Black Patinas Research Articles

Selenium-based black bronze treatment, as compared to other patination technologies of ancient and historic black bronzes

Metalworkers have used black patinas on high-status diminutive bronzes in the Mediterranean and Far East beginning in Antiquity. The textual evidence for these bronzes can be ambiguous, but their compositions have been intensively studied and characterized in recent decades. In addition to the ancient technologies, elemental and molecular analysis of black bronzes across millennia and cultures reveals the frequent presence of selenium-based patinas, which we have identified as copper selenite dihydrate. Selenium patination formulations have long been viewed as the 19th century response to the black patinated alloys (such as shakudō and shibuichi) that arrived in Europe from Japan beginning in the Meiji restoration. However, the 19th century European technological literature does not support this, and so selenium-based patination technologies have remained obscure. In this paper, we examine the proliferation of selenium-based technologies in the early 20th century, along with the merits of hypotheses for their origins in patina formulations.

Degradation Products on Byzantine Glasses from Northern Tunisia

This study deals with the identification of the degradation products present on some Byzantine glasses coming from an archaeological excavation in Northern Tunisia. The main purpose of the present investigation is the identification of the products and the characterization of surface altered points, namely iridescent and black patinas, which are present on some selected glasses. Non-destructive techniques such as XPS (X-ray Photoelectron Spectroscopy), SEM-EDS (Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy), ATR-FTIR (Attenuated Total Reflection-Fourier Infrared Spectroscopy) and LA-ICP-MS (Laser-Ablation Inductively Coupled Plasma-Mass Spectrometry) are here exploited. SEM-EDS was employed to ascertain the morphological structure and the chemical composition of various points, apparently different, on the glass surfaces. Small area XPS was performed for identifying the elements present on the sample surface, for determining their chemical state and for establishing the atomic composition of the morphologically different regions. LA-ICP-MS was exploited to determine the chemical composition as far as the trace elements are concerned. The presence of iridescent patinas and of encrustations has been highlighted on the glass surfaces in correspondence to the altered areas: iridescent patinas are due to the fact that the glasses are depleted in alkali and alkaline earths. The incrustations resulted due to the presence of calcium carbonates, and/or oxyhydroxides. In one case sulfides were also detected by SEM.

Characterization of black patina from the Tiber River embankments using Next-Generation Sequencing.

Black patinas are very common biological deterioration phenomena on lapideous artworks in outdoor environments. These substrates, exposed to sunlight, and atmospheric and environmental agents (i.e. wind and temperature changes), represent extreme environments that can only be colonized by highly versatile and adaptable microorganisms. Black patinas comprise a wide variety of microorganisms, but the morphological plasticity of most of these microorganisms hinders their identification by optical microscopy. This study used Next-Generation Sequencing (NGS) (including shotgun and amplicon sequencing) to characterize the black patina of the travertine embankments (muraglioni) of the Tiber River in Rome (Italy). Overall, the sequencing highlighted the rich diversity of bacterial and fungal communities and allowed the identification of more than one hundred taxa. NGS confirmed the relevance of coccoid and filamentous cyanobacteria observed by optical microscopy and revealed an informative landscape of the fungal community underlining the presence of microcolonial fungi and phylloplane yeasts. For the first time high-throughput sequencing allowed the exploration of the expansive diversity of bacteria in black patina, which has so far been overlooked in routine analyses. Furthermore, the identification of euendolithic microorganisms and weathering agents underlines the biodegradative role of black patina, which has often been underestimated. Therefore, the use of NGS to characterize black patinas could be useful in choosing appropriate conservation treatments and in the monitoring of stone colonization after the restoration interventions.

