Blue Enamel Research Articles

Distinguishing Genuine Imperial Qing Dynasty Porcelain from Ancient Replicas by On-Site Non-Invasive XRF and Raman Spectroscopy.

The combined use of non-invasive on-site portable techniques, Raman microscopy, and X-ray fluorescence spectroscopy on seven imperial bowls and two decorated dishes, attributed to the reigns of the Kangxi, Yongzheng, Qianlong, and Daoguang emperors (Qing Dynasty), allows the identification of the coloring agents/opacifiers and composition types of the glazes and painted enamels. Particular attention is paid to the analysis of the elements used in the (blue) marks and those found in the blue, yellow, red, and honey/gilded backgrounds on which, or in reserve, a floral motif is principally drawn. The honey-colored background is made with gold nanoparticles associated with a lead- and arsenic-based flux. One of the red backgrounds is also based on gold nanoparticles, the second containing copper nanoparticles, both in lead-based silicate enamels like the blue and yellow backgrounds. Tin and arsenic are observed, but cassiterite (SnO2) is clearly observed in one of the painted decors (dish) and in A676 yellow, whereas lead (calcium/potassium) arsenate is identified in most of the enamels. Yellow color is achieved with Pb-Sn-Sb pyrochlore (Naples yellow) with various Sb contents, although green color is mainly based on lead-tin oxide mixed with blue enamel. The technical solutions appear very different from one object to another, which leads one to think that each bowl is really a unique object and not an item produced in small series. The visual examination of some marks shows that they were made in overglaze (A608, A616, A630, A672). It is obvious that different types of cobalt sources were used for the imprinting of the marks: cobalt rich in manganese for bowl A615 (Yongzheng reign), cobalt rich in arsenic for bowl A613 (but not the blue mark), cobalt with copper (A616), and cobalt rich in arsenic and copper (A672). Thus, we have a variety of cobalt sources/mixtures. The high purity of cobalt used for A677 bowl indicates a production after ~1830–1850.

Investigation of the Pigments and Glassy Matrix of Painted Enamelled Qing Dynasty Chinese Porcelains by Noninvasive On-Site Raman Microspectrometry

A selection of 15 Chinese painted enameled porcelains from the 18th century (Qing dynasty) was analyzed on-site by mobile Raman and XRF microspectroscopy. The highly prized artifacts are present in the collections of the Musée du Louvre in Paris and Musée Chinois at Fontainebleau Castle in France. In the painted enamels, pigments such as Naples yellow lead pyrochlore, hematite, manganese oxide and carbon and opacifiers such as lead arsenates were detected. The glassy matrices of the enamels mainly belonged to lead-rich and lead-alkali glass types according to the Raman spectra obtained. The glaze and body phases of the porcelain artifacts were also analyzed. The detection of lead arsenate apatite in some of the blue enamels was significant, indicating the use of arsenic-rich European cobalt ores (smalt) and possibly mixing with Asian cobalt. This characteristic phase has also been identified in French soft-paste porcelains and glass decor and high-quality Limoges enamels from the same period. Based on the shape of the Raman scattering background, the presence of colloidal gold (Au° nanoparticles) was identified in red, orange and pink enamels. Different types of Naples yellow pigments were also detected with Sb-rich, Sn-rich and mixed Sb–Sn–(Zn, Fe?) compositions in the yellow enamels. The results were compared to previous data obtained on Chinese cloisonné and painted enameled metalware and Limoges enamels as well as French enameled watches.

The composition and technology of polychrome enamels on Chinese ruby‐backed plates identified through nondestructive micro‐X‐ray fluorescence

