A technological study of ancient faience from Egypt

The chemical compositions and microstructures of some 35 faience objects from Egypt spanning the period from the Middle Kingdom through to the 22nd dynasty are determined using analytical scanning electron microscopy. Replicate faience beads glazed in the laboratory using the efflorescence and cementation methods are similarly investigated. In efflorescence glazing, there appears to be preferential efflorescence of soda over potash, and in cementation glazing, preferential take up of potash over soda into the glaze. These data are then used to try to infer the raw materials and methods of glazing employed in the production of the ancient faience. The glaze/glass phases present in the faience differ significantly in composition from that of New Kingdom glass. This could be due either to the use of different plant ashes or to changes in the composition of the plant ashes during the production of faience and/or glass. Although it is only rarely possible to determine with certainty whether ancient faience was glazed by efflorescence, cementation or application, the observed microstructures provide an indication of the approach adopted to achieve desired performance characteristics such as strength.     

FAIENCE: AN INVESTIGATION OF THE MICROSTRUCTURES ASSOCIATED WITH THE DIFFERENT METHODS OF GLAZING

The microstructures of faience, produced in the laboratory by the direct application of the glazing mixture (both in the raw state and in the form of prefired and ground frit) and by the efflorescence and cementation glazing methods, have been studied in polished sections in the scanning electron microscope (SEM). The microstructures observed were defined in terms of (1) thickness of the surface glaze layer, (2) thickness of the glaze-core interaction layer, (3) nature of the boundary between the interaction layer and the core and (4) extent of any interstitial glass phase within the quartz core. These parameters provide the basis for distinguishing between faience made by the three principal methods of glazing used in antiquity. Hence the method used to glaze an ancient faience object can be inferred from its microstructure as observed in polished section in the SEM.     

Egyptian faience glazing by the cementation method part 2: cattle dung ash as a possible source of alkali flux

Based on our current awareness, there are three distinct primary sources of alkali flux in the ancient Egyptian faience making: natron, soda rich plant ash and the so-called ‘mixed alkali fluxes’. Whereas the nature and origin of the first two types are identified to some extent, there are more questions regarding mixed alkali fluxes. In an attempt to provide further clarification on the latter source, a series of replication experiments on the production of Egyptian faience by the cementation glazing method were conducted using cattle dung ash as the source of alkali flux. After firing at 980 °C, the appearance of the faience objects, the microstructure and the chemical composition of selected samples obtained using scanning electron microscopy/energy-dispersive spectroscopy (SEM-EDS) were investigated. The discussion has primarily focused on cattle dung ash as the most, or one of the most, available sources of ash in ancient societies and its possible use as a source of alkali flux in the production of Egyptian faience, at least by the cementation glazing method.     

甘肃张家川马家塬战国墓地M4出土料珠研究

甘肃马家塬墓地是战国晚期至秦初的西戎墓地,本研究以该墓地M4出土的料珠为研究对象,以期通过分析其成分和结构特征,讨论其工艺特征,以丰富对战国时期费昂斯的相关认识。研究使用扫描电子显微镜-能谱和激光拉曼光谱仪,分析结果显示料珠为费昂斯制品,其釉层玻璃化程度很高,经历腐蚀后熔剂流失严重,明显区别于西周时期的费昂斯制品。同时确定釉层中的一些高锡颗粒物为SnO_2,表明当时在釉层制作中加入锡石或锡粉末。该费昂斯制品应采取了直接施釉或包埋施釉工艺。研究结果可为我国费昂斯发展历程演变提供信息。     

Optical Coherence Tomography for the non-invasive investigation of the microstructure of ancient Egyptian faience

Optical Coherence Tomography (OCT) is a non-invasive subsurface 3D imaging technique based on the Michelson interferometer. The non-invasive nature of OCT and its speed of acquisition makes it possible to image large volumes of intact objects to yield a complete overview of the microstructure. The production methods for ancient Egyptian faience were first investigated using scanning electron microscopy (SEM) imaging of the microstructure in polished sections and microprobe analysis of the composition of the glass phases. These studies were based on original Egyptian faience objects and laboratory reproductions of faience beads made using three different production methods. The microstructure of the same laboratory samples and the Egyptian faience objects from the British Museum Research Laboratory Collection are re-examined using OCT. It is found that OCT virtual cross-section images can be used to group ancient faience objects into three categories on the basis of the morphology of the surface glaze layer and the glaze/core interaction layer. The OCT images correspond well with SEM images of polished sections of ancient faience objects and laboratory reproductions. The virtual cross-sections produced by OCT are somewhat limited by the penetration depth, which is affected by the high absorption coefficient of the material and, therefore, cannot always provide information on the presence or absence of interparticle glass that binds together the quartz particles in the core. Nevertheless, the top two layers are well imaged and since OCT images can be obtained rapidly and without the necessity of removing a sample, the method can be applied to a very much wider range of ancient faience objects than is possible by SEM examination of polished cross-sections. In summary, this paper examines to what extent OCT can assist the investigation of the production techniques of ancient Egyptian faience.     