Importance of subaerial biofilms and airborne microflora in the deterioration of stonework: a molecular study

The study characterized the sessile microbial communities on mortar and stone in Milan University's Richini's Courtyard and investigated the relationship between airborne and surface-associated microbial communities. Active colonization was found in three locations: green and black patinas were present on mortar and black spots on stone. Confocal laser scanning microscopy, scanning electron microscopy and culture-independent molecular methods revealed that the biofilm causing deterioration was dominated by green algae and black fungi. The mortar used for restoration contained acrylic and siloxane resins that could be used by microorganisms as carbon and energy sources thereby causing proliferation of the biofilm. Epifluorescence microscopy and culture-based methods highlighted a variety of airborne microflora. Bacterial and fungal counts were quantitatively similar to those reported in other investigations of urban areas, the exception being fungi during summer (1–2 orders of magnitude higher). For the first time in the cultural heritage field, culture-independent molecular methods were used to resolve the structure of airborne communities near discoloured surfaces, and to investigate the relationship between such communities and surface-associated biofilms.

Orientation affects Trentepohlia-dominated biofilms on Mayan monuments of the Rio Bec style

The microbial composition of red and black patinas associated with representative buildings from the Mayan sites of Becán, Chicanná and Hormiguero (Campeche, México) was studied. Algae and cyanobacteria were the prevalent microbial groups; the alga Trentepohlia and the coccoid cyanobacterium Gloeocapsa were dominant in terms of biomass. Orientation of buildings played a key role in the spatial distribution of these biological patinas. Irrespective of the site, red patinas, whose coloration was due to the presence of carotenoids (beta carotene and luteine), as evidenced by HPLC, were predominantly associated with North- and East-facing walls, or on otherwise orientated sites if under the influence of tree canopies or monument architecture. In contrast, extensive black patinas were mainly observed on South and West-facing walls. A GIS-based assessment of total solar irradiance for the year 2010 at the site of Becán showed that in general North and East facing walls of monuments received significantly lower levels of radiation, suggesting that the major impact of orientation is to affect incident levels of damaging solar radiation, ensuring higher availability of water for Trentepohlia colonization in low-irradiance areas. Dehydration- and UV-resistant cyanobacteria form dark patinas in more exposed regions. The influence of orientation on biofilm formation on limestone at these sites is briefly discussed.

Recognition of post-harvest processing of algarrobo (Prosopis spp.) as food from two sites of Northwestern Argentina: an ethnobotanical and experimental approach for desiccated macroremains

Ethnobotanical and experimental approaches were used to: (a) analyse modern Prosopis (algarrobo) food production at the Hualfin valley (Catamarca Province, Argentina) in order to establish food production and processing patterns; and (b) characterise the qualitative and quantitative morphological attributes of the food products and residues that may reach the archaeological record as macrobotanical remains. These approaches were applied to the study of archaeobotanical remains from two archaeological sites from the Argentinean Northwest (Huachichocana and Puente del Diablo). It was concluded that the analysis of Prosopis macrobotanical remains potentially allows the identification of intermediate and final products, by-products and residues of different food/drink preparations. Patay (bread) is the only final product that can be confirmed, but only if the bread itself is recovered. The other algarrobo preparations are jam and beverages and therefore do not leave records. The proportions of fragmented seeds, seeds with fissured testas and endocarps may indicate the production of unrefined and refined flour. Anapa (beverage) and aloja (alcoholic beverage) residues are characterised mainly by a rolling or folding of the epicarp or testa (also by the loosening of the testa). Aloja can be distinguished from anapa only if certain processes, such as the use of hot water and the chewing of the pods, were used, which produced diagnostic characteristics such as thick black patinas on endocarps or heavily twisted fine threads of epicarp fibres. Arrope (syrup) residues are identified by the presence of closed endocarps with thin black patinas and twisted ribbons of epicarp. Flour- and aloja-making were recognised from Huachichocana III contexts and anapa and flour production at Puente del Diablo.

