SCIENTIFIC INVESTIGATION OF AN IMPORTANT CORPUS OFPICASSO PAINTINGS IN ANTIBES: NEW INSIGHTS INTOTECHNIQUE, CONDITION, AND CHRONOLOGICAL

SEQUENCE

FRANCESCA CASADIO, COSTANZA MILIANI, FRANCESCA ROSI, ALDOROMANI, CHIARA ANSELMI, BRUNO BRUNETTI, ANTONIO SGAMELLOTTI,

JEAN-LOUIS ANDRAL, AND GWÉNAËLLE GAUTIER

Conservation Department, The Art Institute of ChicagoDipartimento di Chimica, Istituto CNR di Scienze e Tecnologie Molecolari (ISTM-CNR)

Dipartimento di Chimica, Centro SMAArtMusée Picasso, Antibes

Independent conservation scientist

The Musée Picasso in Antibes (France) houses a unique collection of paintings and works on paper by PabloPicasso, completed during the fall of by the artist, working on the same premises occupied today by theMuseum. Picasso painted with readily available materials including oleoresinous enamel paints, fibrocement,wood panels, paper sheets, and re-used canvases. In this paper the results of an extensive campaign of scientificanalysis of of these works with both non-invasive and micro-invasive techniques are described. The project elu-cidated the full palette of the paintings, dispelling myths about their execution solely with the renowned brand ofenamel paint Ripolin. The effective combination of elemental and spectroscopic methods of analysis enabled finediscriminations among various types of white enamel paint used by Picasso in Antibes. Because the artist appearedto have used such paints in chronological sequence, the precise identification of the type of white paint present oneach of the works allowed the assignment of revised dates to some of the undated paintings. Important new infor-mation on surface coatings of wax and modern polymeric varnishes, as well as the widespread presence of metalsoaps including zinc oxalates, was also uncovered.

KEYWORDS: Picasso, oleoresinous paint, enamel paint, Ripolin, spectroscopic analysis, Antibes

. INTRODUCTION

The Musée Picasso in Antibes (MPA) has among itsimportant holdings a unique collection of paintingsand works on paper, executed by Picasso betweenSeptember and November , and enhanced in with an additional monumental painting(Ulysses and the Sirens, MPA inventory number..). All the works were painted on-site by theartist while he was residing in the south of France.Picasso painted in the top floor of the building wherethe collection is now displayed, perched on a cliff over-looking the Mediterranean Sea. This remarkable unityof time and place endows the collection with historicalimportance. It also makes it an unparalleled locationfor the investigation of Picasso’s technique at apivotal moment of renovation in the artist’s career:

right at the close of World War II and with a youngnew companion by his side. A detailed photographiccampaign carried out by Michel Sima, a sculptor,photographer, and friend of Picasso recently returnedto France from concentration camps, documents theartist at work (Sima et al. ). Of notable interestin the photographs is the widespread presence ofnumerous cans of paints and, conversely, the apparentlack of rolled-up tubes of artist’s paints. These photo-graphs as well as documentary evidence (Gilot andLake ) seem to support the notion that Picassoavailed himself of readily available materials for hisstudio by the sea: fibrocement panels (a constructionmaterial available in thin sheets made of cementreinforced with asbestos fibers), plywood supports,cans of paints acquired at the local drugstore, and afew painted canvases reclaimed from the storage

© American Institute for Conservationof Historic and Artistic Works DOI: ./Y. Journal of the American Institute for Conservation , Vol. No. , –

vaults of what was then a local historical and archaeo-logical museum, and is presently the Musée Picasso inAntibes (Dor de la Souchère ; Giraudy –;Andral ). The pursuit of a very specific aestheticand the unique technical properties of enamel paints

have been suggested as motivations for the artist’s useof these materials. Additionally, Picasso might havechosen enamel paints in Antibes because they wereespecially formulated to display enhanced durabilityin a marine environment (Gilot and Lake ). TheAntibes collection represents the prime site for theexploration of the artist’s use of enamel paints alsobecause anecdotal evidence led to a longstandingassumption that all the works in Antibes were paintedwith Ripolin. Giraudy (–, v) prominentlyillustrated a Ripolin color chart when presenting thefirst technical examination of the works in the collec-tion, implying that the colors of Ripolin describedtherein were the paints making up Picasso’s palette inAntibes. Thus, through most of its history the corpusof the collection has been variously identified as oil,oil and Ripolin, oil and enamel, oil and alkyd (glycér-ophtalique), and variations thereof (Giraudy –; Casadio and Gautier ). However, the availablehistorical photographs as well as receipts for paintingmaterials in the Museum archives suggest the use ofother types of paint. Specifically, receipts in theMuseum archives dated between September andOctober document purchases of differentcolored paints: Zinc Green (Vert de Zinc, francs),Prussian blue (Bleu de Prusse, francs), Chariotblue (Bleu Charron, francs), and a can of Yellowocher (Ocre Jaune, gr. franc). Additionally acan of white “zincolac” (zincolac blanc, kg, francs), and several other rather non-descript chargesfor white paint (Peinture blanche) and Marine drug-store paint (Peinture Droguerie Marine), or white drug-store paint (Peinture Blanche Droguerie), aredocumented from one of Picasso’s suppliers inAntibes, the Droguerie de la Marine. Also documentedare the acquisition of the fibrocement supports andseveral purchases of drier (siccatif), as well as brushesand black soap (savon noir) to clean them.The main objective of this work was to determine if

and for which artworks the use of actual paints of thebrand Ripolin could be confirmed, if the latter wereof the oleoresinous or alkyd type, and if other typesof paints could be identified. Additionally, anothergoal of this study was to determine which of thepaints that appear visually similar on the surface ofthe works actually have the same composition, indicat-ing use of ready-mixed enamel paint from the same can.In order to address these questions, this paper focuses

on the in-depth examination of a selection of works,including four on paper. The artworks were thoroughlyinvestigated with a multi-analytical approach that

involved the use of non-invasive techniques combinedwith the micro-invasive analysis of a limited numberof samples (table ). The availability of samples(new and archival, as explained below and detailed intable ) for the artworks allowed refining and some-times clarifying the characterization of some of thepainting materials obtained with the non-invasive tech-niques. New sampling was kept at a minimum becauseof the remarkably good condition of the artworks,mostly due to the minimal traveling and loan historyof the collection. The several non-invasive techniquesused allowed the characterization of a large numberof works in detail, testing several areas of the paintings,so as to gain truly representative materials identifi-cation, which is not possible through individual pointanalysis alone (Miliani et al. ). Importantly, thepainted surfaces have for the most part been preservedas the artist left them, that is, generally unvarnished,offering perfect experimental conditions for in situinvestigation with non-invasive techniques.Valuable preliminary information exists on the

materials and methods of Picasso in Antibes, includingan extensive campaign of infrared reflectography, alimited number of x-ray images and preliminarypigment and media identification (Giraudy –, v). This study significantly expands the scopeof those preliminary investigations, thoroughly docu-menting the entire color palette of the Antibes works,clarifying the extent of actual Ripolin usage, and forthe first time also addressing the characterization ofthe works on paper. Furthermore, because theMuseum does not have a staff conservator and its docu-mentation is sometimes incomplete, this work addsvaluable information on the condition as well as pasttreatment of some of the works. Additional results ofan extensive campaign of analysis spanning the entiretyof the collection are reported elsewhere (Picasso ).

