Microscopic observations of paper and parchment: the archaeology of small objects

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Does the Artemidorus papyrus have multiple lives? Seeking for the answer in the inks through a Raman and PCA analysis

Artemidorus papyrus has been the subject of a longstanding dispute around its authenticity. The 2.5 m long document, presents a multiplicity of writings, on both sides. Some historians support the papyrus’ multiple life hypothesis (PMLH): the different writings appearing on the document, would correspond to three time periods (1st BC–1st AD) called the “three lives of the papyrus”. A possible way to assess whether the document has been written in different eras, is the analysis of the graphic materials employed; a heterogeneous formulation of the inks used throughout the papyrus as a whole, together with a local homogeneity in defined regions, would support PMLH. To unveil this paradigm, we performed an in-depth investigation of the inks on the papyrus, by collecting their Raman spectra on a statistical relevant number of samples belonging to the different regions of the document. We found a wide variety of carbon-based inks that appear to be randomly distributed on the entire surface. Different ordered, disordered, crystalline or amorphous structures might coexist in carbon-based materials, due to the different hybridisations of the carbon. All of the different structures appear as peaks, shoulders or sub peaks that are convoluted in the global spectrum, thus rendering the attribution of Raman peaks as an extremely complex task. In order to support and guide our analysis, we therefore implemented a Principal Component Analysis (PCA) aimed at performing a two-step comparison between the Artemidorus inks Raman spectra and an ample reference spectral library on carbon-based materials that we built specifically for this study. A first PCA screening was used to restrict the analysis for similarity between the experimental spectra and the library of standards to a subset of compounds. It was indeed possible to define a cluster in the Principal Component subspace that contained only a few standards and the whole set of Artemidorus spectra. It is interesting to notice that, among the possibilities in the reference library, our analysis also found two pigments manufactured with modern industrial methods: Carbon black (after 1870) and lampblack (after 1740, modified in 19th c.). A second PCA, performed on the subset of the standard spectra individuated, allowed to highlight the regions of the Raman spectra where the Artemidorus data depict significant differences with respect to their reference standards, thus allowing for a guided deconvolution of the Raman peaks. This study demonstrates that it is not possible to define neat regions on the papyrus that would be identifiable through the usage of different groups of inks, as the same subset of inks is distributed on all of the document. It is therefore impossible to recognise areas of the papyrus where the local usage of specific and region-dependent graphic materials would lead to chronologically distinguishable writings and drawings. This allows us to confute the “three lives hypothesis”

Polyurethane in contemporary Italian design: the case of “Pratoni” in the Triennale Museum, Milan

Since it was synthesised in 1864 by C.A. Wurtz, Polyurethane (PUR) has been widely used for industrial purposes thanks to its great versatility. For this reason, it has been chosen also by designers and artists as a versatile material for the creation of works of art and daily-life objects. PUR, however, is one of the synthetic materials which are subjected to deterioration phenomena in shorter time if compared to historical and traditional art materials. This study takes into consideration three examples of “Pratone”, belonging to the “Multipli” series by the Italian brand Gufram srl and conserved in the Triennale Museum in Milano. “Pratone” is a sofa which reproduces on a higher scale a portion of grass; it was firstly projected in the 1970s using polyurethane foam painted in green colour to recall the natural element. These design objects, although produced in the last 10 years, were already interested by degradation processes. Therefore, they were analysed by optical microscopy, SEM-EDS, FTIR-ATR and TG-DSC techniques in order to obtain information on the compositional materials and the degradation observed and to give information for their conservation in terms of restoration practice and environmental storage conditions. The results pointed out that the three Pratoni were produced using ether-based polyurethane foams, in which additives (such as inorganic fillers, anti-flames retardants, dyestuff, etc) were introduced in the PUR composition. The green paint appeared to be a polyisoprene-based latex. The only difference among the Pratoni consists in the protective layers: two examples were covered by polymetacrilate-based varnish, while the third one was treated with polyetheretherketon (PEEK). The main deterioration processes (yellowing and brittleness of the alveolar structure) were largely due photo-oxidation and humidity problems. This research aims also to stress the importance of studying and understanding what is happening to contemporary art materials and to elaborate preventive conservation plans for their maintenance

Polyurethane in contemporary Italian design: the case of “Pratoni” in the Triennale Museum, Milan