Estudio arqueométrico y evaluación del deterioro de los materiales cerámicos de la fachada de la iglesia de Santa Maria del Carmine (Pavía, Italia)

We performed an archaeometric study of the ceramic materials from the facade of the church of Santa Maria del Carmine in Pavia (Italy). We obtained useful information about the firing temperatures, the provenance of raw materials and the type of oven used. The ceramics used in the facade are mineralogically rich in quartz, feldspar and phyllosilicates, and newly formed calcium silicate phases were detected in some samples. Microtextural observations revealed the presence of incipient reaction rims, phyllosilicate sintering and partial vitrification of the matrix. Ceramics show high porosity (32 to 45%) and pore sizes of between 0.4 and 1.3 µm. Our study of the different types of decay collected on the facade of the church (green and black patinas and efflorescences) revealed the presence of gypsum, whewellite, thenardite and moolooite.

Petrographic, biological, and chemical techniques used to characterize two tombs in the Protestant Cemetery of Rome (Italy)

In this multidisciplinary contribution, several diagnostic tests were carried out in order to characterize the stone materials, forms of alteration, and protective products applied in the past to two monumental tombs located in the Protestant Cemetery of Rome (Italy). The Protestant Cemetery is a very important historic site, and has been included in the List of 100 Most Endangered Sites in the World since 2005. In this work, two of its tombs were studied: those of Karl (or Charles) Brjullov, a Russian painter who lived in the first half of the nineteenth century, and of Lady Elisa Temple, wife of the artist Sir Grenville Temple. The tombs are both made of white marble and travertine, and the same forms of alteration and degradation, such as blackish biological patinas, black crusts, and chromatic alterations, were found on both monuments. Petrographic analysis of the different lithotypes made it possible to determine textural characteristics, evaluate the state of preservation, and formulate some hypotheses about their provenance by means of oxygen and carbon isotopic ratios, and evaluation of maximum grain size (MGS) and shape preferred orientation (SPO) of calcite grains. Laboratory culture analysis identified autotrophic species and, in some cases, black patinas caused by fungal species were found. Lastly, Fourier transform infrared spectroscopy (FT-IR) revealed that some synthetic protective products had been used in previous, undocumented restoration processes on some portions of both graves.

Organic Patinas on Small Bronzes of the Italian Renaissance

Previous articleNext article No AccessOrganic Patinas on Small Bronzes of the Italian RenaissanceRICHARD E. STONERICHARD E. STONE Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Metropolitan Museum Journal Volume 452010 Sponsored by the Metropolitan Museum of Art Article DOIhttps://doi.org/10.1086/met.45.41558056 Views: 22Total views on this site Citations: 1Citations are reported from Crossref Copyright © 2010 The Metropolitan Museum of ArtPDF download Crossref reports the following articles citing this article:Marc Aucouturier, François Mathis, Dominique Robcis Les bronzes noirs antiques – nouvelles observations et mécanismes de création, Technè , no.4545 (May 2017): 114–123.https://doi.org/10.4000/techne.1345

Colourful Corrosion: Black Bronze and its Enigmatic Patina

Introduction ‘Black bronze’ is a modern term for ancient bronze artefacts that show a fine, black patina. A patina is an external, physical layer that develops on an object, either artificially or naturally, often lending the object a unique colour. The aim of my 2007-2008 research was twofold: (1) to identify the composition of the black patina for different black bronze corpora and (2) to determine whether the patina developed artificially or naturally in each case. This report will discuss my research into the Greek and Roman corpora of black bronze as well as Chinese black bronze mirrors. Besides these artefacts, I explored several other black bronze corpora including Japanese shakudo and Egyptian statuettes. Through an examination of black bronze artefacts and an extensive literature review, I have concluded that black patinas arose on archaeological bronze by a variety of methods. Furthermore, scholars must work from artefacts, and not from texts, to draw conclusions about black bronze.