This research presents non‐destructive analyses of Chinese enamelled copper and porcelain decorated with polychrome enamels. This study utilises two key, high‐value art works with complex enamelling in the collection of the Victoria and Albert Museum (London, UK) to elucidate the composition and technology of objects with ruby‐backed decoration. These plates date from early Qing dynasty and are associated with the Yongzheng (1723–1735) and early Qianlong (1735–1796) periods. The goal of this research is to investigate the hypothesis that ruby‐backed plates in these two mediums are decorated with the same enamels and possibly manufactured in mutual enamelling workshops, which is a current topic of debate among scholars. Ten different enamel colours and the gilding on each plate were analysed and evaluated with micro‐X‐ray fluorescence to study the opacifiers and pigments. The results show that the enamels on these two works utilise the same opacifier and the consistent pigments in the white, ruby, pink, green, yellow, turquoise green, and blue enamels. Compositional differences were identified in the underdrawings, purple enamels, and gilding. The results demonstrate that Chinese painted enamels and overglazes on porcelain share mutual technology in most, but not all, of the polychrome decoration, which impacts upon our knowledge of technological organisation in the manufacture of these objects. Micro‐X‐ray fluorescence has been shown to be an effective and robust technique for the nondestructive study of decorative surfaces in these two material types.

Pigments and glassy matrix of the 17th–18th century enamelled French watches: A non-invasive on-site Raman and pXRF study

Abstract Twelve rare watches with painted enamels, mostly produced in France, from the 17th and 18th centuries in the collections of Musee du Louvre in Paris were analysed on-site in order to characterize the materials used in their enamels and the enamelling technique. All the watches were analysed by mobile Raman microspectroscopy and five of them were also analysed by pXRF. Pigments (Naples Yellow pyrochlore, hematite, carbon, lapis lazuli, arsenic sulphide, manganese oxides), opacifiers (cassiterite, lead arsenates) and corresponding lead-rich glassy silicate matrices were identified by one or two methods. Similar to the oil painting or tempera techniques, different hues of the related enamels were obtained by mixing many colouring agents, rather than using ‘pure’ enamels as in the case of Limoges enamelled objects. Lead arsenate apatite detected in some of the 17th century blue enamels is related to the use of European arsenic-rich cobalt ores, as also characterized in the blue (soft-paste) porcelain decors and high-quality Limoges enamels. The presence of colloidal gold (Au° nanoparticles) was indirectly detected by the Raman technique in the 18th century watches and confirmed by pXRF. At least three types of Naples Yellow pigment were identified with Sb-rich, Sn-rich and mixed Sb-Sn-Fe-Zn compositions.

Changes in the body, glaze and enamel compositions of early Meissen porcelain, 1723–c.1740

The evolution of early Meissen body, glaze and colorant compositions is examined using X‐ray fluorescence spectroscopy (XRF) measurements on three artefacts that can be accurately dated to the period 1723–c.1740. The results are interpreted based on recipes recorded in the earliest documents of the Meissen archives. The pure Aue kaolinite contains low levels of Ti and can be distinguished from secondary clays, for example, clay from Colditz. The excess Ti in the glaze versus the body reported earlier and confirmed by the present authors is explained by the exclusive use of Colditz clay for the glaze, as described in the recipes before 1730, providing a terminus ante quem for Meissen porcelain exhibiting this particular asymmetry. After 1730, the presence of elevated Ti in the body could serve as a marker for the experimental admixture of clays to Aue kaolinite to alter its properties. Based on the detection of As, Ba and Bi, it is suggested that smalt from Erzgebirge was the colorant for blue enamels until at least 1725.

Non‐invasive on‐site Raman study of polychrome and white enamelled glass artefacts in imitation of porcelain assigned to Bernard Perrot and his followers

AbstractBernard Perrot produced sophisticated glass objects from ~1666–1709 in Orléans, particularly white enamelled artefacts and ruby glass. We present here the first non‐invasive Raman study of 16 polychrome and white enamelled glass artefacts that are assigned to Bernard Perrot or his followers. These glasses belong to the museum collections at Orléans and Sèvres in France. The prominent characteristic of these artefacts is their white bodies that were produced in imitation of porcelain. The small thickness of enamel applied to these glasses imposes the use of a high magnification (×200) long working distance microscope objective for Raman analysis. Pigments and opacifiers were identified, and the production technology was discussed. White opacification was found to be obtained by three compounds: calcium phosphate (bone opacification) for blown utensils, calcium antimonate for figurines, and cassiterite for thin enamels. The use of characteristic arsenic‐rich European cobalt was identified in the blue enamels with the characteristic Raman signature of lead arsenate apatite as observed for the 17th and 18th century French soft‐paste porcelains and Limoges enamels. The easy Raman detection of arsenic‐rich phases also allows on‐site identification of ruby glasses produced according to Perrot's technique (formation of Au° colloids by reaction initiated with an arsenic salt). The amount and crystallinity of calcium phosphate being variable appears to be a potential tool to discriminate between different production periods or workshops.