Since it was synthesised in 1864 by C.A. Wurtz, Polyurethane (PUR) has been widely used for industrial purposes thanks to its great versatility. For this reason, it has been chosen also by designers and artists as a versatile material for the creation of works of art and daily-life objects. PUR, however, is one of the synthetic materials which are subjected to deterioration phenomena in shorter time if compared to historical and traditional art materials. This study takes into consideration three examples of “Pratone”, belonging to the “Multipli” series by the Italian brand Gufram srl and conserved in the Triennale Museum in Milano. “Pratone” is a sofa which reproduces on a higher scale a portion of grass; it was firstly projected in the 1970s using polyurethane foam painted in green colour to recall the natural element. These design objects, although produced in the last 10 years, were already interested by degradation processes. Therefore, they were analysed by optical microscopy, SEM-EDS, FTIR-ATR and TG-DSC techniques in order to obtain information on the compositional materials and the degradation observed and to give information for their conservation in terms of restoration practice and environmental storage conditions. The results pointed out that the three Pratoni were produced using ether-based polyurethane foams, in which additives (such as inorganic fillers, anti-flames retardants, dyestuff, etc) were introduced in the PUR composition. The green paint appeared to be a polyisoprene-based latex. The only difference among the Pratoni consists in the protective layers: two examples were covered by polymetacrilate-based varnish, while the third one was treated with polyetheretherketon (PEEK). The main deterioration processes (yellowing and brittleness of the alveolar structure) were largely due photo-oxidation and humidity problems. This research aims also to stress the importance of studying and understanding what is happening to contemporary art materials and to elaborate preventive conservation plans for their maintenance

Oleanolic and ursolic acid in dammar and mastic resin: Isomer discrimination by using ToF-SIMS and multivariate statistics

Triterpenoid resins, such as dammar resin and mastic resin, are natural products used as protective varnishes on paintings. Dammar resin consists of a large amount of triterpenoid molecules including two triterpenic acids: oleanolic acid and ursolic acid. Similarly, mastic resin is a complex blend of terpenoids but containing oleanolic acid. In this paper, high-mass-resolution time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been used to characterize the fragmentation patterns of oleanolic acid and ursolic acid. The hypothesized fragmentation pathways for these triterpenic acids have also been discussed. In order to distinguish between these two structural isomers, principal component analysis (PCA) has been adopted. This multivariate statistical analysis technique permits to identify the characteristic fragments and discriminates between very similar mass spectra. In addition, dammar resin and mastic resin have been characterized. A selection of characteristic peaks from ursolic and oleanolic acids mass spectra has been used to build a dataset for a multivariate analysis to compare triterpenoid resins and triterpenic acids. The results of PCA have revealed that mastic resin is strictly related to oleanolic acid, whereas dammar resin is differentiated by ursolic acid fragments. This study confirms that, in the cultural heritage field, the time-of-flight secondary ion mass spectrometry technique combined with PCA can be a powerful tool to investigate the chemical composition of organic compounds with very complex composition

Polyurethane in contemporary Italian design: the case of “Pratoni” in the Triennale Museum, Milan

Since it was synthesised in 1864 by C.A. Wurtz, Polyurethane (PUR) has been widely used for industrial purposes thanks to its great versatility. For this reason, it has been chosen also by designers and artists as a versatile material for the creation of works of art and daily-life objects. PUR, however, is one of the synthetic materials which are subjected to deterioration phenomena in shorter time if compared to historical and traditional art materials. This study takes into consideration three examples of “Pratone”, belonging to the “Multipli” series by the Italian brand Gufram srl and conserved in the Triennale Museum in Milano. “Pratone” is a sofa which reproduces on a higher scale a portion of grass; it was firstly projected in the 1970s using polyurethane foam painted in green colour to recall the natural element. These design objects, although produced in the last 10 years, were already interested by degradation processes. Therefore, they were analysed by optical microscopy, SEM-EDS, FTIR-ATR and TG-DSC techniques in order to obtain information on the compositional materials and the degradation observed and to give information for their conservation in terms of restoration practice and environmental storage conditions. The results pointed out that the three Pratoni were produced using ether-based polyurethane foams, in which additives (such as inorganic fillers, anti-flames retardants, dyestuff, etc) were introduced in the PUR composition. The green paint appeared to be a polyisoprene-based latex. The only difference among the Pratoni consists in the protective layers: two examples were covered by polymetacrilate-based varnish, while the third one was treated with polyetheretherketon (PEEK). The main deterioration processes (yellowing and brittleness of the alveolar structure) were largely due photo-oxidation and humidity problems. This research aims also to stress the importance of studying and understanding what is happening to contemporary art materials and to elaborate preventive conservation plans for their maintenance

The Use of Polyurethane Foam in Contemporary Italian Design: Case Studies from the Triennale Design Museum in Milan