. MATERIALS AND METHODS

The non-invasive methods of analysis used includedx-ray fluorescence spectroscopy (XRF), fiber-opticFourier transform mid-infrared spectroscopy (MIR),fiber-optic Fourier transform near-infrared spec-troscopy (NIR), fiber-optic UV/visible—near infraredreflectance spectroscopy (UV/Vis-NIR FORS), andUV–Vis fluorescence spectroscopy (UV-Vis Fluo)(fig. and table ). The works examined duringthis campaign are listed in table and include fourworks on fibrocement, five on plywood, four onre-used canvas (previously painted by other artistsand either scraped or directly painted over by Picasso;Giraudy –), and four on paper.Data obtained from the non-invasive investigation

campaign were enhanced by further analysis of microscopic samples. As detailed in table , this

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TABLE . LIST OF PICASSO WORKS IN THE ANTIBES MUSEUM COLLECTION EXAMINED FOR THIS STUDY, ANALYTICAL TECHNIQUES USED, NUMBER OF SAMPLES AND POINTS OF

NON-INVASIVE ANALYSIS

Accessionnumber

Title Datea Media Support Dimensions(cm)

In situ Technique ofAnalysis (Numberof spots examined)

Samples (Techniqueof Analysis)

MPA.. Nature morte à labouteille, à la sole età l’aiguièreStill Life with Bottle,Sole and Ewer

Undated(September)

Oleoresinousenamel paint andcharcoal

Fibrocement × MIR (); NIR ();UV/VIS fluo () UV/VIS/NIR FORS ();XRF ()

new (FTIR)

MPA.. Satyre, faune etcentaure au tridentSatyr, Faun andCentaur with aTrident

Undated(October )

Oleoresinousenamel paint andcharcoal

Fibrocement × MIR (); NIR ();UV/VIS fluo () UV/VIS/NIR FORS ();XRF ()

None

MPA.. La Joie de VivreThe Joy of Life

Dated on verso

Oleoresinousenamel paint andcharcoal

Fibrocement × MIR ();UV/VISfluo () UV/VIS/NIR FORS ();XRF ()

historic (FTIR;FT-Raman; SEM/EDX on x-sections)

MPA.. La ChèvreThe Goat

Undated(November)b

Oleoresinousenamel paintwith charcoal

Plywood . ×.

MIR (); NIR ();UV/VIS fluo () UV/VIS/NIR FORS ();XRF ()

None

MPA.. Nu couché au litblancReclining Nude on aWhite Bed

Undated(November)b

Oleoresinousenamel paint

Fibrocement × MIR (); NIR ();UV/VIS fluo ()UV/VIS/NIR FORS(); XRF ()

None

MPA.. Nu couché au lit bleuReclining Woman ona Blue Bed

Dated on versoNovember ,

Oleoresinousenamel paint

Plywood × MIR (); NIR ();UV/VIS fluo () UV/VIS/NIR FORS ();XRF ()

None

MPA.. Nu assis sur fondvertSeated Nude onGreen Ground

Undated(November)b

Oleoresinousenamel paint

Plywood × . MIR (); NIR ();UV/VIS fluo () UV/VIS/NIR FORS ();XRF ()

historic (FTIR,PLM, SEM/EDX on x-section)

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MPA.. Nature morte aupanier, aux troisoursins, à la lampeStill Life withBasket, Three SeaUrchins and Lamp

Dated on versoOctober ,

Oleoresinousenamel paint andcharcoal

Reusedcanvas

. × . MIR (); UV/VISfluo () UV/VIS/NIR FORS ();XRF ()

new (FTIR,FT-Raman, SEM/EDX on x-sections)

MPA.. Nature morte auxvolets noirs aveccitron, murène,rougets, seiche ettrois oursinsStill Life with BlackShutters

Undated(October )

Oleoresinousenamel paint

Reusedcanvas

. × . MIR (); NIR ();UV/VIS fluo () UV/VIS/NIR FORS ();XRF ()

None

MPA.. Nature morte auxtrois poissons, à lamurène, au citronvert sur fond blancStill Life with ThreeFish, Moray Eel andLime on WhiteGround

Dated on versoSeptember ,

Oleoresinousenamel paint andcharcoal

Reusedcanvas

× MIR (); UV/VISfluo () UV/VIS/NIR FORS ();XRF ()

historic (FTIR,FT-Raman; SEM/EDX on x-section); new (FTIR,FT-Raman)

MPA.. Nature morte aucitron vert, aux deuxpoissons et à lamurène sur fond grisStill Life with Lime,Two Fish and MorayEel on Gray Ground

Dated on versoSeptember ,

Oleoresinousenamel paint andcharcoal

Reusedcanvas

× MIR (); UV/VISfluo () UV/VIS/NIR FORS ();XRF ()

None

MPA.. Nature morte auxpoissons noirsStill Life with BlackFish

Dated on versoOctober ,

Oleoresinousenamel paint

Plywood × . MIR (); NIR ();UV/VIS fluo () UV/VIS/NIR FORS ();XRF ()

historic (FTIR)

MPA.. Pêcheur assis à lacasquetteSeated Fishermanwith Cap

Dated on versoNovember ,

Oleoresinousenamel paint

Plywood . × . MIR (); UV/VISfluo () UV/VIS/NIR FORS ();XRF ()

new (FTIR)

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Accessionnumber

Title Datea Media Support Dimensions(cm)

In situ Technique ofAnalysis (Numberof spots examined)

Samples (Techniqueof Analysis)

MPA.. Faune jaune et bleujouant de la diauleYellow and BlueFaun Playing aDouble Flute

Dated on versoOctober ,

Oleoresinousenamel paint andcharcoal

Paper × . MIR (); UV/VISfluo () UV/VIS/NIR FORS ();XRF ()

None

MPA.. Faune blanc jouantde la diauleWhite Faun Playinga Double Flute

Undated(October ,)

Oleoresinousenamel paint

Paper . × MIR (); UV/VISfluo () UV/VIS/NIR FORS ();XRF ()

None

MPA.. Nature morte aucitron vert, aux deuxpoissons et aux deuxmurènesStill Life with Lime,Two Fish and TwoMoray Eels

Undated(September )

Oleoresinousenamel paint andcharcoal

Paper . × . MIR (); UV/VISfluo () UV/VIS/NIR FORS ();XRF ()

None

MPA.. Le Centaure et leNavireThe Centaur and theShip

Dated October, accordingto Zervos ()

Oleoresinousenamel paint andcharcoal

Papermounted oncanvas

× MIR (); UV/VISfluo () UV/VIS/NIR FORS ();XRF ()

None

aDates are listed in italics if the date is an estimate given by art historians.bEstimated dates for which scientific analysis may suggest a reconsideration.

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sub-set derived from a total of new samples takenfrom the edges of some of the paintings in , aswell as a group of approximately samples taken in from paintings in the collection, and preservedat the Centre de Recherche et de Restauration desMusées de France (CRMF), Paris (termed “historicalsamples” in the following). These samples were ana-lyzed with micro-Fourier Transform Infrared spec-troscopy (FTIR) occasionally complemented bymicro-Raman spectroscopy, Scanning ElectronMicroscopy with Energy Dispersive x-ray analysis(SEM-EDX), and polarized light microscopy (PLM).Technical details as well as a brief description of thecapabilities of each technique have been outlined in pre-vious publications (Miliani et al. , , ;Gautier et al. ) and are summarized in theAppendix.

. RESULTS AND DISCUSSION

.. ANALYSIS OF THE COLORED PAINTS

Analysis confirmed a fairly restricted palette for theworks painted by Picasso in Antibes. As described intable only nine types of colored paints—all oil-based—were identified on the surfaces of the works, in addition to several different types of blackpaint, four different types of white, and a gray colorobtained by mixing white paint with crushed carbon-based black. The crushed charcoal has been reportedto derive from used carbon rods of arc lamps that

were supplied to Picasso from the film studios in Nice(Tran ).The artist mostly used the paints straight out of the

can, with minimal mixing of different colors, as inferredby the very reproducible paint composition determinedwith the combination of non-invasive and micro-invasive techniques described in table . Additions ofvarying proportions of crushed carbon-based blacksto darken the colors, or white paint to lighten thetone (light yellow was used for the green colors) werethe main exceptions to this trend. For example, thetwo related works Still Life with Three Fish, MorayEel and Lime on White Ground (..), and StillLife with Lime, Two Fish and Moray Eel on GrayGround (..), painted on the same th day ofSeptember , illustrate Picasso’s limited manipu-lation of the ready-mix paints with simple additionsof white paint to lighten the tone. The paintings havea limited palette of white, light blue, gray, and darkgreen for the lime, with the light blue paint composedof Prussian blue (Fe[Fe(CN)]) with barium sulfate(BaSO) and zinc white (ZnO), as indicated by detec-tion of iron, zinc, and barium with XRF andconfirmed with micro-FTIR analysis of a samplederived from ... After baseline subtractionand XRF peak-fitting with the Bruker Artax proprie-tary software, ratios of peak areas of barium (Ba) Lαpeaks and iron (Fe) Kα peak show the same value ofBa/Fe = . for both paintings, which opens the possi-bility of the paint coming from the same can. Conver-sely, peak area ratios of zinc Kα and barium Lα peaks

FIG. . In situ analysis with fiber optics reflectance near infrared and mid-infrared spectroscopy (at left), as well as x-ray fluo-rescence spectroscopy (at right) in the galleries of the Musée Picasso, Antibes, France. A portion of the triptych Satyr, Faun andCentaur with Trident (..) by Pablo Picasso is visible.

