Papers by Johanna Salvant
Nanomaterials
The conservation of textiles is a challenge due to the often fast degradation that results from t... more The conservation of textiles is a challenge due to the often fast degradation that results from the acidity combined with a complex structure that requires remediation actions to be conducted at several length scales. Nanomaterials have lately been used for various purposes in the conservation of cultural heritage. The advantage with these materials is their high efficiency combined with a great control. Here, we provide an overview of the latest developments in terms of nanomaterials-based alternatives, namely inorganic nanoparticles and nanocellulose, to conventional methods for the strengthening and deacidification of cellulose-based materials. Then, using the case of iron-tannate dyed cotton, we show that conservation can only be addressed if the mechanical strengthening is preceded by a deacidification step. We used CaCO3 nanoparticles to neutralize the acidity, while the stabilisation was addressed by a combination of nanocellulose, and silica nanoparticles, to truly tackle th...
It had long been believed that the plastic substrates of László Moholy-Nagy's paintings T1 (1926)... more It had long been believed that the plastic substrates of László Moholy-Nagy's paintings T1 (1926) and Tp 2 (1930) in the collection of the Solomon R. Guggenheim Museum were a phenol formaldehyde resin called Trolitan. Recent investigations using a combination of microscopy and instrumental analysis revealed that these plastics are actually cellulose nitrate filled with a significant proportion of gypsum. The pigments, plasticizers and other organic components were also thoroughly characterized. When considered together with archival information, these characteristics indicate that this material should rather be identified as an industrial plastic called Trolit produced at the same factory as Trolitan: the Rheinisch-Westfälischen Sprengstoff-Fabriken (RWS) in Troisdorf, Germany. This first analytical description of Trolit provides new insights into Moholy-Nagy's unconventional material choices, highlights the remarkably good current condition of the works of art, and shows the importance of using scientific analysis to correctly identify historic plastics instead of relying on trade names for their material identification.
In this paper, we study the problem of automatic identification of pigments applied to paintings ... more In this paper, we study the problem of automatic identification of pigments applied to paintings using hyperspectral reflectance data. Here, we cast the problem of pigment identification in a novel way by decomposing the spectrum into pure pigments. The pure pigment exemplars, chosen and prepared in our laboratory based on historic sources and archaeological examples, closely resemble the materials used to make ancient paintings. To validate our algorithm, we created a set of mock-up paintings in our laboratory consisting of a broad palette of mixtures of pure pigments. Our results clearly demonstrate more accurate estimation of pigment composition than purely distance-based methods such as spectral angle mapping (SAM) and spectral correlation mapping (SCM). In addition, we studied hyperspectral imagery acquired of a Roman-Egyptian portrait, excavated from the site of Tebtunis in the Fayum region of Egypt, and dated to about the 2nd century CE. Using ground truth information obtained using Raman spectroscopy, we show qualitatively that our method accurately detects pigment composition for the specific pigments hematite and indigo.
It had long been believed that the plastic substrates of László Moholy-Nagy's paintings T1 (1926)... more It had long been believed that the plastic substrates of László Moholy-Nagy's paintings T1 (1926) and Tp 2 (1930) in the collection of the Solomon R. Guggenheim Museum were a phenol formaldehyde resin called Trolitan. Recent investigations using a combination of microscopy and instrumental analysis revealed that these plastics are actually cellulose nitrate filled with a significant proportion of gypsum. The pigments, plasticizers and other organic components were also thoroughly characterized. When considered together with archival information, these characteristics indicate that this material should rather be identified as an industrial plastic called Trolit produced at the same factory as Trolitan: the Rheinisch-Westfälischen Sprengstoff-Fabriken (RWS) in Troisdorf, Germany. This first analytical description of Trolit provides new insights into Moholy-Nagy's unconventional material choices, highlights the remarkably good current condition of the works of art, and shows the importance of using scientific analysis to correctly identify historic plastics instead of relying on trade names for their material identification.