Studying the process of enamel powder preparation for émail champlevé by colour measurements and μ‐X‐ray mappings

Colour measurements and non‐destructive μ‐X‐ray mappings have been used for the first time in a comprehensive study of medieval émail champlevé works from different production areas in France and Germany. This approach has given a new insight into the enamel powder preparation process of the glass material used for enamelling. Colour measurements demonstrated that all production centres used glass of very similar hues, but with large differences in colour saturation. The μ‐X‐ray mapping results of blue enamels are described by a semi‐qualitative approach. Significant variations in oxide contents of lead, cobalt, manganese and antimony oxides were found. The variations suggest that more than one glass material was used to prepare the powder for enamelling. The variations in antimony and cobalt show that glass had different degrees of opacity and colour depth. The manganese and lead contents, which do not correlate with the cobalt or antimony contents, indicate that probably glass of different base compositions was used to prepare the enamel powder for one champlevé field.

Blue enamel pigment—Chemical and morphological characterization of its corrosion process

The present paper studies the corrosion mechanisms of blue enamel powder samples, immersed in water, reproduced according to historic recipes from an 18th-century manuscript. The pH increase of the electrolyte reveals an ionic exchange between the alkaline ions of the glass and the hydrogen-bearing ions of the water. With the lixiviation of the alkaline components, cobalt is influenced by other neighbouring ions, leading to a change of enamel colour. In two high-lead samples, hydrated lead white and Co2+/Co3+ spinels were identified, which explains their complete colour fade. The influence of Pb2+ ions may increase in detriment of the Co2+ ions.

Swiss Stained-Glass Panels: An Analytical Study.

The history and iconography of Swiss stained glass dating between the 16th and 18th centuries are well studied. However, the chemical and morphological characteristics of the glass and glass paints, particularly the nature of the raw materials, the provenance of the glass, and the technology used to produce it are less well understood. In this paper, we studied two sets of samples from stained-glass panels attributed to Switzerland, which date from the 16th to 17th centuries: the first set comes from Pena National Palace collection, the second from Vitrocentre Romont. The aims were to identify the materials used in the production of the glass, to find out more about their production origin and to characterize the glass paints. Both glass and the glass paints were analysed by particle-induced X-ray emission; the paints were additionally analysed by scanning electron microscopy-electron-dispersive X-ray spectroscopy (SEM-EDS). The results show that the glass from both sets was probably produced in the same region and that wood ash was used as a fluxing agent. Different recipes have been used to make the blue enamels. However, the cobalt ore used as a coloring agent in all of the blue enamels came from the mining district in Schneeberg, Germany.

Non-invasive Raman analyses of Chinese huafalang and related porcelain wares. Searching for evidence for innovative pigment technologies

Abstract Eighteen Chinese painted enamelled porcelains and three Chinese enamelled Yixing stonewares dated to the 16th to 19th centuries and kept at the Musee national des arts asiatiques-Guimet (MNAAG), have been analysed with a mobile Raman set-up to identify their enamelling technology. Different Grand Feu (leadless or lead-poor colourless and blue enamel) and Petit Feu (lead-rich red (hematite), yellow and green (Pb-Sn/Sb/X pyrochlore) and black enamels) glazes were respectively identified on wares from the wucai group, the Famille verte group, and the huafalang group. Calcium phosphate was detected in a 17th century vase as a rare opacifier. Cassiterite was identified in the light green glaze of an imperial huafalang bowl dated to the final period of the Kangxi reign (1662–1722), ca. the 1st quarter of the 18th century. Lead arsenate was identified in the blue glaze of two artefacts, a huafalang bowl and a painted enamel water dropper, and in the blue enamel of a 19th century Yixing teapot. Lead arsenate found in some of the blue enamels appears to arise from the arsenic content in Erzgebirge cobalt ores (Saxony) and not due to voluntary addition. This may prove the use of raw materials or enamel powder imported from Europe in developing these opaque colours. The use of lead arsenate as white opacifier is clear for a water dropper bearing the Yongzheng emperor's mark (r. 1723–1735). The technological palette appears different for the artefacts expected to originate from the same period and provenance (imperial workshop) which is consistent with a period of intense innovation, open to technological skill from abroad – i.e. from French/European painted enamel technology – as revealed by ancient French (Jesuits) and Chinese historical reports.