CHARACTERISATION OF EARLY VITREOUS MATERIALS

The microstructure and chemical composition of a range of early vitreous materials, principally from Egypt and dating from mid-second millennium B.C. onwards, have been examined in polished section in a scanning electron microscope with attached X-ray spectrometer. Faience is defined as a material with a quartz core which contains varying amounts of interstitial glass and which is covered with alkali-based coloured glaze and frit as a polycrystalline material which is coloured throughout and has no glaze covering. The amount of interstitial glass and hence the chemical compositions of the faience cores depends on the methods of production used. Frits which, on the basis of the above definition, include Egyptian blue and glassy faience differ from faience cores in containing significantly higher concentrations of lime and copper oxide. The nature of the frit, including its colour, depends on the relative amounts of lime and copper oxide.     

An early Iron Age assemblage of faience beads from Ashkelon,Israel: chemical composition and manufacturing process

The microstructure and chemical composition of eight faience beads from an early Iron Age (12th century BCE) assemblage found in the ancient city port of Ashkelon (Israel) are determined by means of FTIR spectrometry, pXRF, microRaman and SEM-EDS analysis. The results are compared with published data of Egyptian and Near Eastern artifacts. Each sample exhibits a hue which is obtained by adding a specific colorant to the glazing mixture. A new gray chalcopyrite-manganese-based colorant was identified. Cementation glazing was most likely used in the manufacturing process of the specimens analyzed, except for the blue bead, which is an Egyptian blue frit. The results suggest that these objects represent a unique assemblage, quite different from contemporary Egyptian and Near Eastern materials, and provide new information regarding the Iron Age faience evidence in the southern Levant.     

Production Technology for Copper‐ and Cobalt‐Blue Vitreous Materials from the New Kingdom Site of Amarna—A Reappraisal*

Previously published data on the chemical compositions and microstructures of copper‐ and cobalt‐blue frit, glass and faience from the New Kingdom site of Amarna in Egypt ( Shortland 2000 ) are summarized. The data are then used to infer the raw materials and processes employed in the production of these vitreous materials. The results suggest that crushed quartz pebbles were the source of the quartz for all the materials, but that different sources of alkali, both natron and a range of plant ashes, were used in the production of each material. It seems probable that the cobalt‐rich alum colorant was pre‐treated before use by precipitating cobalt hydroxide from a solution of the alum by the addition of natron. It is further hypothesized that cobalt‐blue glass was produced by melting the cobalt‐blue frit together with additional plant ash and possibly quartz. Finally, it is suggested that, in glazing the cobalt‐blue Variant D faience first produced in the 18th Dynasty, the efflorescence or application method was selected according to object type.     

DARK AND SHINY: THE DISCOVERY OF CHROMITE IN BRONZE AGE FAIENCE*

The Late Bronze Age (1550–1200 bc ) in the Near East was a period of cultural development, international trade and technological innovation, notably in metallurgy and silicate technology. As a spin‐off of the new glass technology, new colorants were also applied to faience glazes presumably to increase their aesthetic value. Here, we report on the presence of chromite minerals in the glaze of a faience vessel from Deir ‘Alla, Jordan, 1200 years earlier than reported so far. Importantly, chromite was not only used as a greyish pigment, but also as a nucleating agent for spherulitic crystallization of augite in the amorphous glaze. These synthetic augite formations give a unique, sparkly appearance to the faience vessel, apparently imitating a metallic look. The making of such an intricate glaze and its contemporary significance reflect not only the high level but also the appreciation of innovation in that region at that time.     