Chemical composition and origin of black patinas on granite

Black patinas from the surfaces of granite outcrops (including some with engravings) and granite buildings were analysed. Rock samples were also taken from areas of the same surfaces where there were no black patinas. The constituent elements of the granite rocks, elements of essentially biological origin (C, N, H) and other minor elements, including some typical from pollution, were all determined. The ratios between the concentrations of each element in the patinas and in the corresponding rock samples without patina were calculated in order to determine which elements form the patinas. The data were then examined by hierarchical cluster analysis and principal components analysis to establish the factors that determine the differences between samples. It was found that the elements that differentiate the patinas from the samples of rock without patina are those unrelated to granite, which indicates that, at least from a geochemical point of view, the rocky substrate does not affect patina formation. In all patinas analysed, the concentrations of carbon were higher than in the corresponding samples without patina; there were also relatively higher concentrations of sulphur, phosphorus, chlorine, calcium, etc. in some patinas, depending on the situation of the outcrop or monument.

Diagnostics, deterioration and provenance of stone materials from the Jefferson Page tomb (Non-Catholic Cemetery of Rome, Italy)

The monumental tomb of Jefferson Page, an officer in the American Navy, was built in 1899 and is located in the Non-Catholic Cemetery of Rome (Italy). This study presents complementary diagnostic studies characterizing the stone of the tomb and the weathering and decay phenomena it has undergone. The monument is made of a single type of whitish marble, variously veined and often covered with black patinas. Petrographic, isotopic and LA-ICP-MS analyses attribute the marble to the Carrara district. SEM/EDS and microbiological analyses indicate that the black patinas are due to cyanobacterial autotrophic and fungin heterotrophic colonization. Fourier-transform infrared spectroscopy revealed the presence of organic material on some portions of the tomb, due to undocumented restoration carried out with a mixture of marble powder and a polyester resin.

The effect of coal and diesel particulates on the weathering loss of Portland Limestone in an urban environment

Due to reductions in domestic usage, legislation and changes in fuel use, coal derived particulates in the UK urban atmosphere have been significantly reduced. However, a large increase in road usage and an expansion in the use of diesel engines, has meant that the majority of particulates, now present in the urban atmosphere, originate from vehicle exhausts. Particulate matter, resulting from coal combustion, has been recorded as being present in black patinas observed on some historic stone buildings and monuments and has been associated with accelerated weathering of stone surfaces as a result of enhanced gypsum formation. In contrast, the effects of particulates resulting from vehicle exhaust on stone are much less understood. To investigate this, a comparative study was undertaken using the technique of microcatchments under ambient atmospheric conditions. This compared the elemental composition and volume of precipitation runoff from Portland Limestone coated with three different particulate treatments. Treatments consisted of coal and diesel particulates, both separately and in combination. Combining these treatments attempts to investigate any synergistic effects that may occur when coal derived particulates are overlain by layers formed by particulates from more contemporary sources. It was found that diesel-coated samples were much darker in appearance and showed a significant reduction (P<0.05) in the overall rate of weathering loss when compared to untreated samples. Microcatchment runoff volume was reduced from diesel-coated Portland Limestone compared to untreated stone. Enhanced surface temperatures may be increasing the rate of moisture loss from the pore network between rainfall events. Since, generally, the pores must be full before runoff can occur, the reduction may be due to the differential volume of empty pore space between diesel-coated and untreated Portland Limestone.

Effect of low and high fluence on experimentally laser-cleaned sandstone and marlstone tablets in dry and wet conditions

The eligibility of laser cleaning is tested on regionally specific sculptural stones. Marlstone and sandstone represent the most common building, architectural and sculptural stones employed in the Czech Republic since the Romanesque period. These stone types differ greatly from the marbles on which positive results have been obtained using laser cleaning. Experimental samples were prepared by sawing rock cores. Artificial blackening of samples’ surfaces simulates natural black patinas. The experimental laser cleaning was conducted using Nd:YAG commercial laser (Laserblast 50) at two different fluences—the low one corresponds to the minimum operating capability of the equipment, and the high fluence represents the maximum operating mode of the equipment (i.e. in the ordinary operating range of the equipment). The samples were cleaned under dry and wet conditions. Use of a high fluence resulted in cratering/spalling that is discussed in terms of rock mineralogical composition (presence of clay minerals), adsorption of moisture on clay minerals and physical properties (porosity). Tensional fracturing (evidenced by scanning electron microscopy) along the cleaned surface is the main mechanism of sample destruction due to the vaporization of adsorbed moisture and due to the different elasticity of present rock-forming minerals. Observed discoloration due to high fluence and insufficient cleaning effect of low fluence present other problems encountered.