On-site Raman analysis of 17th and 18th century Limoges enamels: Implications on the European cobalt sources and the technological relationship between Limoges and Chinese enamels

Limoges enamels on metal from the 17th to 18th centuries were analysed by non-invasive Raman microspectrometry with a mobile set-up in storage at the Musee des Arts Decoratifs (Paris) in order to identify the types of glazes and pigments used and to compare them with those found in Chinese cloisonne and falangcai enamels painted on metal and porcelain from the Kangxi and Yongzheng reigns (Qing dynasty). Certain French Jesuit and Chinese historical records report exchanges of technical know-how and artefacts during this period from France to China. Particular attention is paid to the detection of lead arsenate in blue and white enamels as well as in the whitened ones. Lead arsenate appears to be formed in blue enamels due to the high arsenic content of European cobalt ores exploited during the period in question.

European cobalt sources identified in the production of Chinese famille rose porcelain

The blue pigments on 112 fragments or small objects of Qing Dynasty Chinese, 95 of underglaze blue and white and 17 overglaze enamelled porcelains were analysed by LA-ICPMS. The underglaze blues on both blue and white and polychrome objects were created with a cobalt pigment that was rich in manganese with lesser nickel and zinc. This suite of accessory elements is generally considered to be characteristic of local, Chinese, sources of pigments. However, the blue enamels were very different. The cobalt pigment here has low levels of manganese and instead is rich in nickel, zinc, arsenic and bismuth. No Chinese source of cobalt with these characteristics is known, but they closely match the elements found in the contemporary cobalt source at Erzgebirge in Germany. Textual evidence has been interpreted to suggest that some enamel pigment technologies were transferred from Europe to China, but this is the first analytical evidence to be found that an enamel pigment itself was imported. It is possible that this pigment was imported in the form of cobalt coloured glass, or smalt, which might account for its use in enamels, but not in an underglaze, where the colour might be susceptible to running. Furthermore, the European cobalt would have given a purer shade of blue than the manganese-rich Chinese cobalt.

Cobalt blue – reproduction and characterisation of blue enamel recipes from The Handmaid to the Arts by Robert Dossie

Cobalt blue – reproduction and characterisation of blue enamel recipes from The Handmaid to the Arts by Robert Dossie

Research and Development Project on the Domestic Raw Materials of Enamel for Jewelry Production

The project aims to produce quality enamel colors from locally available materials in order to reduce costs. In the course of the research, information is collected on imported enamel colors and a study is carried out on chemical compositions and quality of the colors. At the same time, there is a study on local materials which can potentially be used to produce enamel colors, starting from basic colors such as red, blue and green. The study has found that the imported enamel colors qualify as lead glass because it contains 23-28% of lead. The study has also found that red enamel (transparent) blue enamel (transparent), blue enamel (opaque), green enamel (transparent), and green enamel (opaque) have similar level of density and hardness. Red enamel (opaque) has lower level of density and hardness due to its porosity which can be observed with naked eyes. The COE level is similar for all of the tested colors because their chemical compositions are similar. The study produces quality blue and green enamel at much lower cost. Colors of the enamel are achieved by adding different metal oxide. The color blue (translucent and opaque) is from adding cobalt (Co). Chromium (Cr), manganese (Mn), iron (Fe), cobalt and copper (Cu) together produces translucent dark green, while chromium and copper (without cobalt) produces opaque as lighter green. However, it has not been able to produce red enamel yet but has requested for samples from another research project “Developing New Technology to Produce Jewelry from Synthesized Red Crystal” for further study.Keywords: Enamel; Jewelry; Glass; Local Raw Materials