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measured on areas of light blue paint are approximatelyhalf for .. than for .., which may indi-cate that a higher amount of zinc-based white wasadded to the lighter palette of ... Althoughthe XRF technique penetrates the paint layers downto the ground, because the two paintings have identicalgrounds of zinc white, kaolin, calcium carbonate,protein, and oil, as detected with micro-FTIR analysisof a historic sample, the variability of compositionrecorded with XRF must be related to the upperlayers of paint. Such hypothesis is confirmed by calcu-lating the first derivative of the reflectance spectrumof the light blue paint of .. and comparing itwith that obtained for ... The peak at nm, which is characteristic of zinc oxide paints (Bacciet al. ), is more intense for .. (fig. ).

Analysis of the maroon paint, which is present onseven of the examined works (two of which areshown in fig. ), demonstrated that the same ready-mixed enamel paint was likely used for the marooncolor of the various paintings examined (table ). Allthe Vis reflectance spectra collected on these paintsshow very similar curves with a reflectance minimumat nm and broader maximum at nm (fig. ).Some of the spectra perfectly overlap, while in generalonly an overall increase or decrease of reflectancevalues across all wavelengths was observed for thevarious artworks, reflecting the lighter or more satu-rated color appearance of each individual passage,due to the admixture of white, the variable thicknessof the paint layer or the influence of the different sup-ports (figs. , ). Not surprisingly, chemical analysis

TABLE . COLORS (AND RELATIVE PAINT COMPOSITION) CHARACTERIZED ON THE ANTIBES PAINTINGS BY PABLO PICASSODESCRIBED IN THIS STUDY

Color Pigments and Extenders Characterized Number of WorksIncorporating Color

Teal Prussian blue with significant amounts of barium sulfateextender and zinc white

Dark blue High amounts of Prussian blue with very little bariumsulfate and zinc white

Green I A little Prussian blue and finely dispersed chrome yellowwith barium sulfate, and likely also an organic green andzinc white

Green II Prussian blue with barium sulfate and yellow ocher withkaolinite clay

Yellow I Yellow ocher with kaolinite clay and zinc white

Yellow II A small amount of finely dispersed chrome yellow withbarium sulfate and zinc white

Maroon Red ocher with little burnt umber, zinc white, gypsum andquartz, kaolin and other clays

Reddish orange Red lead (lead tetroxide) with traces of lead white

Gray I Carbon black and zinc white with a small amount of ironbased blacka

Gray II White paint (of any type listed below) and crushed charcoal

Blacks Asphalt, iron based black, carbon blacks have all beendetected, either used together or individuallyb

White I Zinc white with minor amounts of barium sulfate

White II Zinc white with significant amounts of lithopone

White III Zinc white with no extendersc

White IV Zinc white with significant amounts of titanium whited

White preparation offibrocement panels

Calcite bound in very little oil medium, sometimes alsocontaining gypsume

aSimilar to Dark Gray Pearl (Gris Perle Foncé, #) of Ripolin.bSeveral additives including clays, quartz, calcium, and zinc compounds have been identified.cSimilar to Ripolin Snow white (Blanc de neige #).dFT-Raman analysis of a white sample from .. confirmed the presence of TiO in its anatase form.eThis is the preparation applied by Michel Sima.

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also confirms a high similarity in the composition of themaroon paints sharing visually similar colors. XRFanalysis of this color reveals iron with some calcium,manganese, and trace titanium, mixed with zinc whiteor other zinc-based compounds and lead-based driers.Presence of lead-based driers is inferred from the XRFspectra because of the low counts for the lead peaksand the fact that FTIR analysis of selected samplesdoes not identify the presence of lead white. Trans-mission FTIR analysis of a sample of maroon paintfrom Seated Fisherman with Cap (..) showssilicates, other clays, and iron oxide, which, alongwith the detection of iron and manganese with XRFseem to point to the presence of burnt or raw umberas pigmenting agent (fig. b). Although the use ofmanganese as a drier cannot be excluded, XRF analysisconsistently highlights higher levels of manganese in themaroon paints when compared to other paints, whichlikely indicate its use as pigmenting agent. Traces ofgypsum (CaSO•HO) and an oleoresinous binderwere also confirmed with FTIR along with the presenceof metal carboxylates characterized by a broad band at cm− and an envelope with a sharp feature at cm−.The ocher-colored paint present in Seated Fisherman

with Cap (..) (fig. b) and other two worksamong the ones described here also has a reproduciblecomposition. The elements detected with XRF are iron,manganese, calcium, strontium, titanium, and lead,which can be attributed to the presence of yellowocher pigment (FeO(OH) with clay), and lead driers,as also confirmed by transmission FTIR of a sample

of the ocher paint from this work, which identifies theclay associated with this ocher pigment as kaolinite(AlSiO(OH)) (fig. a). Trace titanium, manganese,and calcium compounds may be attributed to theclays associated with the natural yellow ocherpigment. Various levels of zinc white (ZnO)-basedpaints have also been detected in the yellow paints ofdifferent artworks, depending on the lightness of thehue. It is important to note here that the spectral fea-tures of kaolin are well evident in the NIR spectraand, although weak, still visible in the MIR spectra(fig. ). Because only the yellow ocher and maroonpaints used in Antibes contain kaolinite (table ) spec-tral features of kaolinite have therefore been used tomap the distribution of this yellow ocher pigmentacross the various works examined and to infer admix-tures with this yellow paint, especially in the greens(Green II).While non-invasive analysis has allowed an unprece-

dented level of materials characterization for thepainted surfaces enabling a thorough survey of theAntibes palette, in some cases the precise compositionof certain colors could not be unambiguously unraveledwithout micro-destructive sampling and further analy-sis. In particular, for the dark and muddy green paintpresent on Still Life with Lime, Two Fish and TwoMoray Eels (..), Still Life with Three Fish,Moray Eel and Lime on White Ground (..),Still Life with Lime, Two Fish and Moray Eel onGray Ground (..), and Seated Nude onGreen Ground (..), XRF analysis showed arather variable composition, with high levels of

FIG. . Reflectance spectra (and their first derivative, inset) acquired from the light blue paint of the Picasso paintings: (a).. and (b) .. showing different levels of zinc white mixed in the paint, characterized by the typical maximumof the first derivative centered around nm.

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barium, low levels of iron, traces of chromium, somelead, and zinc, which rendered interpretation compli-cated, and left doubts on the possible presence of ayet undetected organic yellow or organic greenpigment. MIR analysis of green areas in the SeatedNude on Green Ground (..) detected only

clear peaks for wax, a lipid binder, metal carboxylates,barium sulfate, and zinc oxalate, but discrete peaks forpigmenting substances were not detected. Similarly,NIR analysis only clearly distinguished signals for theoil-based binding medium. Transmission micro-FTIRanalysis of a historical sample of the green backgroundpaint of .. revealed an oleoresinous paint withmetal carboxylates and a very small amount of Prussianblue and barium sulfate, but still no evidence of ayellow pigment. Only after preparing a cross sectionof a the dark green background paint (fig. ) and per-forming micro-Raman spectroscopy on its surface, itwas possible to unambiguously identify chromeyellow (PbCrO), present only in few isolated pigmentgrains with generally minute particle size, and at suchlow levels to be below the detection limit of FTIR.