InvestIgatIon of the grounds of tasset et L'hôte commercIaLLy prImed canvas 1 | hendriks and Van ... more InvestIgatIon of the grounds of tasset et L'hôte commercIaLLy prImed canvas 1 | hendriks and Van tilborgh 2011, p. 95, note 16: according to the information provided by stéphanie constantin from the 'états cadastraux' of 1876, the shop measured 20 m 2 ; reff 1999, p. 76.
Msurnd : afn dr minimiser k ddterioration des objex culturels il est ndcessaire dz rnieux connait... more Msurnd : afn dr minimiser k ddterioration des objex culturels il est ndcessaire dz rnieux connaite les matiriaux qui les constituent, ainsi qae I'enuironnement qui les entoure. Pour atteindre cet objectif, un programrne de recherche uisant I'identification de sources potentielles de conditions agressiues, tel que les digagements des rnatlriaux utilisds dans les uitrines et les dep|ts dz parti.cules de I'air, est actuellernent en cours. Des coupons maalliques (argrnt, plomb et cuiur) ont dti erposds sous difrrentes conditions dans plusieurs institutions cuburelles. Ils sont censds agir comme des capteurs, qui riagissent raltidernent et sllectiaement anec certains polluants de I'air pour former une couclte superficielle de ternissure. L'analjtse de cette couche par riduction dlectrochirnique renseigne sur h nature chimique des produits formls ainsi que sur /a uitesse dz ooissance pour un enuironnement donnd. De cette fagon, non seulement hs 4bments nocifi peuuent 6ne idzntifds, mais il est igabment possible d'daaluer leur ffit synergitique en prdsence d'aunes polluants et dz I'humiditi. Des rlsubats priliminaires seront pry'sentds et discutis en considirant dcs standards existants. l\ f algr6 les soins apportds aux objets IVl.,rltutels pour les conserver dans les meilleures conditions possibles, plusieurs euvres m6talliques exposdes dans les musdes se ddgradent progressivement par interaction avec leur environnement. IJne am6lioration des conditions de conservation est alors ndcessaire mais est rendue exrdmement difiicile par la complexitd et la diversitd des paramttres influengant le vieillissement de l'objet (polluants prdsents, taux d'hurnidit6, temp6rature). Une caract€risation pr€li minaire de I'environnement oil sont expos€s les objets culturels mdtalliques, prenant en compte les divers facteurs environnementalx, s'avtre donc indispensable. Pour proc6der ) cette 6valuation, &verses 6tudes ont 6t€ r6alis6es pour identifier les polluants agrbssifs pour un matdriau donn6, conduisant I la d€finition des listes de n combinaisons interdites n, tel que plomb-bois (acides organiques), argentJaine (composds soufr€s) (Hatchfield, 2002). Par la suite, on a tenr6 d'6tablir des seuils de concentration d'un polluant donn6 (CH3COOH, HzS, par exemple) en dessous desquels le risque de ddt6riora' tion d'un matdriau est minime (T6ueault, 2000). Cependant, dans la pratique, la question qui se pose ne concerne pas seulement la tr8s co0teuse ddtermination de la concentration de certains polluants, rnais surtout l'dvaluation des multiples interactions possibles avec d'autres variables atmosphdriques et, finalernent, I'interprdtation de toutes ces donndes (V'atrs, 1999). AJin de considdrer I'ensemble des paramdtres, une alternative ad6quate consiste ) exposer des capteurs m€talliques, qui rdagissent avec I'ensemble des 6l6ments de I'environnement i la fois, consid6rant ainsi leur synergie (Costa, 2006). Les alliages les plus udlisds sont ceux en argent et en cuivre, en raison de leur sensibilit6 aux diftrenrs facteurs environnementaux, ainsi que de leur facilit6 d'analyse. hs capteurs m€talliques ne pr6tendent pas €tre reprdsentatifs des euvres culturelles i c6t€ desquelles ils ont'6t6 placds et qui sonr, bien souvent, constitudes par des alliages divers et inconnus, Dans la pratique ils sont placds dans des zones dont il est important de connaitre la qualird de I'environnemenr, tel que des vitrines ou encore des salles d'exposition. La dur6e de I'exposition d6pend de I'agressivit€ de I'environnement et de la sensibilit6 de la mdthode qui sera uti-lis€e pour I'dvaluation. Toutes les mdthodes sont basdes sur l'6valuation de 99 CHR rEcHNreuE N" l5 la quantit6 de m6tal qui a 6t6 oxyd€ par les polluants pendant I'exposition et qui peut 6tre 6valude par les difftrences de masse (pesage avant et aprts I'exposition), par mesure de la r6sistivit6, €lecrique (qui augmente en fonction du degr6 d'oxydation) et par l'dquivalence rnasse-charge (r6duction 6lectrochimique des produits formds I la surface). Les rdsultats sont exprim€s en tant que quantit6 de mdtal oxydd : charge (C), masse (g) ou dpaisseur (pm) par unit€ de surface et par pdriode de temps.