This paper reports the study of several design objects from the Triennale Design Museum in Milan – all of which are part of the Multipli series by the Italian brand Gufram® – including three examples of a sofa called Pratone, three stone-shaped seats called Sedilsasso e sassi, a coat stand in the shape of a Cactus and the Capitello recliner. All of these design objects were produced at different times from the early 1970s to the present day using “polyurethane foam and washable latex”, and are already showing signs of different degradation processes. In addition to identifying the various material compositions and degradation phenomena that affect these artefacts, in order to develop preventive conservation plans for their future maintenance, our study sought to identify any differences in the materials and manufacturing techniques used to produce the same series over the years and if these differences can be correlated to their state of conservation. Samples of the objects were collected and examined by optical and electron microscopy, FTIR-ATR, XRF and pyGC-MS to obtain information relative to the compositional materials involved (PUR foams, painted layers, varnishes and protective coatings) and the relative degradation processes

The use of polyurethane foam in contemporary Italian design: Case studies from the Triennale Design Museum in Milan

Since it was first synthesised in 1864 by C.A. Wurtz, Polyurethane (PUR) has been widely used for industrial purposes thanks to its great versatility. For this same reason, PUR has also become a popular material for designers and artists in the creation of artworks and every-day objects. However, as a synthetic material that deteriorates more quickly than traditional art materials, PUR has also become the subject of many in-depth scientific studies, and a particular focus in the research of Thea van Oosten and coworkers. In this research project we focused on several case studies from the Triennale Design Museum in Milan – all of which belong to the Multipli series by the Italian brand Gufram® – including three examples of a sofa called the Pratone (which reproduces a patch of grass on a giant scale), three “stone” shaped seats entitled Sedilsasso e sassi, a coat rack in the shape of a red Cactus and the Capitello recliner. All of these design objects were produced at different times during a period which stretches from the middle of the 1970’s up until today’s “polyurethane foam and washable latex” (as reported in the catalogue), and are already showing the results of different degradation processes. In addition to identifying the differing material composition and degradation phenomena which affect these artefacts, so as to develop preventive conservation plans for their future maintenance, our research sought to identify whether there were differences in the materials and manufacturing techniques used to produce the same series over the years and if these differences can be correlated to their state of conservation. To obtain information relative to the compositional materials involved (PUR foams, painted layers, varnishes and protective layers) and the relative degradation processes, micro-samples taken from the objects were analysed using different analytical techniques (vis-UV optical microscopy, XRF, SEM-EDS, FTIR-ATR, Py-GC-MS and TG-DSC). The results indicated that the objects’ PUR inners have different compositions at different production times: the first examples were analysed as TDI (toluene diisocyanate) urethane ethers with polypropylene glycol as the flexible part, while latter objects are composed of TDI- polypropylene glycol urethane ether with the addition of styrene acrylonitrile (SAN). Several additives -being introduced to the polymeric compositions- were identified, such as: butylated hydroxytoluene (BHT) and dioctyldiphenylamine as antioxidants; tris(3-chloropropyl) phosphate, dibutylphthalate (DBP) and dioctylphthalate (DOP) used as plasticizers. In all cases, the painted layers appeared to be a polyisoprene-based latex containing both inorganic and organic pigments, fillers (silica) and extenders (calcium carbonate, gypsum); benzimidazole and benzothiazole- used in the vulcanization process of the isoprene, were detected as well. For the protective layers we found the use of varnishes based on polymetacrilate in the early objects and on polyetheretherketon for the more recent ones. With the help of the owners of Gufram®, we were able to analyse and compare our results in order to align the object’s historical evolution, the reasons behind variations in the production processes and of course, changes in the material composition of the PUR used in these objects, with the aim of acquiring a 360° working knowledge and evaluate the contingent factors which can affect PUR during the ageing process

Raman and time of flight secondary ion mass spectrometry investigation answers specific conservation questions on Bosch painting Saint Wilgefortis Triptych

Raman spectroscopy and time of flight secondary ion mass spectrometry (ToF‐SIMS) were used to answer conservation questions left open after the preliminary analysis performed by the restoration team on the Bosch painting Saint Wilgefortis Triptych, within the project “Bosch in Venice.” In this work, we present the results obtained by combining these two techniques on five cross sections, concerning a detailed study of pigments and bindings degradation processes, the identification of organic components (binders/lakes), and the characterization of restoration products. Raman measurements show the presence of degradation products, such as calomel on the red pigment cinnabar, calcium‐oxalate, in particular weddellite, localized in a not original external layer, and finally lead soaps in several layers of the investigated samples. Although the detection of lead soaps suggests the use of oils as binders, Raman spectroscopy has given no conclusive information about such binders, neither on the possible presence of red lakes, suggested by independent UV observations. Complementary ToF‐SIMS investigations have instead revealed the presence of lead palmitate and stearate in the painting layers along with miristic, palmitic, oleic, and stearic acids, thus confirming the use of an oil medium, likely linseed oil. Additionally, ToF‐SIMS shows the presence of polydimethylsiloxane, likely from a previous restoration treatment in the 1990s, in the external layer of the investigated cross sections. Due to experimental difficulties during the analysis of the red lake, we can only hypothesize the presence of alizarin