FIG. . Two of the works examined in this study showing asimilar maroon colored paint on their surfaces: (a) P. Picasso,The Centaur and the Ship, October , , oleoresinousenamel paint and charcoal on paper mounted on canvas(MPA ..; × cm) Musée Picasso, Antibes. © Ima-geArt, photo Claude Germain. © Estate of Pablo Picasso /Artists Rights Society (ARS), New York; (b) P. Picasso SeatedFisherman with Cap, November , , oleoresinous enamelpaint on plywood (MPA ..; . × . cm). PhotoE. Hubert, CICRP, Marseille, France © Estate of PabloPicasso / Artists Rights Society (ARS), New York.

FIG. . Fiber-optic reflectance spectra of the maroon paintin the – nm range for the paintings: (a) ..(green trace); (b) .. (black trace); (c) .. (lightgray trace); (d) .. (red trace); (e) .. (darkgray trace); and (f) .. (blue trace).

FIG. . Comparison of transmission FTIR spectra of micro-scopic samples of (a) reference Ripolin swatch of color BrunVan Dyck (#) (AIC B); and (b) a sample of maroonpaint from ... Although the two types of paints arevisually similar, their FTIR spectra show that the twomaterials do not contain the same components.

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Complementing the above-mentioned analysis,additional SEM-EDX analysis and PLM allowed thefull unravelling of the complex mixture composingthis paint. Taking into account the cumulative analyti-cal evidence described above, Green I is thus made ofzinc oxide, barium sulfate, carbon black, quartz,potassium-rich silicates, iron-rich clays with occasionallarge pyrite inclusions, calcium carbonate (CaCO),chrome yellow, some iron oxide, and traces of Prussianblue. Only very few and sporadic particles of Prussianblue are visible in the paint mixture, therefore part ofthe dark color must be explained also by the extensivepresence of carbon black. The large, splintery, inhomo-geneous particles of black material of extremely variedparticle size are clearly visible in the cross section andconfirm the artist’s admixture of crushed charcoal tohis paints (fig. ). The possibility that an unusualorganic green pigment might also be present (notcopper phthalocyanine though, which is to be excludedas a result of Raman and SEM-EDX analysis) is stillunder investigation. In fact, when dissolved in solventsthe paint produces an overall organic matrix of faintgreenish color without distinct green particles.As illustrated in table , the second type of green used

in all other works (Green II) is composed of Prussianblue with barium sulfate and yellow ocher with kaoli-nite clay. This color might well be a mixture of thecan of Prussian blue paint with paint of the Yellow Itype. This Green II is clearly distinguishable from

FIG. . Comparison of transmission FTIR spectra of (a) amicroscopic sample of yellow ocher paint from ..;and (b) a reference Ripolin Mat swatch of color Jaune Sable(#). These spectra seem to suggest that the two paints,while sharing similar hues, have different formulations,because of the different ratios of kaolinite clay with respectto the binding medium present in (a) versus (b). (c) MIR spec-trum of the ocher paint of .. taken at the painting’scenter, below the sailor’s hand: comparing this spectrumwith (a) it is evident that also the in situ measurement effec-tively highlights the presence of kaolinite, a lipid binder,and metal carboxylates in the Antibes paint.

FIG. . (a) Pablo Picasso, Seated Nude on Green Ground,oleoresinous enamel paint on plywood, (MPA ..; × cm) Photo E. Hubert, CICRP, Marseille, France© Estate of Pablo Picasso / Artists Rights Society(ARS), New York. Micrographs of a cross section from anhistorical sample of green paint in the background of thepainting illustrated in (a) imaged under: (b) visible light illumi-nation; (c) UV illumination; and (d) backscattered electron(BSE). The micrographs show the extreme complexity andvariable particle size of the mixture making up the greenpaint. Courtesy of CRMF, Paris, France.

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Green I described above based on the very recognizablefeatures of Prussian blue and kaolin in both the NIRand MIR spectra. Therefore, NIR and MIR non-invasive analysis allowed the precise mapping of thedistribution of the two main greens used in Antibesacross all the works tested, even though those tech-niques alone were not sufficient to allow unambiguousidentification of all the components in the two greens.

Overall both the non-invasive and micro-invasiveanalysis highlighted the presence of oil-based media,with transmission micro-FTIR spectroscopy sometimesuncovering also the presence of metal carboxylates andof a resinous component for the binders. The latter istypically indicated by a characteristic broadening ofthe carbonyl stretching for oils centered at cm−

toward lower wavenumbers, showing a more or lessprominent shoulder at cm−. In samples of theYellow I paint the FTIR spectrum shows bands forthe oil-based binding medium, as well as for metal car-boxylates (with a broad band centered at cm−

and a second broad but more structured band with asharp feature at cm−) (fig. ). FTIR spectra ofthe excised sample of maroon paint also show broaden-ing of the carbonyl stretching band at lower wavenum-bers, as well as the presence of broad features for metalcarboxylates (fig. b). Bands at , , , and cm− have been documented in aged paint repli-cas containing raw umber and sienna pigments in oiland have been attributed to manganese carboxylates(Mazzeo et al. ), additionally, zinc oleates havebands at , , , , , , and cm− (Robinet and Corbeil ). Such com-ponents might well be present in the highly convolutedbands visible in the spectra from the Picasso paintings: afull spectral deconvolution was not attempted.

. ANALYSIS OF THE WHITE PAINTS AND IMPLICATIONS FOR

DATING

Non-invasive XRF, MIR, NIR, UV/VIS fluorescence,and UV/Vis-NIR FORS techniques, used in conjunctionwith micro-FTIR and Raman spectroscopies whensamples were available, allowing the characterizationof four different types of white paints in the worksby Picasso described here. In addition to these a whitepreparation for the fibrocement panels based oncalcium carbonate bound in very little oil medium, insome cases containing gypsum, was also characterized.This was typically applied with regular brush strokes toeven out the porosity of the support and is left exposedin some of the works, such as, for example, ..and ... The four main types of white paintused for the works discussed in this paper contain anoleoresinous medium and zinc white (ZnO) in combi-nation with different other whites and extenders(table ). White I is composed of zinc white with

minor amounts of barium sulfate (BaSO). White IIcontains zinc white with significant amounts of litho-pone (ZnS co-precipitated with BaSO), the latterconfirmed by detection of zinc, barium, and sulfurwith XRF and by the typical peak of the first derivativeof the UV/VIS reflectance spectrum centered at nm(Bacci et al. ). White III has zinc white with noextenders, a composition matching that of Ripolinblanc de neige. White IV has zinc white with significantamounts of titanium white, identified as anatasewith micro-Raman spectroscopy in a sample fromStill Life with Basket, Three Sea Urchins and Lamp(..).

XRF spectroscopy was used systematically to analyzeall the works at numerous measurement points, includ-ing multiple measurements on different whites. Thisapproach allowed obtaining semi-quantitative infor-mation on the relative proportions of the variouselements present in single layers of white paints. Thefact that many works (especially those on wood paneland paper, but also a couple of those on fibrocement)were executed in single layers on mostly unprimed sub-strates is very advantageous for the analysis, as it mini-mizes interference from underlying layers of paint. XRFmeasurements were taken also on the substrates, whichare left exposed in some areas of most of the works,showing small elemental peaks of silicon, calcium,iron, and strontium derived from the components ofthe paper, fibrocement, and wood. These elements donot contribute or interfere with the levels measuredfor the major elements of interest: zinc, barium, andtitanium. After XRF baseline subtraction and peakfitting with the proprietary Bruker Artax software, netarea counts for peaks of the Kα of zinc, Lα of barium,and Kα of titanium were ratioed as appropriate.Because none of the paints contain titanium (TiO)and barium whites (BaSO) together, the overlap ofthe K and L lines for these elements is not of concernhere. In figure correlation plots for net area countsof titanium or barium versus zinc are shown and high-light satisfactory correlations, strengthening the quali-tative grouping of the white paints based on the typeof components detected on the surfaces. Specifically,values of R = . were calculated for White I (zincwhite with a little barium sulfate); R = . forWhite II (zinc white with lithopone), and R = .for White IV (zinc white with titanium white). Thewhite paint labeled White III contains zinc white only,without other whites or extenders, so no correlationplots were necessary or possible. The fact that insome cases the correlations deviate from ideality isdue to the nature of in situ measurements, where thegeometry of the instrument head with respect to thepainted surface is far from reproducible, and paintthicknesses as well as types of substrates vary signifi-cantly. Overall, though, the strong correlation