Background: In this study, an enameled glass mosque lamp in the Brooklyn Museum collection is inv... more Background: In this study, an enameled glass mosque lamp in the Brooklyn Museum collection is investigated to elucidate the origin and date of production of each of its components—the body, handles, wick-holder, and foot—to establish whether the lamp was produced during the Mamluk period (13th–14th century) or is a 19th-century Euro-pean creation. Results: Using X-ray fluorescence spectrometry and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM–EDS), the body, handles, and wick-holder were found to exhibit identical composition. The lamp's foot, however, presents a dissimilar composition, one significantly richer in sodium, magnesium, and potassium. The matrix compositions, colorants, and opacifiers of the body's enamel decorations were characterized by SEM–EDS and Raman spectroscopy analyses and compared with Mamluk and 19th-century production. Conclusions: The lamp's body, handles, and wick-holder were produced using the same type of glass, one likely incorporating a plant ash flux typical of medieval Islamic glass. Materials composing the body's enamel decorations are consistent with Mamluk production. The foot's distinct composition indicates that it is a later addition to the object. Combining the analytical, stylistic, and historical evidences, this glass lamp can now be identified as a Mamluk example, one of few comprising an integral wick-holder. The presence of a wick-holder is discussed and connected to the small size of the lamp. Details informing understanding of the lamp's manufacture are also included. The implications of these new findings on the object's conservation treatment and display are discussed in the context of the upcoming reinstallation of the Arts of the Islamic World gallery at the Brooklyn Museum.
The use of the pigment Egyptian blue is investigated on a corpus of fifteen mummy portraits and R... more The use of the pigment Egyptian blue is investigated on a corpus of fifteen mummy portraits and Roman-period paintings from Tebtunis, Egypt, housed in the Phoebe A. Hearst Museum of Anthropology at the University of California, Berkeley. Egyptian blue has a strong luminescence response in the near infrared that can be exploited to created wide-field images non invasively showing the distribution of the pigment on a work of art. A growing body of publications in the last decade highlights the increasing use of this tool and its sensitive detection limits. However, the technique is not wavelength specific. Both excitation and emission occur in a broad range. Although Egyptian blue has a strong emission in the NIR, a myriad of other compounds may emit light in this spectral region when excited in the visible. The limited number of studies including complementary analysis to verify the presence of Egyptian blue does not allow its identification on the basis of NIR luminescence alone. Through the use of in situ X-ray fluorescence and X-ray diffraction, and scanning electron microscopy/energy-dispersive spectroscopy of cross sections, this paper confirms the identification of Egyptian blue by NIR luminescence in unexpected areas, i.e., those not blue in appearance.
InvestIgatIon of the grounds of tasset et L'hôte commercIaLLy prImed canvas 1 | hendriks and Van ... more InvestIgatIon of the grounds of tasset et L'hôte commercIaLLy prImed canvas 1 | hendriks and Van tilborgh 2011, p. 95, note 16: according to the information provided by stéphanie constantin from the 'états cadastraux' of 1876, the shop measured 20 m 2 ; reff 1999, p. 76.
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Papers by Johanna Salvant