e-PS, 2010, 7, 108-115 ISSN: 1581-9280 web edition e-PRESERVATIONScience ISSN: 1854-3928 print edition www.Morana-rtd.com published by MORANARTD d.o.o. © by M O R A N A RTD d.o.o. ARTIFICAL YELLOW PIGMENTS: PRODUCTION AND CHARACTERIZATION THROUGH SPECTROSCOPIC FULL PAPER METHODS OF ANALYSIS Claudia Pelosi1, Giorgia Agresti1, Ulderico Santamaria1, Elisabetta Mattei2 This paper is based on a presentation at Artificial yellow pigments (lead-tin yellow type I and type II, the 9th international conference of the lead antimonate yellow and lead-tin-antimony yellow) have Infrared and Raman Users’ Group (IRUG) in Buenos Aires, Argentina, 3-6 been produced, starting from various recipes and from pure March 2010. chemicals, in different experimental conditions. The prod- Guest editor: ucts were analysed using micro-Raman spectroscopy. Prof. Dr. Marta S. Maier. Differences in stoichiometric ratios, in melting tempera- 1. Tuscia University, Department of tures and in crucible typologies were examined. Other ana- Cultural Heritage, Largo dell’Università, lytical techniques were required to characterize the stoi- 01100 Viterbo (Italy). chiometric ratios of the obtained products (X-ray diffrac- 2. Tuscia University, Faculty of tion, scanning electron microscopy with energy dispersive Agriculture – Centro per l’Innovazione Tecnologica e lo Sviluppo del Territorio spectroscopy and differential thermal analysis).The results (CINTEST), Via del Paradiso 47, 01100 are analysed and discussed in terms of correlations among Viterbo (Italy). chemical composition, melting conditions and colour hue. corresponding author: [email protected] 1 Introduction Through centuries, yellows of different compositions, based on lead, tin and antimony, have been used either as opacifiers in glasses, glazes and majolicas or as paint pigments. The long period of use of lead-tin and antimony based yellow pigments led to many documents in different languages employing various names describing the same compound, for instance giallolino in the southern Author Mention of giallolino sources and massicot in “… che questo color sia propria the northern ones that Cennini prieta, nata in luogo di grande arsure di montagne ….”2 according to Kühn refer to 3 the same compound (lead- Lorenzo Lotto Zalolin, Zallolin da vasari 1 tin yellow). In southern Borghini di vetro, di Fiandra, di Venezia4 Europe artists and writers di fornace, di Fiandra, di Lomazzo regularly used the term Alemagna5 giallolino to indicate a pale Vasari giallolino e giallo di vetro6 yellow material of varied Bernardo Strozzi di vetro6 received: 10.05.2010 composition (see Table 1). accepted: 25.09.2010 specie in sfumature dal giallo al Richard Symonds rosso6 key words: The main manuscripts con- Artificial yellow pigments, Raman spec- taining recipes for the pro- Table 1: Some artists and writers who mentioned gial- troscopy, X-ray diffraction, Scanning duction of lead, tin and electron microscopy lolino in their books. 108 © by M O R A N A RTD d.o.o. antimony based yellow pigments are reported in characterized using micro Raman spectroscopy, X- Table 2. These manuscripts can be considered as ray diffraction (XRD) analysis, scanning electron the first examples of written recipes based on oral microscopy with energy dispersive spectroscopy sources and on workshop notes that the master (SEM-EDS) and differential thermal analysis glassmakers kept with great care. The problem (DTA).15 Raman spectroscopy is a very useful and arises from the transcription of these notes. In fact powerful technique for the characterization of cul- this operation was made by copyists and not by tural heritage materials owing to the facts that it expert glassmakers. So during the transcription may be used in situ, is non-destructive, has high many mistakes were made that were handed down spatial resolution and is highly specific. Moreover to us creating problems in identifying and differen- Raman spectroscopy can analyse one crystal at a tiating these yellow pigments. time, like SEM-EDS, and so evaluate the presence Pigment Manuscript Recipe of compounds with different stoichiometric ratios, like XRD, but SEM-EDS does not provide a molec- Bolognese manu- Lead-tin yellow Recipe 272 ular fingerprint for the particle under observation script (first half of the type I and type II and XRD analysis cannot analyse every single 15th century)7 Recipe 273 crystal. The produced pigments have been also different recipes for characterized by other techniques like XRD and Piccolpasso8 (1559)- the production of Passeri (1758)9 Zalulino and SEM-EDS because at present reference Raman Lead antimonate Giallolino spectra of standard pigments are not always avail- Brunoro manuscript Recipe 137 (c. 32v.) able. Moreover Raman spectra found in spectral (1645)10 Valerio Mariani from databases are sometimes referred to commercial Pesaro treatise Giallo dei vasari products that are not pure. Thus, another aim of (1620)11 this work was to discuss