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reinforces the clear separation of the four different typesof white paint.After full characterization of the various formu-

lations, the synergistic and systematic use of XRF andUV/Vis-NIR FORS on all the paintings of the Antibescollection allowed the precise mapping of the distri-bution of the various white paints on the surfaces ofthe artworks. The survey reveals that most of the

works are painted only with one type of white paint,with notable exceptions. One is The Joy of Life(..), which likely contains several whitesbecause it was extensively reworked by Picasso fromSeptember, when he first started painting in the Gri-maldi castle, until his departure in November .The other two are Still Life with Three Fish, MorayEel and Lime on White Ground (..) and TheGoat (..). White II was identified in the fluidbrush strokes used to delineate the contours of theseated animal in The Goat (..) (fig. ),showing zinc white with significant amounts of litho-pone. Lithopone is clearly evident in the reflectancespectra recorded on this cool white paint (fig. ai),but it is absent from the broad brush strokes of thewarm white in the background, executed with a paintcomposed of zinc white with minor amounts ofbarium sulfate (White I) (fig. aii). The backgroundpaint only shows the UV/Vis-NIR FORS maximum at nm typical of zinc oxide, but lacks the maximumpeak of the derivative curve at nm characteristicof lithopone (Bacci et al. ), which is on the otherhand evident in figure b for the contour white.The use of four distinctive types of white paint

suggests some important considerations with regardto the date of execution of some of the works. It is tobe noted that Picasso only dated approximately halfof the works that have remained in the collections pre-served at the Grimaldi Castle. For the other paintings,

FIG. . Correlation plots of XRF data for white paintsfound on the entire corpus of the Picasso works investigatedin Antibes. The data points represent several measurementson several areas of the various artworks and the regressionlines demonstrate constant ratios of the main paint com-ponents across the three types of white paints that showzinc white combined with: (a) barium sulfate (White I); (b)l.c. lithopone (White II); and (c) titanium white (White IV).

FIG. . Pablo Picasso The Goat, , oleoresinous enamelpaint with charcoal on plywood, (MPA ..; . ×. cm): detail of the treatment of the neck area, with anarrow highlighting the presence of a second white paintused to accentuate the graphite lines. Photo E. Hubert,CICRP, Marseille, France

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such as, for example, Seated Nude on Green Ground(..), The Goat (..), and Reclining Nudeon a White Bed (..) (table ), the commonlyaccepted dates of execution relied on art-historical

suppositions based on other securely dated works thatwere considered stylistically close or on sketches con-sidered preparatory for the undated works (Giraudy–). The present characterization of the types ofwhites used by Picasso in Antibes, in combinationwith the firm chronology set by the dates inscribed bythe artist on some of the works, indicate that White Iwas used only in September, White II only inOctober, White III in two works dated September , (.. and ..) and then only inworks dated late October through November ,; White IV was used in works mostly datedbetween October , and October , (Casadio and Gautier ). Although it is not possibleto speculate on the artist’s intention for using suchdifferent whites based on scientific analysis alone, thescarce overlap of use of two or more whites in thesame painting, as well as the apparent linear temporalsuccession in Picasso‘s use of these whites seem tosuggest that simple material availability may haveguided this progression. This analysis, for example,ascertains that only four works in the entire Antibescycle contain the white paint with lithopone (White II,table ), and that this paint was no longer used forworks securely dated from mid-October through theend of Picasso’s stay in Antibes, in mid-November. These findings encourage a reconsideration ofthe supposed dates of execution for The Goat(..) and Reclining Nude on a White Bed(..), previously dated to November , andnow more likely considered to be painted in earlyOctober based on the presence of White II. Thematerials analysis is also strengthened by the obser-vation of historical photographs taken at the time ofPicasso’s work in the studio atop the Grimaldi castle(Sima et al. ), which show the two paintings inquestion at advanced stages of completion whileothers dated to later weeks in October are still inearly states (Casadio and Gautier ).

. COMPARISON WITH RIPOLIN PAINTS

In recent years, an extensive scientific investigation ofoleoresinous enamel paints produced by the RipolinCompany in France between and , has ledto a number of publications contributing to thereverse-engineering of the composition of these paints(Gautier et al. ; Muir et al. ). These publi-cations are based on the multi-technique analysis of areference set of approximately enamel paint cans,and Ripolin paint sample cards, each containingbetween and swatches of actual paint, dependingon the time of production and product line (Gautier). Previous analysis not only established thespecific composition of each of the colors sold by thecompany, but also ascertained that the composition of

FIG. . (a) Reflectance spectra of the white paints of TheGoat, (..) in the – nm range: (i) paintused for the outlines around the body; (ii) paint used for thewide and free-spirited brush strokes of the background. (b)First derivative of the reflectance spectrum illustrated inai, showing the presence of both lithopone and zinc whiteas evidenced by the maxima at and nm, respectively.

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such color hues remained fairly constant in the first halfof the th century, with minimal changes due to theintroduction of new pigments on the market (such asthe Hansa yellows, for example, which were introducedas substitutes for some yellows based on chromates)(Gautier et al. ). Such an extensive collection rep-resents a benchmark to which unknown compositionscan be compared, to ascertain similarity with Ripolincompositions. The specificity of the composition ofsome of the enamel paints encountered in this studyof the Antibes collection, together with limited analysisof other types of contemporary enamel paints of thebrands Valentine and Triton (Casadio and Gautier), which also show specific but markedly differentcomposition, demonstrates that a match with knownRipolin paint compositions might offer sufficientproof to ascribe the unknown paints to the famousFrench brand.The availability of extensive recent knowledge of

Ripolin paints indicates that for the works describedhere, only very few paints matched known compo-sitions of Ripolin enamels (Gautier ; Muir et al.) (table ), contrary to previously publishedresults (Giraudy –). A few examples aredescribed in the following, whereas positive matchesfor all the works examined for this study are reportedin table .The maroons of Antibes have a very similar hue to

the Ripolin color Van Dyck brown (Brun Van Dyck,#). However, the FTIR signatures for gypsum andclay are not visible in the spectrum of the Ripolinpaint, while they are very evident in a sample ofmaroon paint from .. (fig. ). Ripolin’s VanDyck brown is mainly composed of iron oxide(FeO) in a drying oil medium rich in natural resin,as evidenced in the FTIR spectra by a broad carbonylstretching band showing contributions from a lipidiccarbonyl, centered at approximately cm−, andthe resin carbonyl stretching, centered at cm−.Because all the Antibes maroon paints show a similarcomposition, but they are different from the compo-sition of several known examples of historic RipolinVan Dyck brown paints, it can be concluded that allmaroon-colored paints of Antibes came from thesame manufacturer, but they were not painted withRipolin paint.The areas painted with Yellow I visually match the

Sand Yellow (Jaune Sable) hue available in theRipolin Mat paint line. The latter is actually the onlyocher-colored paint in the Ripolin range to notcontain chrome yellow, which is absent from theAntibes paint Yellow I. However, transmission FTIRspectra of Ripolin Mat Jaune Sable (#) paints com-pared with a microscopic sample of yellow ocher paintfrom the Antibes painting .. show differentrelative intensities for the band at cm− due to

OH stretching in kaolinite, and those of the carbonylstretching of the medium, centered at cm−

(fig. ). The different proportions of binder/kaoliniteseem to suggest a different kind of yellow ocher paintused in Antibes other than Ripolin.One of the Antibes paints that matches historical

Ripolin formulations is Gray I, composed of carbonblack and zinc white with a small amount of iron-basedblack. This composition matches that of Ripolin GrisPerle Foncé #. This paint is found on several worksincluding .., .., and ...Finally, as discussed in the earlier section, the white

paint labeled White III matches the composition ofRipolin Blanc de Neige #, when comparing XRF,MIR, and micro-FTIR results. This white paint isfound on .., .., .., ..,.., and ...

