TRACES OF ANCIENT COLOURS ON TRAJAN'S COLUMN*

Recent restorations of Trajan's Column uncovered two marble fragments bearing traces of pigments, bright red (minium, hematite) in one case, and yellowish-orange (minium, hematite, clay minerals) in the other. Both were applied to the marble surface on a plaster underlayer. The presence of an underlayer and of surfaces coloured according to subject tells us that the colours were applied deliberately. Although the use of minium plus hematite is confirmed by archaeological finds, there is only a good probability that the colours were applied on the column at the time of its completion.     

Composition of the Lustre Pigment Used in the Production Of 13th Century AD Raqqa Lustreware from Syria

The very rare find of the relic of the original lustre pigment attached to the glazed surface of a sherd of 13th century ad Raqqa type lustreware from Syria has been analysed using a combination of analytical scanning electron microscopy (SEM), micro‐X‐ray diffraction (XRD) and Rutherford backscattering spectroscopy (RBS). The composition of the pigment relic inferred from these analyses is shown to match those of recipes for lustre production given in the early treatises by Jazbir Ibn Hayyan (c. ad 721–c. ad 815) and Abū'l Qasim (ad 1301). Similarities and differences between this 13th century ad Syrian pigment and pigments used in the ninth century ad in Iraq, in the 14th century ad in Islamic and Hispano‐Moresque Spain, and in the 16th century ad in Renaissance Italy are discussed.     

Bitumen in Early Ceramic Art: Bitumen‐Painted Ceramics From Late Neolithic Tell Sabi Abyad (Syria)*

The paper presents the results of a chemical analysis of black pigment used to decorate pottery from Late Neolithic Tell Sabi Abyad, northern Syria (c. 6100 cal bc ). The pigment appears to be bitumen. A comparison with known reference samples from modern locations of bituminous sources in the Near East suggests that the bitumen used to paint ceramics at Tell Sabi Abyad came from at least two different source areas in northern Iraq. The bitumen‐painted ceramics at Tell Sabi Abyad represent the earliest evidence attested so far of bitumen used as a pigment for pottery decoration.     

The Production of Lead–Tin Yellow at Merovingian Schleitheim (Switzerland)*

A Merovingian crucible fragment, with internally adhering yellow glass, and yellow glass beads of the same region and period were investigated by non‐destructive XRF, optical microscopy and SEM‐EDS. Although the microstructure and chemical composition of the yellow pigment (lead–tin yellow type II, ‘PbSnO₃’) are almost identical in both the beads and the crucible, in the latter the pigment occurs in a much higher concentration. However, the glass base in the beads and the crucible is very different, indicating that the beads were not manufactured directly from the crucible. Instead, the crucible most likely served to produce lead–tin yellow, which was subsequently mixed elsewhere with a colourless soda–lime glass to produce yellow glass beads.     

RESEARCH ON THE PIGMENTS FROM PAINTED CERAMICS EXCAVATED FROM THE YANGQIAOPAN TOMBS OF THE LATE HAN DYNASTY (48 BC – AD 25)

The analysis of pigments on painted ceramics excavated from the Yangqiaopan Tombs of the late Western Han Dynasty was undertaken using optical microscopy (OM), micro‐Raman spectroscopy (μ‐RS), scanning electron microscopy with energy‐dispersive X‐ray spectrometry (SEM–EDS), X‐ray diffraction (XRD) and Fourier‐transform infrared spectroscopy spectra (FTIR). The pigments were identified as red lead (Pb₃O₄), carbon (C), malachite [Cu₂CO₃(OH)₂], Chinese purple (BaCuSi₂O₆) and illite {[K,H₃O]Al₂Si₃AlO₁₀(OH)₂}. Fibrous materials were observed in some pigment samples. When observed by SEM, one showed a large amount of fibre in solidified gum, which indicated that gum of ramie could have been used as the binding medium to make the pigment particles adhere together. These results provide significant insights into the characteristics of these pigments in the Qin and Han Dynasties.     

STUDY ON THE PIGMENTS IN THE CRUCIFORM GALLERY OF ANGKOR WAT,CAMBODIA

In the cruciform gallery of Angkor Wat in Cambodia, red, orange, white and black pigments were widely painted on the surfaces of pillars, walls and friezes. The application sequence of the pigments is different from area to area. The following substances were confirmed from the pigments: hematite (laterite), minium, calcium oxalate hydrates (whewellite and weddellite), Pb–Cl compounds (cotunnite, laurionite and blixite), calcium phosphates (whitlockite), gypsum, hydrocerussite, calcite, anglesite, lead dioxide, azurite and carbon black. The orange pigment (minium) underlies the red pigment (hematite). The former may have been applied at the time of the foundation (the Angkor Wat style period), and the latter in the Bayon style period or later, but mainly before the early 17th century of the current era.     

