Binding Medium Analyses of Paintings by Alonso Sanchez Coello and El Greco

No abstract available

Influence of Sunlight during Harvest on the Oxidation and Yellowing of Natural Mastic Resins Used as Varnishes on Artwork

The natural resin mastic, composed largely of triterpenes, is used as a varnish on artwork. This study investigates the influence of light on the autoxidation and yellowing of mastic, both during harvest and after application as a film. The nature of photoinitiation reactions is considered, as is the propagation of oxidative processes in both light and darkness. Oxidation, radical content and yellowing were studied by graphite-assisted laser desorption mass spectrometry, EPR and UV/VIS spectrometry, respectively. Exposure to sunlight during harvesting is found to strongly affect the resin. The radical content increases dramatically, and oxidation is accelerated. These differences are also observed during artificial aging under a range of conditions. Mastic that is harvested without exposure to sunlight deteriorates less quickly in all respects. This is attributed to lack of sunlight-generated radicals and/or labile radical precursors, which are very long-lived in the viscous resin or solid film. Remarkably, radicals are found to be nearly as prevalent in dark-aged films as those aged in light. Oxidation in the dark is also nearly as fast as with continuous light exposure. These results suggest that dark and light aging are not fundamentally different, in contrast to the conventional model

A holistic view on the role of egg yolk in Old Masters’ oil paints

Old Masters used paints containing mixtures of oils and proteins, but we lack an understanding on how and why proteins were used. Here, the authors use egg yolk in combination with two pigments to evaluate how different repartition of proteinaceous binder can be used to control the flow behaviour as well as drying kinetics and chemistry of oil paints

Aging and yellowing of triterpenoid resin varnishes - Influence of aging conditions and resin composition

The aging of natural triterpenoid resins used as varnishes on paintings is still insufficiently understood. Although progress has been made, questions concerning the aging pathways in light vs. darkness, or the correlation of oxidation with yellowing, remain open. The influence of aging conditions, primarily the amount of light, but also resin composition, on the aging process were investigated. The aging reactions are followed using a variety of mass spectrometric and spectroscopic techniques. Aging processes in dammar and mastic varnishes are shown to be more dynamic and extensive than had generally been believed. In unaged bulk resins, large quantities of radicals develop within weeks after application as a varnish, due to the greatly increased surface-to-volume ratio. This is true for all aging conditions, including aging in darkness, and is accompanied by considerable oxidation as well. After a few months, most of the initial triterpenoids are oxidized. Natural aging in light and darkness leads to the same main aging products. All these findings point to the conclusion that aging largely proceeds by the same pathways in both light and darkness, mainly autoxidation. Without light, enough radicals are formed to maintain extensive autoxidation, although more slowly. Thus, differences between light and dark aging mechanisms are much smaller than often believed. In mastic, the absence of the polymeric constituents is found to enhance oxidation, but reduce yellowing. It appears that the polymer acts as a natural radical stabilizer, favoring the pronounced intrinsic yellowing tendency of mastic. The manipulation of resin composition might lead to improved aging properties of triterpenoid resin varnishe

R Zenobi., Aging and yellowing of triterpenoid resin varnishes - Influence of aging conditions and resin composition

Abstract The aging of natural triterpenoid resins used as varnishes on paintings is still insufficiently understood. Although progress has been made, questions concerning the aging pathways in light vs. darkness, or the correlation of oxidation with yellowing, remain open. The influence of aging conditions, primarily the amount of light, but also resin composition, on the aging process were investigated. The aging reactions are followed using a variety of mass spectrometric and spectroscopic techniques. Aging processes in dammar and mastic varnishes are shown to be more dynamic and extensive than had generally been believed. In unaged bulk resins, large quantities of radicals develop within weeks after application as a varnish, due to the greatly increased surface-to-volume ratio. This is true for all aging conditions, including aging in darkness, and is accompanied by considerable oxidation as well. After a few months, most of the initial triterpenoids are oxidized. Natural aging in light and darkness leads to the same main aging products. All these findings point to the conclusion that aging largely proceeds by the same pathways in both light and darkness, mainly autoxidation. Without light, enough radicals are formed to maintain extensive autoxidation, although more slowly. Thus, differences between light and dark aging mechanisms are much smaller than often believed. In mastic, the absence of the polymeric constituents is found to enhance oxidation, but reduce yellowing. It appears that the polymer acts as a natural radical stabilizer, favoring the pronounced intrinsic yellowing tendency of mastic. The manipulation of resin composition might lead to improved aging properties of triterpenoid resin varnishes

Materials and Techniques of Polychrome Plaster Sculpture in the Harzvorland, Germany (c. 1200-1240): The Choir Screens of Halberstadt and Eilenstedt

No abstract available

Materiali d'artista. L'atelier del pittore nell'Otto e Novecento

I materiali dagli atelier degli artisti dell\u2019Otto e Novecento, oggi conservati e spesso musealizzati, pongono questioni metodologiche. Tali oggetti possono essere utili strumenti di indagine tecnica sul fare dell\u2019artista nell\u2019Otto e Novecento, grazie a molteplici approcci possibili: la ricostruzione e mappatura degli oggetti, le informazioni fornite dallo studio delle fonti (carteggi, taccuini di artisti, trattati) e dei prodotti disponibili sul mercato, lo studio della rete di rapporti fra gli artisti e le case produttrici di colori, la rappresentazione coeva e l\u2019odierna catalogazione di tali materiali

Imaging spectrum of Bing–Neel syndrome: how can a radiologist recognise this rare neurological complication of Waldenström’s macroglobulinemia?

Objectives: Bing-Neel syndrome (BNS) is a rare neurological complication of Waldenström's macroglobulinemia. The aim of this study is to describe the spectrum of radiological manifestations of this syndrome and their prevalence in order to facilitate its early diagnosis. Methods: Twenty-four patients with BNS were diagnosed between 1994 and 2016 in eight centres in France. We retrospectively examined the medical records of these patients as well as the corresponding literature, focusing on imaging studies. Recorded data were statistically analysed and radiological findings described. Results: The mean age of our patients was 62.4 years (35-80 years). The vast majority of patients were men, with a male to female ratio of 9:1. Findings included parenchymal or meningeal involvement or both. The most common finding was leptomeningeal infiltration, either intracranial or spinal, with a prevalence reaching 70.8%. Dural involvement was present in 37.5% of patients. In 41.7% (10/24) of patients, there was parenchymal involvement with a higher prevalence of brain comparing to medullar involvement (33.3% and 23.1% respectively). High T2 signal of the parenchyma was identified in 41.7% of patients and high signal in diffusion was evident in 25% of them. Intraorbital or periorbital involvement was also detected in four cases. A proposition regarding the appropriate imaging protocol completed our study. Conclusion: BNS's diagnosis remains challenging. Central nervous system MRI findings in the setting of known or suspected Waldenström's macroglobulinemia appear to be highly suggestive of BNS and appropriate imaging protocols should be implemented for their depiction. Key points: • Diagnosis of Bing-Neel syndrome (BNS) remains challenging and recent expert recommendations include MRI in the diagnostic criteria for the syndrome. • The most common radiological manifestations of BNS are leptomeningeal/dural infiltration or parenchymal involvement of brain or spinal cord, but many atypical forms may exist with various presentations. • Appropriate imaging protocol for BNS should include enhanced MRI studies of both brain and spine.</p