. DETERIORATION PRODUCTS AND SURFACE COATINGS

As illustrated in table , the presence of carboxylatesof zinc and other metals has been detected in most of theworks, with broad FTIR bands centered at and cm−, and MIR features showing an inverted rest-strahlen effect peak centered at cm−. These metalcarboxylates are likely either derived from interactionof the zinc-rich paint with the oleoresinous binder, orintroduced as organometallic complexes used to cata-lyze the curing process of the enamel paints. In somecases, infrared analysis with MIR and transmissionFTIR when samples were available highlighted the pres-ence of specific bands for zinc oxalates, with a broadpeak at cm− and a sharp doublet at and cm−. Calcium oxalates have also been detectedin correspondence of the exposed white preparationof some of the fibrocement panels, showing a sharpband at cm−. For example, in the triptychSatyr, Faun and Centaur with Trident (..)MIR spectra of the exposed support with the mattechalk-based preparation applied by Sima show peaksat and cm− that are typical for calcium car-bonate, an inverted band centered at cm−

attributable to gypsum and the sharp peak of calciumoxalates centered at cm− (fig. a). On theother hand, MIR analysis of the glossy white paintused to erase a previous composition on the same trip-tych shows the combination bands of CH stretchingtypical of lipidic binders centered at and cm−, the sharp bands at and cm− attribu-ted to zinc oxalate, the broad inverted band of metalcarboxylates centered at cm− and the character-istic combination band at cm− of bariumsulfate (Miliani et al. ). Because of the presenceon the same work of oxalates of zinc and calcium, itcan be reasonably hypothesized that the compoundsdetected on the paintings are products of reaction of

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TABLE . SUMMARY OF PAINT MATERIALS, SURFACE COATINGS AND DEGRADATION PRODUCTS DETECTED ON THE ANTIBES PAINTINGS DESCRIBED IN THIS PAPER, WITH

INDICATIONS OF LIKELY USE OF RIPOLIN PAINTS

AccessionNumber

Pigment Palettea WhitePaint

BindingMedia

SurfaceCoatings

Oxalatesb Other MetalCarboxylates

Match with RipolinComposition

MPA.. Gray I and II White I Drying oiland resin

None Y Y Gray I matches with RipolinGris Perle Foncé #

MPA.. Charcoal lines White II Drying oiland resin

None Y Y None

MPA.. Yellow II; Teal; Green II; Maroon;Reddish- orange; Black

White II,III, IV

Drying oiland resin

Wax Y Only in someareas

White III matches with RipolinBlanc de Neige #

MPA.. Charcoal lines White I,II

Drying oiland resin

None Y Only in someareas

None

MPA.. Green II; Maroon; Teal White II Drying oiland resin

Wax Y Y None

MPA.. Gray I; Dark blue WhiteIII

Drying oiland resin

None Y Y Gray I matches with RipolinGris Perle Foncé #; White IIImatches with Ripolin Blanc deNeige #

MPA.. Green I; Gray I: Black White I Drying oiland resin

Wax/acrylic

Y Y Gray I matches with RipolinGris Perle Foncé #

MPA.. Maroon; Yellow I; Green (Prussianblue with chrome yellow); Teal;Black

WhiteIV

Drying oiland resin

Acrylic (Y) Y (only in onespot)

None

MPA.. Maroon; Green II; Teal; Black;Reddish- orange

WhiteIV

Drying oiland resin

Acrylic Y Y None

MPA.. Green I; Teal White I/III

Drying oiland resin

Wax (Y) Y White III matches with RipolinBlanc de Neige #

MPA.. Green I; Teal, Gray II WhiteIII

Drying oiland resin

None (Y) N White III matches with RipolinBlanc de Neige #

MPA.. Yellow I; Light greenish- yellow(yellow ocher with kaolinite clay,crushed charcoal, trace Prussianblue and zinc white); black

WhiteIII

Drying oiland resin

Syntheticcoating

N Y White III matches with RipolinBlanc de Neige #

MPA.. Teal; Maroon; Yellow I; Black WhiteIII

Drying oiland resin

None Y Y White III matches with RipolinBlanc de Neige #

MPA.. Teal, Yellow II; Maroon WhiteIV

Drying oiland resin

None (Y) N None

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the paints with the marine atmosphere. Since the museumdirectly overlooks the water, these paintings have a par-ticularly high exposure to the marine air, which is notor-iously rich in oxalic and other dicarboxylic acids (KalyaniMartinelango et al. ). Although another possibleroute of formation of zinc oxalates is linked to theaction of microorganisms, no evidence of biodeteriora-tion was observed on the examined works (Cariatiet al. ; Rampazzi et al. ). Zinc oxalates havebeen highlighted recently in works of Piet Mondrian(Miliani et al. ) and Edvard Munch (Frøysakeret al. ) among others. The potential conservationimplications of the presence of such compounds oneasel paintings have yet to be fully investigated.Although most of the paintings do not show a surface

varnish, a few isolated instances of acrylic coatingswere highlighted. These were not noted in the objectfiles at the Museum, which in general have veryscarce conservation documentation. MIR analysis ofall seven areas probed on Still Life with Basket, ThreeSea Urchins and Lamp (..), indicated the pres-ence of an acrylic compound. In this case, a samplewas available for micro-invasive analysis with trans-mission micro-FTIR spectroscopy, which clearly ident-ified a pEA-MMA copolymer (fig. ). MIR analysis ofStill Life with Black Shutters (..) also detectedthe presence of an acrylic coating in four of the six spotstested, and although the spectral features were not suffi-cient to determine its nature unambiguously, its pres-ence would have gone undetected given that a samplefrom that painting was not available.M

PA..

(Onlywhite

paintused)

White

IVDryingoil

andresin

Non

e(Y

)N

Non

e

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..

GrayII;T

eal,Green

IWhite

IDryingoil

andresin

Non

eN

NNon

e

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..

Yellow

II;G

reen

II;M

aroo

n;Teal;

Black

White

IIDryingoil

andresin

Non

eN

YNon

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entsan

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bIfno

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sarein

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thesign

alforox

alates

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rather

weak.

Y=yes;N

=no

.

FIG. . MIR spectra of white paints in P. Picasso Satyr,Faun and Centaur with Trident (..) measured on: (a)evenly applied layer of calcium based preparation of the fibro-cement support showing calcium carbonate, gypsum, andoxalate; and (b) a line of glossy paint used to erase a previouscomposition, fluorescing white under UV illumination,showing lipid, zinc oxalate, metal carboxylates, andbarium-sulfate.

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Interestingly, extensive or partial coatings of waxhave also been identified, which could represent anoriginal artist’s intervention or another undocumentedtreatment, such as, for example, a consolidation effort.In particular, wax has been detected in the green andblack areas tested in Seated Nude on Green Ground(.) and in the green, maroon, and light blue—but not white—paints in Reclining Nude on a WhiteBed (..). The wax coating is most pervasive inThe Joy of Life (..), where it was detected inall colors tested across the entire expanse of thepainting.

. CONCLUSIONS

Through a combination of non-invasive and micro-invasive analytical techniques the palette of Picassofor an important corpus of paintings and works onpaper in the Antibes collection has been scientificallyand thoroughly characterized, dispelling longstandingambiguities that ascribed all the paints to the Frenchfirm Ripolin, including speculations that some may bealkyds. This work demonstrates that of the artworksand types of colors described here, only one whiteand one gray paint have compositions matchingRipolin paints, used in combination with other typesof ready-mixed, commercial oleoresinous enamelpaints.

Combined elemental, electronic, and molecular spec-troscopies were crucial in recognizing and clearly cate-gorizing for the first time the use of several types ofwhite paints. While all contain oleoresinous binders,

compositional differences involving the use of zincwhite alone or in combination with titanium white,barium sulfate, and lithopone were highlighted. Ulti-mately, the classification of the different white paintsused in concert with historical photographs by MichelSima documenting Picasso’s work in progress andother art historical information, has allowed a material-based refinement of the chronology and dating of someof the undated works.

Non-invasive infrared (MIR and NIR) analysis wasalso crucial in proving that, despite their date, the paint-ings in Antibes do not contain alkyd paints. The abilityto probe several points on all the paintings analyzedresolved any doubts on the completeness of thesurvey. Additionally, the presence of surface coatingscomposed of wax and acrylic resins have been high-lighted. These possibly document the artist’s interven-tion (in the case of wax) and surely indicateundocumented restoration interventions (the acrylics).Last, but not least, the pervasive presence of zinc andcalcium oxalates and other metal carboxylates hasbeen highlighted here for the first time. The detectionof oxalates on easel paintings, and especially onmodern paintings, is still rather rare, but a growingnumber of cases have recently been observed andshould be documented. These discoveries will undoubt-edly have relevance for future conservation campaignsand will provide helpful indications about the bestapproaches to the long-term preservation of these out-standing works.