17th century blue enamel on window glass from the cathedral of Christ Church, Oxford: Investigating its deterioration mechanism

Abstract A chance discovery beneath Christ Church Cathedral, Oxford has brought to light some very well-preserved 17th century van Linge enamel-painted glass fragments. Deterioration was in most cases minimal and largely limited itself to the blue areas of the fragments. Here, cracking in both the enamel and the glass surface beneath it was observed, which resulted in detachment of the painted enamel and of some of its underlying glass in the more severely affected areas. This study investigates the deterioration mechanisms involved and demonstrates that cracking was probably brought about by different levels of expansion and contraction experienced by the paint layer constituents in response to fluctuations in temperature. Differences between the thermal expansion coefficients in the enamel paint and glass are thought to induce the formation of microcracks within the enamel. Certain physical properties of the blue enamel were expected to increase these thermal expansion coefficient differences, making this colour more susceptible to deterioration, resulting in the selective detachment observed in these painted fragments.

The source of blue colour of archaeological glass and glazes: the Raman spectroscopy/SEM‐EDS answers

The founding of lapis lazuli to give blue colour to glass and glazes is more and more coming out from the most recent studies of pottery and glassware of different epochs and provenances. The recent discovery in the south of Italy (Frederick II, Melfi castle) of enamelled glass pieces including blue enamels questioned the real nature of the blue colour raw materials because the castle is built over and not far from outcrops of two volcanic rocks – haüynophire and phonolite – that contain haüyne, mineral belonging to sodalite group as lazurite, that can be blue or become blue after heating. Raman microscopy and scanning electron microscopy coupled with energy dispersive X‐ray spectroscopy were tested in order to identify the rock used as raw material and to understand if the chromophore‐bearing mineral in the artefacts could be other than lazurite. To do this, the two volcanic rocks, lapis lazuli and archaeological glass with blue enamels, were studied. In particular, temperature‐dependent Raman measurements and Raman mappings both on single lazurite and haüyne crystals and on the rocks and the enamels were carried out also in order to investigate the colouration mechanism of haüyne. The results obtained allowed to make hypotheses about the transformations occurring in haüyne with heating and about the procedures of distinguishing the raw materials. Copyright © 2014 John Wiley & Sons, Ltd.

Evolutia simbolisticii blazoanelor in cazul innobilarilor cu acordare de blazon in Transilvania, Banat si Partium in cursul secolelor XVI-XVIII. Studiu comparativ / The evolution of the Representations of the Coats of Arms in Cases of Ennoblement in Transylvania, Banat and Partium During the 16th-18th Centuries. Comparative Study