IDENTIFICATION,PROCESSING AND USE OF RED PIGMENTS (HEMATITE AND CINNABAR) IN THE VALENCIAN EARLY NEOLITHIC (SPAIN)

The results of the first elemental and structural physicochemical analyses (SEM–EDX, TXRF, XRD, FTIR, GC and EDXRF) of Early Neolithic red pigment samples from the region of Valencia confirm one of the earliest uses of cinnabar (HgS) in Spain (5300 to 5000 cal bc ). They also inform on the storage of massive quantities of hematite and the development of specific technologies of hematite‐based paint production and use. The samples were recovered at the three most significant Early Neolithic sites of the Mediterranean coast of Spain: Cova de l'Or (Beniarrés, Alacant), Cova de la Sarsa (Bocairent, Valencia) and Cova Fosca (Vall d'Ebo, Valencia), which together have provided the most important European collection of Cardial ceramic ware (chronoculturally diagnostic of the Early Neolithic).     

IDENTIFYING THE PLANT ORIGIN OF ARTISTS' YELLOW LAKE PIGMENTS BY ELECTROSPRAY MASS SPECTROMETRY

Dyes containing flavonoids are found in yellow lake pigments used as artists' materials. Pre‐treating a sample of a flavonoid‐based lake pigment with an acidic ion exchange resin followed by reversed‐phase HPLC electrospray mass spectrometry enables the identification of key diagnostic yellow compounds, even when the pigment is bound in paint media. Reference raw plant materials of weld and buckthorn berries were also treated similarly for comparison with the lake pigments derived from these plants. This method is suitable for microsamples and thus suitable for analysis of samples that can be ethically removed from works of art in the course of their conservation. The flavonoid content is analysed and plant origins are suggested for yellow lake samples taken from Reclining Tiger by Jean‐Baptiste Oudry and the 1893 version of The Scream by Edvard Munch.     

ELECTRON BACKSCATTER DIFFRACTION (EBSD): A NEW TECHNIQUE FOR THE IDENTIFICATION OF PIGMENTS AND RAW MATERIALS IN HISTORIC GLASSES AND CERAMICS

Coloured samples of glass and ceramic were selected for EBSD investigation to verify the potential (advantages and limitations) of this technique in the characterization of the raw materials used and the neoformation phases originating from the manufacturing processes. In the case of copper‐bearing red glasses, it was verified that micrometric droplets, residuals of the original copper source, can be ascribed to metallic copper or to a low‐Sn bronze, due to strongly similar lattice parameters. From the same samples, micrometric flakes were identified by EBSD as magnetite and interpreted as residues of the reducing agent used in the production of such red glasses. Further, the technique allowed the pigment responsible for the yellow colouring of some incised slipware to be recognized as bindheimite. In a third case, the black pigment, contained in some Nestorian decorated pottery, was identified as an amorphous phase of Mn oxide. The accurate identification of the colouring particles and other products or materials offered a more precise comprehension of the production technique, period and site of the examined artefacts, together with scientific parameters for the identification of the raw materials, their transformation during the production cycle and an evaluation of the most reliable recipes used for their preparation.     

SYNTHESIS AND ACID RESISTANCE OF MAYA BLUE PIGMENT*

Maya blue is an organo‐clay artificial pigment composed of indigo and palygorskite. It was invented and frequently used in Mesoamerica in ancient times (eighth to 16th centuries). We analyse in this paper one of the characteristics of Maya blue that has attracted the attention of scientists since its rediscovery in 1931: its high stability against chemical aggression (acids, alkalis, solvents, etc.) and biodegradation, which has permitted the survival of many works of art for centuries in hostile environments, such as the tropical forest. We have reproduced the different methods proposed to produce a synthetic pigment with the characteristics of the ancient Maya blue. The stability of the pigments produced using either palygorskite or sepiolite has been analysed by performing acid attacks of different intensities. The results are analysed in terms of pigment decolouration and destruction of the clay lattice, revealed by X‐ray diffraction. Palygorskite pigments are much more resistant than sepiolite pigments. It is shown that indigo does not protect the clay lattice against acid aggression. We show that Maya blue is an extremely resistant pigment, but it can be destroyed using very intense acid treatment under reflux.