Determination of elemental and organic carbon on damaged stone monuments

An analytical methodology was developed for the discrimination and evaluation of the different types of carbon matter, particularly carbonate, elemental and organic carbon, present on monuments and historical buildings, due to interaction between materials and atmospheric pollution. With this aim samples of black patinas were analysed by a procedure consisting of three different steps. Total, noncarbonate and elemental carbon were measured by combustion-chromatographic CO 2 determination: C t was obtained by burning the bulk samples (step 1), while C nc and C e were quantified after elimination of C c with acid treatment (step 2) and elimination of C o by means of alternate attacks, followed by centrifugation, with concentrate acid and base solutions at high temperature and pressure (step 3); the carbonate carbon and the organic carbon were then calculated. Furthermore, for a complete sample characterization, oxalate, acetate, formate and the main anion contents were detected by ion chromatography. The methodology was also tested on standard samples containing the same carbon species as the black crusts. The results obtained indicate that this approach satisfactorily distinguishes between elemental and organic carbon and allows reliable elemental carbon determination at the ppm level in black damage crust samples from historic monuments and buildings.

Nature and decay effects of urban soiling on granitic building stones

A detailed microscopical and chemical examination by SEM + EDAX, XRD and PyGC-MS of black patinas coating the surfaces of urban granitic monuments in Aberdeen and Dublin has revealed a variety of decay features together with a complex chemical composition. Beside sulphate-rich thick patinas composed of a framework of gypsum crystals in which both particulate and gaseous inorganic/organic pollutants are deposited and which are similar to gypsum crusts developing under polluted atmospheric conditions on calcite-bearing stones, thinner, gypsum-free, black surface layers made up of particulate matter embedded in a fine-grained, iron-rich matrix are commonly found. These soiling layers show, relative to the substrate, higher % of P, Ca, S, and Cl. The occurrence of a patina's type against the other is probably controlled by the availability of local SO2 sources. Physical and chemical decay effects on the granitic substrate are more severe when gypsum is present but dissolution and micro fracturing episodes are also observed in iron-rich patinas. The chemical inorganic/organic composition of these surficial layers suggests that pollution induced soiling processes are the main factors resoonsible for their build-up on building facades. On the other hand, microscopic and preliminary chemical evidence does not exclude biological activity as an important agent in the development of iron-rich thin black layers.

Investigation of mortar and stone deterioration in the victoria memorial, calcutta

The impressive Italian Renaissance architecture in Calcutta known as the Victoria Memorial has deteriorated noticeably over the last decade. As this has become a major cause of concern, a detailed microstructural investigation of the damaged parts was undertaken to establish the cause of deterioration. This study shows that protracted absorption of pollutants and hydratable salts has given rise to crystallization damage to the sandstone; the carrier substance is moisture. Separation of mortar joints has also occurred, and biological activity has resulted in the deposition of black and greenish patinas on the marble exterior and mortar joints. Copious deep-green patinas of copper sulfate have developed in places where copper plates were used within the structure, causing the building considerable loss of aesthetic beauty.

Non-carbonate carbon content on black and white areas of damaged stone monuments

The carbon present in the black and white areas of stone monuments in nine sites of northern and central Italy has been studied. The samples collected were analysed for their non-carbonate carbon (Cnc) and the percentages of gypsum and carbonates were determined. Elemental analyses of black patinas were also performed. Cnc was found to be mainly of atmospheric origin and is proposed as a quantitative index of the carbonaceous particles embedded within damaged layers. Cnc shows a direct correlation with the concentration of gypsum (the main deterioration product) and an inverse correlation with the carbonate content, originating from the stone. Finally, the elemental analyses revealed the presence of heavy metals, effective catalysts of deterioration reactions.