If during the 16th century the kings of Hungary and the principles of Transylvania rewarded the virtues of their subjects through the grant of diplomas with coats of arms, this praxis proliferated in the 17th century with the debut of military campaigns of the two Rákóczi principles of Transylvania. Naturally, the boost of the warriors and the reward of their faithful services could be easily done through this type of ennoblement.In time we could distinguish more stages in the process of ennoblement, from far- reaching diplomas in which are specified the services of the subjects and their virtues, followed by donations of land, with the enumeration of the situations when they could use the coat of arms, to the simple mention of the ennoblement without the description of the coat of arms.As for the coats of arms granted, with a few exceptions the blue enamel of the shields prevailed, symbolizing nobility, faith, and good morals. e natural figures and the chimeras or artificial ones are of a great variety. A frequent natural figure used is the human body in different postures, vestimentation and attitudes, whether illustrating foot soldiers or riders in armour with sword or spear, or foot soldiers dressed in green or red according to the corps they belong to; a frequent representation due to the political and military realities of the time are the heads of Turkish either cut off or skewered by the sword or spear. e natural figures from the animal world are the lion as a symbol of courage, the bear as a symbol of force, the wolf as a symbol of watchfulness and prudence. Birds frequently appear including the pigeon, the swan, the vulture, the pelican, and the crane, static or flying, holding branchs, flowers, wheat, rings, crosses or stones. As for the external ornaments of the shield, generally they use a military helmet, crowned by a royal diadem, symbolizing the authority of those who confer the coat of arms.e colours and the metals are the consecrated ones: azure as a symbol of Jupiter, gold for the sun, red as a symbol for Mars and silver as a symbol of the moon.In conclusion, the title of nobility for the “armalists” meant from a socio-economic point of view only the exemption from the taxes they owe for their houses and surroundings which due to their small sizes couldn’t bring a significant profit.Of course, the noble status and the awareness of belonging to the caste of noble, gave them the feeling of an important role than if they had continued to belong to that “statu et conditione plebea”, from which they were elevated and introduced “in coetum et numerum verorum, natorum, indubitatorum, insignitorumque Regni noştri Transilvaniae et partium Hungariae eidem annexarum nobilium” as stated in the documents.During the 18th century we witness a change in point of the representations of the coats of arms due to the evolution of the political situation and to the praxis of the ennoblement. In comparison with the relatively simple compositions specific to the ennoblements for military virtues, granted in large number to warriors of modest origin with recurrence of typical military symbols, at the ennoblement at the end of the 17th century and into the 18th century we witness a diversification of the representations and a more coherent personalization, with less frequent similarities between the coats of arms granted to different families.

Sword and Dagger Pommels Associated with the Crusades, Part II: A Technical Study

The article discusses the results of a technical study of a collection of medieval sword and dagger pommels owned by the Metropolitan Museum of Art in New York City, with particular focus given to the probable use of the lost-wax technique to create them and the conclusion that they were most likely created in Europe due to the presence of Champleve enameling. A brief overview of medieval metalwork is presented, and the pommels and their creation are described in detail. The association of the pommels with the crusades is also commented on.

Homogeneity, Composition and Deterioration of Window Glass Fragments and Paint Layers from Two Seventeenth-Century Stained Glass Windows Created by Jan de Caumont (∼1580–1659)

During the conservation of two stained glass windows by Jan de Caumont at the Abbey 't Park (Heverlee, Leuven, Belgium) small fragments were removed from eight panes for analysis. Electron microscopy with energy dispersive X-ray sprectroscopy (SEM-EDX) was used to study the microstructure of several materials in these windows, and to perform quantitative analysis of the homogeneous materials. According to the SEM-EDX analyses, the glass appeared to be homogeneous. The deteriorated regions found in the fragments contained cracks, have a fractal appearance with stratifications of 2 μm in width and contained small islands of original unleached glass. Unfortunately, SEM-EDX did not allow a reliable chemical analysis of the different stratified layers due to the limitation in lateral resolution. The vitreous paint layer on one of the fragments consisted of lead glass surrounding many SiO2 and Fe2O3 particles. The green-blue and blue enamel paint layers were made with a low-melting SiO2-K2O-PbO glass. The colouring substance for the green-blue enamel paint layer was brass (i.e. an alloy of Cu and Zn), while for the blue enamel paint layer a substance known as saffre (a roasted sulphide ore rich in cobalt) was used. The compositions of the window glass fragments were all similar and consisted of high lime–low alkali (HLLA) glass (SiO2-K2O-CaO).

THE BLUE ENAMELS IN THE BAROQUE DECORATIONS OF THE CHURCHES OF PALERMO, SICILY: FE2+‐COLOURED GLASSES FROM LIME KILNS*

Deep blue glasses coloured by octahedral Fe2+ cations are often reported as textbook examples of blue pigmentation. However, despite the possibility of laboratory synthesis under reducing conditions, to date there are no well‐reported occurrences of their production and use in the past. A thorough historical, ethnographic, mineralogical, and chemico‐physical investigation of the ‘smaltini di calcara’ from several baroque churches in Palermo, Sicily, has revealed that the blue enamels widely used for altar decorations in the 17th and 18th centuries are actually a unique case of ancient blue glasses pigmented by divalent iron cations in distorted octahedral coordination. This mixed‐alkali glass was accidentally produced under severely reducing conditions in the local kilns during production of lime.