants, and religious orders present in Portuguese India. The east-Asian lacquer coatings of modestly sized wooden objects of various types dating from the sixteenth and early seventeenth centuries have been analyzed as part of the research for a doctoral thesis that aims to establish their cultural and geographical attribution within the context of the Getty Conservation Institute’s lacquer research project. Among the objects were three seventeenthcentury lacquered trays from Portuguese museums and private collections that had previously been classified as Japanese Nanban, Chinese or Ryukyuan lacquers or even as Indo-Portuguese artifacts. The materials and techniques that were identified show close similarities with Chinese techniques mentioned in historic accounts — the only existing Ming Chinese Treatise on lacquering Xiushi lu and the eighteenth-century memoirs of the Jesuit priest d’Incarville. These nearly 400-year-old artifacts are among the first lacquered objects commissioned by Europeans and probably the first of Chinese origin. Their detailed technical study contributes to international lacquer research and complements existing knowledge and perceptions of the lacquering processes that were applied in response to an early European demand for exotic items.