An Experimental Investigation into the Accidental Invention of Ceramic Glazes

Glazed objects, mainly in the form of glazed quartz and steatite solid stones, first appeared during the fifth millennium bc . At the present time, it is generally accepted that the accidental discovery of glazing was associated with ancient copper production. However, the replication experiments already conducted on glazed stones were unable to provide a convincing explanation for the accidental invention of ceramic glazes. This paper attempts to suggest a possible explanation for the accidental invention of glazes on solid stones (i.e., steatite and quartz) during the Chalcolithic period. A series of replication experiments were undertaken and the resulting objects were examined using SEM–EDS.     

湖北宜昌万福垴遗址出土费昂斯珠科技分析与研究

湖北宜昌万福垴遗址是西周中晚期至春秋时期的以楚文化为主的遗存,以该遗址M8出土的费昂斯(faience)珠为研究对象,以期通过分析其成分和结构特征并讨论其工艺特征,丰富对长江中下游地区该时期费昂斯的相关认识。本研究使用扫描电子显微镜,分析结果显示费昂斯制品以富钾费昂斯及混合碱费昂斯为主。再依据以往发表的西周时期费昂斯制品的科技研究,结合考古发掘相关材料,试图从费昂斯器物使用方式的角度,窥视其在古人精神文明进程中的角色,反观费昂斯在中原地区的发展脉络。     

古陶瓷釉质鉴定（一）

中华民族先民在制作陶器的过程中发现,烧制陶器时的温度越高,其制成品就越坚实,越耐用,于是就想尽办法提高烧成温度。到了商代,在我国南方已经出现了小型龙窑和带有烟囱的室形窑。窑炉的改进,首先实现了我国陶器烧成温度从1000℃以下,提高到1200℃左右的技术革命。又通过无数次失败后发现,不是所有的制陶粘土都能耐高温,     

Colour in Minoan faience

The microstructures and chemical compositions of some 15 faience objects from Crete spanning the period from Middle Minoan IIIA through to Late Minoan IA are determined using analytical scanning electron microscopy. The Minoan faience is compared with replicate faience beads produced in the laboratory using various combinations of manganese, copper and iron as colorants. The alkali contents of the replicate beads are varied so that the colorants are present both as ions in a glass phase and as particulate oxides. These data are then used to try to infer the original colour of the Minoan faience, the great majority of which has suffered severe weathering during burial. The results suggest that instead of the present day “hallmark greys and browns” and “subtle greens and blues”, Minoan faience originally exhibited a wide range of colours, including bright turquoise blue, purple and violet, and pale yellow-green and greenish turquoise.     

ANTIMONATE OPAQUE GLAZE COLOURS FROM THE FAIENCE MANUFACTURE OF LE BOIS D’ÉPENSE (19TH CENTURY,NORTHEASTERN FRANCE)*

Three types of antimony‐based, opaque ceramic colours were used in the faience workshop of Le Bois d’Épense during the first decades of the 19th century; that is, yellow, tawny and green. Yellow is generated by lead antimonate crystals (Naples Yellow), which are incorporated into an uncoloured glass matrix. According to SEM–EDS measurements, these pigments contain iron. The tawny colour is the optical result of the combined presence of similar yellow, iron‐bearing lead antimonate particles in a Fe‐rich, brownish glass matrix. The green opaque colour is produced by the combination of a blue cobalt glass and yellow Pb–Sn–Fe‐antimonate crystals. Cores of zoned pigments lighten the recipes, according to which the pigments were produced. First, they were synthesized by calcination, ground and then mixed with a colourless, brown or blue glass powder. The resulting powder mixture was added to a liquid agent and used as high‐temperature ceramic colour.     

A Study of the Techniques Used to Make Laohudong Guan Ware in China in the Southern Song Dynasty

Through a combination of analysis and synthesis of Laohudong Guan ware shards from Hangzhou City in southern China, some new hypotheses concerning Guan ware manufacture can be proposed. These suggest that the complex microstructures seen in Guan ware glazes, and which contribute significantly to their jade‐like qualities, may owe much to layers of fine bubbles trapped during the glazing process. It is also proposed that the multi‐layer glazing methods used at the Guan ware kilns at Hangzhou may have helped initially to disguise the relatively coarse and ferruginous clays used for Guan ware manufacture. Once established, the layered glazing technique was used for its own sake—eventually yielding wares that could comprise more glaze than clay. Raw materials and firing temperatures were also explored for this study, and these suggest the use of porcelain‐stone/wood ash mixtures for glaze‐making, with 20–30% calcareous wood ash being the usual amounts. The average heat‐work for the glaze firing seems to have been equivalent to Orton Cone 7, giving a typical finishing temperature of ～1215°C. A single biscuit firing and a single glaze firing seem likely for most Laohudong Guan wares. Studies of the losses that occur in the preparation of calcareous wood ashes suggest that very large quantities of botanic material must have been burned to provide ash for glaze‐making at the Laohudong kiln. From the environmental perspective, a combination of thick glazes and heavy wood‐ash usage would have placed great demands on local fuel supplies.     

