Living organisms can induce deterioration of cultural heritage. Conservation strategies aimed at avoiding damage and aiding restoration, require a comprehensive knowledge of structure, chemical composition, and identity of microorganisms that colonize artworks. The National Theatre of Costa Rica (NTCR), a building with historic architecture, houses several oil paintings from the nineteenth century, some with visible signs of biodeterioration. One of them is a large format painting on canvas called La Danza (size 9.83 × 5.13 m) from 1896 by Italian artist Vespasiano Bignami, located on the ceiling of the theatre's foyer. In the present study, we undertook a physicochemical and microbiological study of La Danza to identify the fungal species that inhabit the artwork and are responsible for the damage observed. Scanning electron microscope (SEM) images and attenuated total reflectance - Fourier transform infrared (ATR-FTIR) spectroscopic data indicated that the canvas material is made of hemp, the binder contains linseed oil and lead white, and a material in the inner face of the canvas is mainly composed of beeswax. Fungi were isolated onto potato dextrose agar (PDA) and carboxymethyl cellulose (CMC) agar, and then identified with molecular (BTUB, nrDNA ITS, and TEF1 regions) and morphological methods. Four isolates belonging to the genera Myxospora, Pestalotiopsis, Ustilago, and aff. Penicillium, were obtained. Qualitative tests showed cellulolytic activity in all isolated specimens, confirming their possible role in biodeterioration of the canvas. Phylogenetic and morphological data revealed a new species of Myxospora we name here as Myxospora theatro sp. nov., in reference to NTCR. The findings broaden the knowledge of fungi capable of inhabiting and damaging cultural heritage. They also provide valuable information to develop strategies for conservation and restoration of oil paintings on canvas. 

Biodeterioration and cellulolytic activity by fungi isolated from a nineteenth-century painting at the National Theatre of Costa Rica

LED illumination-based multispectral imaging (LEDMSI) is a fast, convenient, and effective multispectral image acquisition technique. The square wave frequency division modulation (SFDM) and the integral sampling of the camera can build an efficient match pattern. With regards to image quality decline problems due to the ringing effect caused by the drive module while square wave high-low level conversion in the SFDM-LEDMS system. This paper proposes a multispectral image acquisition method combining Gray code and square wave frequency modulation. The micro control unit was used to generate a series of frequency division square waves in Gray code mode followed by LEDs of different wavelengths modulated by SFDM-square waves as a light source. Subsequently, the camera was used to simultaneously collect a sequence of multi-spectral images followed by single-wavelength images using differential accumulation demodulation. Finally, the no-reference image quality assessment (NR-IQA) was used to evaluate the quality of each single-wavelength image obtained by Binary code and Gray code. We deployed five wavelengths as examples to verify the effectiveness of the proposed method. The accumulated results indicated an improvement of the image quality in terms of information and gradient using Gray code. In conclusion, the present study can provide an effective image acquisition alternative for household medical equipment. 

A high-efficiency acquisition method of LED multispectral images using Gray code based square wave frequency division modulation

Over time, cultural heritage has become a key for comprehending and developing our society at an individual and group level, as it provides fundamental information about our origins, specific temporary space, materials’ availability using current technology, artist’s intention, and site weather conditions. Here, we investigated the physical characteristics of an Italian large-format artwork diptych, located on the ceiling of the National Theater of Costa Rica, to evaluate its pictorial palette as well as the tropical climatological conditions and the fungal aerial spore concentration. We characterized the role of two innovative software tools, as they have direct connection with an effective microbiological sampling and description of secrets encompassed in each pictorial layer during the process of creation and intention. We further found that eight genera of calcareous nannofossils could be associated with the optical properties of the artwork and the effects that the artist wanted to portray through his creative process.

Multidisciplinary approach to the study of artworks: environmental conditions, color palette, microbial colonization and nannofossils in Las Musas painting

This study aims to generate a multidisciplinary understanding about the complexity of the historical battle in La Trinidad de Sarapiqui de La Campana Nacional of 1856-1857, particularly in establishing a baseline diagnosis of the macrostructure, microstructure and elemental chemical analysis of a Minie bullet recovered from this historical event. We therefore carried out the first pilot study of a Minie ball recovered in 2016 in an excavation at the site of La Trinidad, in Sarapiqui, belonging to the Museo Historico Cultural Juan Santamaria. In order to obtain information on both its internal and external structure, the techniques of optical microscopy, scanning electron microscopy and elemental analysis by energy dispersive X-rays were used to determine areas of interest in the bullet and also to specify the composition of the white patina which contains primarily three types of elements: Pb, C and O. Here, we identify the possible presence of cerussite crystals in the lead carbonate surface coating in a 165-year-old Minie bullet. It should be noted that knowing the rifle of origin and its bullet is evidence of great importance to contribute to the reconstruction of the historical context in which this event took place and will therefore allow us to establish which artifacts were being used at the time, both by national and Central American adversaries.

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Estudio microestructural y elemental de una munición de la Batalla La Trinidad de Sarapiquí de 1856

Establishing affordable, efficient, accessible, innovative, and multidisciplinary methodologies to the diagnosis of the conservation state of an artwork is key to carry out appropriate strategies of conservation and consequently to the creation of modern public policies on cultural heritage. Limited access to large-format paintings is a challenge to restoration scientists seeking to obtain information quickly, in a non-destructive and non-invasive manner, and identify regions of interest. Therefore, we put forward two unique software tools based on multispectral imaging techniques, with the long-term aim to assess the artist’s intentions, creative process, and colour palette. This development paves the way for a comprehensive and multidisciplinary understanding of the mysteries encompassed in each pictorial layer, through the study of their physical and chemical characteristics. We conducted the first ever study on Musas I and Musas II, two large-format paintings by Italian artist Carlo Ferrario, located in the National Theatre of Costa Rica. In this study, we used our novel imaging techniques to choose regions of interest in order to study sample layers; while also assessing the works’ state of conservation and possible biodeterioration. We explored the applications of our two versatile software tools, RegionOfInterest and CrystalDistribution, and confirmed paint stratigraphies by means of microscopy and spectroscopy analyses (OM, SEM-EDX, Fluorescent microscopy, FTIR-ATR and micro-Raman). In a pilot study, we identified the artist’s main colour palette: zinc white, lead white, chrome yellow, lead read, viridian, along with artificial vermilion and ultramarine pigments. We were able to identify artificial vermilion and ultramarine and distinguish them from the natural pigments using CrystalDistribution to map the average size and diameter of the pigment crystals within the paint layers. This study demonstrated that software-based multidisciplinary imaging techniques are novel in establishing preventive and non-invasive methods for historical painting conservation studies, in addition, this study provides tools with great potential to be used in the future in applications such as virtual restoration.

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F. Lizano-Sánchez

Papers

Revealing time's secrets at the National Theatre of Costa Rica via innovative software for cultural heritage research.

Promotion of Remote Experimentation in Three Latin American Countries