Ultimately, this newfound information sheds light onthe relationships among the works in the collection andilluminates Picasso’s working materials and process inAntibes. Synergistic and interdisciplinary collabor-ations between scientists and those in charge of collec-tions are of vital importance to ensure that the greatamount of data unearthed through scientific analysiscan be correctly interpreted within the historicalcontext of the works, and hence might potentiallyaffect scholarship, the writing of Museum labels, andthe conservation of the collection.

ACKNOWLEDGMENTS

At the Art Institute of Chicago (AIC), the authors thank FrankZuccari, Stephanie D’Alessandro, Douglas Druick, JackBrown, and the staff of the Ryerson & Burnham Libraries.Special thanks go to Inge Fielder for her detailed SEM-EDXand PLM analysis of the green paint from ...Marilyn McCully and Michael Raeburn are also thanked,as well as Laure Nectoux and colleagues from the PPGgroup (Moreuil, France, current owners of Ripolin). The A.W. Mellon Foundation, the Barker Welfare Foundation, theGrainger Foundation and the Community Associates of theArt Institute of Chicago support scientific research and scien-tific instrumentation at AIC and are gratefully acknowledged.The Stockman Family Foundation is thanked for its support

FIG. . Comparison of FTIR spectra of paints from StillLife with Basket, Three Sea Urchins and Lamp (..):(a) in-situ MIR spectrum in an area of light blue paint, high-lighting the presence of Prussian blue, lipid binder, an acryliccoating, and barium sulfate; and (b) transmission micro-FTIRspectrum of a surface coating peeled off a sample of blackpaint, closely matching with a pEA-MMA acrylic copolymer.

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of the Ripolin project at AIC. SEM-EDXwork was performedat the EPIC facility of NUANCE Center at Northwestern Uni-versity. NUANCE Center is supported by NSF-NSEC,NSF-MRSEC, Keck Foundation, the State of Illinois, andNorthwestern University. Molab’s equipment and expertisewere made available through the transnational accessservice offered with support of the European Communitythrough the th FP (CHARISMA project n. ). GillesBarabant, Béatrice Sarrazin, Nathalie Balcar, and colleaguesat the Centre de Recherche et de Restauration des Muséesde France (CRMF), Paris, facilitated access to the historicalsamples and archival technical information on the Antibessamples. Roland May, Alain Colombini, Emilie Hubert, andcolleagues at the Centre Interdisciplinaire de Conservationet Restauration du Patrimoine (CICRP, Marseille) arethanked for their contributions, as well as the staff at theMusée Picasso, particularly Isabelle Le Druillennec and allthe technical personnel for their invaluable practical assist-ance. Benoît Dagron, conservation advisor for the MPA col-lection, is gratefully acknowledged for sharing his helpfulinsights.

APPENDIX

. XRF ANALYSIS

Analysis was performed non-invasively and in situ with aBruker TRACeR III-V energy dispersive x-ray fluorescenceanalyzer. The hand-held system has a rhodium target. The res-olutionof the system is approximately eV for the fullwidthat half maximum of the Mn Kα line. Several measurementswere taken at various locations to ensure accuracy and repro-ducibility of the results. The aperture of the instrument emits anx-ray beam of approximate spot size mm. The acquisitionparameters used for this investigation were kV and. µA with collection times of s (live time).

. MOLAB MOLECULAR AND ELECTRONIC

SPECTROSCOPY EQUIPMENT

Fiber-optic Fourier transform mid-infrared spectroscopy(MIR)—Spectra were acquired using a portable JASCO VIR spectrophotometer equipped with a Remspec mid-infrared fiber-optic sampling probe. The probe is made ofchalcogenide glass that allows the collection of spectra inthe range of – cm− at a resolution of cm−. Eighthundred scans were collected at each location. The width ofthe investigated area, determined by the probe diameter, isca. mm.

Fiber-optic Fourier transform near-infrared spectroscopy(NIR)—Near-infrared spectra were recorded with a portableJASCO VIR spectrophotometer. The spectral range is,– cm− with a resolution of cm−. Twohundred to scans were collected at each location. Thespectrophotometer is equipped with a silica glass fiber-opticY sampling probe that has a spatial resolution of about mm.

Fiber-optic UV/visible—near-infrared reflectance spec-troscopy (UV/Vis-NIR FORS)—UV–vis reflectance spectrawere collected by a portable probe in the range of

– nm at -nm resolution. The probe is placedapproximately mm from the measured surface.

UV–Vis fluorescence spectroscopy—A homemade portablefluorimeter was used. It utilizes a -W Xenon lamp as exci-tation source (λexc = nm), a H- Jobin Yvon UV mono-chromator for selecting the excitation wavelength, afiber-optic system to direct the excitation light on the sampleand convey the emitted light to an Avantes CCD spectrometer.Data are collected between and nm with a spectralresolution of nm and spatial resolution of mm.

. MICRO-INVASIVE ANALYTICAL TECHNIQUES

Micro-FTIR spectroscopy—A Bruker tensor FTIR spec-trophotometer with mid-IR glowbar source was used,coupled to a Hyperion Automated FTIR microscopewith nitrogen-cooled mid-band and broad-band MCTdetectors (covering the range ,– and ,–cm−, respectively). Samples were analyzed in transmissionthrough the microscope after compression in a diamondmicrocompression cell, at a resolution of cm−.

Micro-Raman spectroscopy—A Labram confocalRaman microscope (HORIBA Jobin Yvon, Edison, NJ,USA) was used, equipped with an Andor multichannelPeltier-cooled open electrode charge-coupled device detector,holographic notch filter, and two dispersive gratings ( and, grooves/mm). The excitation line of a solid-state diodelaser (λ = . nm) was focused through a × objectiveonto the samples and Raman scattering was back-collectedthrough the same microscope objective. Power at thesamples was kept very low (on average µW) by a seriesof neutral density filters in order to avoid any thermaldamage.

Scanning electron microscopy-energy dispersive x-ray spec-troscopy—A variable-pressure SEM (Hitachi, San Francisco,CA, USA, S-N-II) was used, coupled with Oxfordenergy dispersive x-ray spectroscopy and Hitachi solid statebackscattered electron detector, housed at The ElectronProbe Instrumentation Center (EPIC), part of the Northwes-tern University Atomic and Nanoscale Characterization(NUANCE) Center.

Cross-section preparation and optical microscopy—Micro-scopic paint samples were mounted in Bio-Plastic polyesterresin and ground and polished on silicon carbide grit papersand Micromesh cloths. The sections were examined with aZeiss Axioplan Research Microscope equipped withreflected light/UV fluorescence and documented with a ZeissAxioCam MRc digital camera.

Polarized light microscopy—Pigment samples wereremoved with a scalpel and mounted in Aroclor mount-ing medium (refractive index: .). The pigments were ana-lyzed using a Zeiss Universal Research Microscope usingtransmitted light in bright field and crossed polarizationwith a magnification range of –,×.

NOTE

. Various terms are used in the literature to identify non-artists’ paints: house paint, boat paints, enamel paints,gloss paints, industrial paints, commercial paints, ready-made or ready-mix paints etc. (Standeven ). To

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avoid confusion, in this paper the term oleoresinousenamel paint is used to refer to these ready-mixed,over-the-counter paints independent of their intendedend use, but preserving a distinction from alkyd-basedenamels.

REFERENCES

Andral, J. L. .Musée Picasso Antibes: A guide to the col-lections. Paris: Hazan.

Bacci, M., M. Picollo, G. Trumpy, M. Tsukada, andD. Kunzelman. . Non-invasive identification ofwhite pigments on th-century oil paintings by usingfiber optic reflectance spectroscopy. Journal of theAmerican Institute for Conservation : –.