the Raman spectra Recipe D 60 Darduin book of obtained in our work in comparison with literature Lead, tin and recipes (about Recipe D 187 (verso) antimony yellow references and to investigate the influence of the 1644)12 Recipe D 187 (recto) experimental conditions on the chemical and phys- ical characteristics of the produced materials. Table 2: Manuscripts and treatises dealing with the production of lead-tin-antimony based pigments. A case study is also reported as comparison with the synthesized products. A full account of literary sources and manuscript recipes is beyond the aim of this paper and it can be found elsewhere.13 2 Materials and Methods The aim of this work was the production and char- Pure oxides (PbO, Pb3O4, SnO2, Sb2O3 and SiO2) acterization of artificial yellow pigments by micro- supplied by Acros (Acros Organics, New York, Raman spectroscopy and other techniques starting USA) were used for the production of lead-tin-anti- from the results obtained in previous papers.14-15 mony yellow pigments. The oxides were mixed in By analyzing the various recipes concerning lead- agate mortars and then introduced into the furnace tin-antimony yellows, it was possible to recon- at room temperature. They were heated up to the struct the original production methods of these required temperatures. According to literature pigments though the experimental conditions were data1,16-21 temperature was different depending on not clear (temperatures are not indicated, time is the typology of the pigment to be produced (670, often unspecified and materials are not clearly 800 and 900 oC for lead-tin yellow type I and type II; reported). 900 and 950 oC for lead antimonate; 925 oC for lead-tin-antimony yellow). The temperature was We produced lead-tin yellow type I (Pb SnO ) and 2 4 maintained constant for 5 h. Only for the produc- lead-tin yellow type II (PbSnO or PbSn Si O ) 3 1-x x 3 tion of lead-tin yellow type I was a time of 3 h also following the indication of recipes 272 and 273 of tested. Then the samples were allowed to cool the fifteenth century Bolognese Manuscript, lead slowly inside the furnace (see Table 3). In order to antimonate yellow (Pb Sb O ), called Naples yel- 2 2 7 evaluate the influence of cooling condition, lead- low, according to the treatises written by tin-antimony yellow was also cooled in cold water Piccolpasso, Passeri and Valerio Mariani from at 10 oC following Cascales’s instructions.16 For Pesaro, and lead-tin-antimony yellow the production of lead-tin yellows porcelain cru- (Pb SnSbO ) from the Darduin, Valerio Mariani 2 6,5 cibles were used; for lead antimonate and lead-tin- from Pesaro and other authors´ recipes.15 More antimony yellow porcelain crucibles and terracotta recent works, dealing with the production and tiles covered by filter paper were used. Each sam- analysis of artificial yellow pigments, were taken ple was identified by an alphanumeric system with into account.1,16-21 The obtained products were capital letters and numbers. The abbreviation PSA Artificial Yellow Pigments: Production and Spectroscopic Characterization, e-PS, 2010, 7, 108-115 109 www.e-PRESERVATIONScience.org indicates lead-tin yellow type I, PSB lead-tin yel- The micro-Raman spectrometer was a Labram low type II, APA lead antimonate, APSA lead-tin- Model of the Dilor JobinYvon (Jobin Yvon, Horiba antimony yellow. The abbreviations are followed Group, New Jersey USA) with a spatial resolution by a number that specifies the experimental condi- of 2 µm and the possibility of fast detecting owing tions. to the use of a CCD detector cooled to -50 oC. The exciting wavelength was the 632.8 nm red line of a The obtained products were analysed by SEM- He-Ne laser. Integration times varied between 10 EDS, XRD, DTA and micro-Raman spectroscopy. and 20 s with 5 accumulations. The laser power The SEM-EDS analysis was carried out using a was 3.2 mW. JSM 5400 system (Jeol, Tokyo, Japan) with EDS2000 electron probe micro analysis supplied by Oxford Instruments - Microanalysis System 3 Results and Discussion (Oxford Instruments, Abingdon, Oxfordshire UK, www.oxford-instruments.com) ; the crystal area Table 3 summarizes the production processes and was 10 mm2 and the work distance 22 mm. The the main characteristics of the obtained yellow pig- probe operated at 25 kV and 60 mA. ments. Each artificial yellow pigment will be dealt with separately. The X-ray analytical equipment was a Philips PW1830 diffractometer (Philips, Eindhoven, The Netherlands) with Cu tube, using the 1.5418 Å Cu- 3.1 Lead-tin yellow type I Kα radiation; operating at 40 kV accelerating volt- age and 30 mA beam current. The differential ther- Lead-tin yellow type I was produced at a tempera- o mal analysis (DTA) was performed by means of a ture of 800 C for 5 h. PSA2 is in fact the most simultaneous TGA/DSC/DTA instrument model homogeneous pigment as regards composition Q600 from TA Instruments (TA Instruments, New and colour hue (Figure 1).