PRE-ISLAMIC CERAMIC GLAZES AT KISH AND NINEVEH IN IRAQ

Chemical analyses (mainly by XRF) have been made of a series of glazed pottery vessels and sherds excavated from Kish and Nineveh in Iraq, manufactured between c. 600 b.c. and a.d. 600 (also a small Islamic group from Hira). The results strongly suggest, contrary to general assumption, that lead glazing was not practised in this area at this time; that the local glazing tradition persisted unchanged for 1200 years; and that the production at different periods, or at different places, can be characterized by statistically significant variations in the glaze composition.     

SCIENTIFIC INVESTIGATION OF FAIENCE FRAGMENTS ATTRIBUTED TO THE TOWN MOSAIC AT KNOSSOS*

We analysed a faience fragment from Bristol Museum and Art Gallery, to determine whether it belonged to the Town Mosaic, excavated at Knossos. Three Town Mosaic fragments from the Ashmolean Museum, Oxford were also examined. The objects were analysed using non‐destructive variable‐pressure scanning electron microscopy with energy‐dispersive X‐ray spectrometry. The Bristol object's composition and microstructures are similar to those of the Town Mosaic samples. Our results are also comparable to those from polished samples of Minoan faience (Tite et al. 2009 ), showing that VP SEM–EDX gives reliable results without invasive sampling. Silicaceous, copper‐rich microspheres were identified for the first time in two of the Ashmolean objects.     

河南三门峡虢国墓出土西周——春秋时期费昂斯珠的分析研究

河南三门峡虢国墓是西周晚期至春秋初期的大型邦国墓地,其中M2009的六璜组玉佩上使用了费昂斯珠,作为人工制品的费昂斯珠,其材料组成和工艺特点显示了古代科技水平,利用科学分析揭示其科学价值很有意义。本研究运用扫描电子显微镜(SEM-EDX)、激光拉曼光谱(Raman)分析了四件三门峡虢国墓M2009出土的费昂斯珠的微观结构和成分。研究发现,四件费昂斯珠采用直接施釉法,釉层使用了铜离子着色,可能使用了含氯和铜的矿物。费昂斯珠的内外表层还发现了羟基磷灰石和朱砂,来自于墓主遗骸和墓葬环境。     

PRODUCTION TECHNOLOGY OF ROMAN LEAD‐GLAZED POTTERY AND ITS CONTINUANCE INTO LATE ANTIQUITY

A broad selection of Roman lead‐glazed pottery dating from the first century ad through the fifth century ad was studied to establish locations of workshops and to address their technology of production. The ceramic bodies were analysed by ICP–AES. In addition, lead isotope analysis was undertaken on a selection of glazes. These findings suggested that there were several regions responsible for the production of lead‐glazed ceramics in the western Roman world, including central Gaul, Italy and, probably, Serbia and Romania. Using the body compositions as a starting point, the glazing techniques employed by each of the potential workshops were examined using electron probe microanalysis. It was determined that there were two primary methods of glazing. The first method used lead oxide by itself applied to non‐calcareous clay bodies, and the second method used a lead oxide‐plus‐quartz mixture applied to calcareous clay bodies. Based on these data for clay composition and glazing method, transfer of technology from the Hellenistic east to the western Roman world was proposed. Likewise, the inheritance of lead‐glazing technology into late antiquity was established by making comparisons to lead‐glazed ceramics dating to the seventh to ninth centuries from Italy, the Byzantine world and Tang Dynasty China.     

PRELIMINARY TECHNICAL OBSERVATIONS ON KNOSSIAN FAIENCE

Summary This preliminary study of a large number of Knossian/Minoan faience objects in the Heraklion (HM) and the Ashmolean (AM) Museums presents observations about the technological development of Knossian faience throughout the life of the Palace. In earlier deposits, such as the Vat Room, simple inlays, beads, and a figure appear; faience became more complex in the succeeding period (Loomweight Basements) and reached its culmination in the Temple Repositories period, where complex inlays and vases and large-scale figures appear.