Microanalytical investigation of brazilian coat of arms paintings on paper

[Display omitted] •Five Brazilian coats of arms paintings are characterized in a microanalytical approach•Artist's palette comprises traditional pigments such as ultramarine blue, indigo, Prussian blue, lead chromate and vermillion•Aluminium and brass are found in silvering and gilding instead of silver and gold, contradicting heraldic guidelines•Differences in the colorant palette and signature raise questions about the authorship of a painting•Crystalline efflorescences in one painting may indicate paint extender migration or past microbiological activity Heraldry in Latin American art of the twentieth century can be considered rare. In this context, the material composition of coat of arms paintings on paper attributed to the Brazilian painter José Wasth Rodrigues is investigated for the first time using a microanalytical approach. Microsamples from 5 municipal coats of arms dated 1932 were analysed using Raman microscopy, Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR-FTIR), and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). SEM-EDS results revealed the artist's choice of using metallic aluminium and brass in the representation of silver and gold colours, respectively. Raman microscopy analyses showed the use of traditional inorganic pigments, such as ultramarine blue, indigo, Prussian blue, yellow chromates and vermillion. In contrast, the results showed that the painting with an unusual signature attributed to the artist (W. instead of J.W.R, commonly found) contains synthetic organic dyes Orange 5, Red 53, and Yellow 1 (introduced in the 1900s). This discovery raised hypothesis of questioning authorship for this particular painting. ATR-FTIR analysis of a paint fragment from one painting confirmed the use of gum arabic as a binder. ATR-FTIR analyses of efflorescences collected from a blue paint layer of a particular coat of arms suggest protein and lipid content, raising suspicion of either the use of the tempera technique in this particular paint or remains of a past microorganism activity. Robust information was obtained on the chemical characterization of the coat of arms, enhancing comprehension of the painting techniques employed by the artist and providing insight into the production of heraldic art in Brazil at the beginning of the 20th-century.