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AUTHOR BIOGRAPHIES

FRANCESCA CASADIO is an A.W. Mellon senior conservation scientist at the Art Institute of Chicago where in she establishedand directs the conservation science laboratory. She also founded and co-directs the Northwestern University/ Art Institute ofChicago Center for Scientific Studies in the Arts (NU-ACCESS). She received her Ph.D. and M.S. degrees in Chemistry fromthe University of Milan, Italy. Address: The Art Institute of Chicago, Conservation Department, S. Michigan Ave.,Chicago, IL, , USA. Email: fcasadio@artic.edu.

COSTANZA MILIANI earned a Chemistry degree at the University of Perugia in and received a Ph.D. in Chemistry in .Currently, she is a researcher at the CNR-ISTM (Istituto di Scienze e Tecnologie Molecolari) in Perugia. Her scientific interestsare mainly focused on the development and application of non-invasive spectroscopies for the study of artwork. She has authoredover articles concerning structural, electronic, and vibrational properties of materials of interest for cultural heritage. Address:

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Istituto CNR di Scienze e Tecnologie Molecolari (ISTM-CNR), c/o Dipartimento di Chimica, Via Elce di sotto, , Perugia IT-. Email: miliani@thch.unipg.it.

FRANCESCA ROSI is Researcher in the Chemistry Department of the University of Perugia. Her research interests include the appli-cation and development of non-invasive and portable spectroscopic techniques for studying materials of interest in the field ofcultural heritage. Address: Centro SMAArt, c/o Dipartimento di Chimica, Via Elce di sotto, , Perugia IT-. Email:franci@thch.unipg.it.

ALDO ROMANI earned a Chemistry degree at the University of Perugia in and received his Ph.D. in Chemistry in . Cur-rently, he is a researcher at the Chemistry Department of the University of Perugia. He has authored about scientific papersconcerning both basic and applied subjects principally involving characterization of the excited states of organic molecules bymeans of the parameters that govern their radiative and nonradiative processes using spectroscopic techniques in absorptionand emission. These techniques have been also applied, for nondestructive diagnostic purposes, in the field of the cultural heri-tage. Address: As for Rosi. Email: romani@unipg.it.

CHIARA ANSELMI received her Chemistry degree at the University of Pisa in with Prof. F. Bellina, and her Ph.D. at theLudwigs-Albert Universität of Freiburg i. B. (Germany) working with professor R. Brückner. She joined the Center of ExcellenceSMAArt (ScientificMethodologies applied to Archaeology and Art) group at the University of Perugia in , dealing with non-invasive analysis methodologies for cultural heritage material. After a fellowship at EPFL in Lausanne with professorM. Grätzel, she now develops and tests materials for Dye-Sensitized Solar Cells (DSSC). Address: As for Rosi. Email:chiaraans@inwind.it.

BRUNETTO GIOVANNI BRUNETTI is Professor of General Chemistry at the University of Perugia. Author of scientific publicationson chemical reaction dynamics and spectroscopy applied to cultural heritage, he served as coordinator of the FP EU co-fundedproject EU-ARTECH. Currently coordinates CHARISMA, a co-funded EU project within the Programme “Capacities.” Address:As for Rosi. Email: bruno@dyn.unipg.it.

ANTONIO SGAMELLOTTI is Professor of Inorganic Chemistry at the University of Perugia, President of the Center of ExcellenceSMAArt (Scientific Methodologies applied to Archaeology and Art), and author of more than scientific publications onadvanced computational chemistry and on spectroscopic investigations of artwork materials. Address: As for Rosi. Email:sgam@thch.unipg.it.

JEAN-LOUIS ANDRAL has a graduate degree in Musicology and a Master in Archeology and History of Art from the University ofStrasbourg, France. From to , he was Curator at the Musée d’art moderne de la Ville de Paris. Since , he has beenthe Director of the PicassoMuseum, Antibes. Address: Musée Picasso, Antibes, France. Email: jean-louis.andral@ville-antibes.fr.

GWÉNAËLLE GAUTIER holds a Ph.D. in Chemical Sciences from the University of Pisa (Italy, ). She was a Post Graduate fellowin the Chemical Science for the Safeguard of the Cultural Heritage Group at the University of Pisa in . From to ,she worked at the Art institute of Chicago in various positions culminating in the role of AndrewW.Mellon Associate Conserva-tion Scientist. Email: gwenclaire@gmail.com.

Résumé – Le Musée Picasso à Antibes (France) possède une collection unique de peintures et œuvres surpapier par Pablo Picasso, réalisées durant l’automne par l’artiste, travaillant dans les mêmes bâtiments quele musée occupe aujourd’hui. Picasso a peint avec des matériaux facilement disponibles dont des peintures émailoléorésineuses, du fibro-ciment, des panneaux de bois, des feuilles de papier et des toiles réutilisées. Cet articledécrit les résultats d’une campagne complète d’analyses scientifiques de de ces œuvres avec à la fois des tech-niques non invasives et micro-invasives. Le projet a élucidé la palette intégrale des peintures, dissipant le mythede leur exécution exclusivement avec la marque renommée de peinture émail Ripolin. L’utilisation combinée etefficace de méthodes d’analyses élémentaires et spectroscopiques a permis des distinctions précises entre différentstypes de peintures émail blanches utilisées par Picasso à Antibes. L’artiste ayant vraisemblablement utilisé de tellespeintures suivant un ordre chronologique, l’identification précise du type de peinture blanche utilisée sur chacunedes œuvres permet l’attribution de dates sur des œuvres jusqu’alors non datées. De nouvelles informations impor-tantes ont aussi été mises à jour relativement aux finitions des surfaces à base de cire et de vernis polymères mod-ernes, ainsi qu’à la présence courante de savons métalliques, dont des oxalates de zinc.

Resumen – El Museo Picasso en Antibes (Francia) alberga una singular colección de pinturas y obras sobrepapel de Pablo Picasso, terminadas por el artista durante el otoño de , quien trabajaba en el mismo sitio quehoy ocupa el Museo. Picasso pintaba con los materiales fácilmente disponibles incluyendo pinturas oleo resinosas al

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esmalte, fibrocemento, paneles de madera, hojas de papel y lienzos vueltos a usar. En este trabajo se describen losresultados de una extensa campaña de análisis científicos de de estas obras, hechos con técnicas no invasivas ymicro-invasivas. El proyecto esclarece la paleta completa de las obras, desvanece los mitos a cerca de su realizaciónllevada a cabo únicamente con la pintura al esmalte muy popular, Ripolin. La combinación efectiva de métodos deanálisis elementales y espectroscópicos hizo posible la discriminación muy detallada entre varios tipos de pinturablanca utilizada por Picasso en Antibes. Ya que parece que el artista utilizó estas pinturas en secuencia cronológica,la identificación exacta del tipo de pintura blanca presente en cada una de las obras permitió que se asignaran fechasa algunas de las obras que no tenían fecha. También se descubrió nueva información importante sobre recubrimien-tos de cera y barnices poliméricos modernos, tanto como la presencia generalizada de jabones metálicos incluyendooxalatos de zinc.

Resumo –OMuseu Picasso emAntibes (França) abriga uma coleção rara de pinturas e obras de arte em papelde Pablo Picasso, feitas pelo artista durante o outono de , enquanto trabalhava no mesmo local hoje ocupadopelo Museu. Picasso pintou com materiais facilmente disponíveis, inclusive tintas esmaltadas óleo-resinosas, fibro-cimento, painéis de madeira, folhas de papel e lonas reaproveitadas. Nesta pesquisa são descritos os resultados deampla atividade de análise científica realizada em dessas obras, tanto com técnicas não invasivas quanto commicro invasivas. O projeto elucidou a paleta completa das pinturas, desfazendo mitos sobre sua realização exclu-sivamente com a renomada marca de tinta esmalte Ripolin. A combinação efetiva de métodos de análise elementar eespectroscópica possibilitou distinções precisas entre vários tipos de tinta esmalte branca usadas por Picasso emAntibes. Uma vez que o artista parece ter usado tais tintas em sequência cronológica, a identificação exata dotipo de tinta branca presente em cada obra possibilitou a datação de algumas das pinturas não datadas.Também foi revelada informação nova e importante sobre os revestimentos de cera e de modernos vernizes polimér-icos, bem como sobre a ampla presença de sabões de metais, inclusive oxalatos de zinco.

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