Michael Tite | University of Oxford (original) (raw)

Papers by Michael Tite

Archaeometry 36: 77-91, 1994

Archaeometry, 1998

Transparent high lead and tin-opacified lead-alkali glazes have been extensively used throughout ... more Transparent high lead and tin-opacified lead-alkali glazes have been extensively used throughout Europe and the Near East from their first appearance in the Roman era and the tenth- to eleventh-century Islamic world, respectively, up until the present day. Using, to a large extent, information which is widely scattered through a diverse range of literature, the methods employed in the production of these two glaze types are first outlined and their merits are then compared with those of alkali glazes in terms of ease of preparation of the glaze mixture, ease of application of the glaze, ease of firing, cost of production, glaze-body fit and visual appearance. The principal advantages of transparent high lead glazes as compared to alkali glazes are shown to be ease of preparation and application of the glaze suspension, low susceptibility to glaze ‘crazing’ and ‘crawling’ and high, optical brilliance. Factors that influence the choice of tin-opacified lead-alkali glazes include ease of production of tin oxide by melting tin and lead metals together; a reduced risk of reduction of lead oxide to lead metal and consequent blackening of the glaze; and, again, low susceptibility to ‘crazing’ and ‘crawling’. Limits of current knowledge regarding these two glaze types and requirements for future research are outlined.

Journal of Archaeological Science (97), 2018

It has been generally accepted that the beginnings of tin-based opacification of ceramic glazes i... more It has been generally accepted that the beginnings of tin-based opacification of ceramic glazes is associated with the white glazed wares excavated in Iraq and western Iran and dated to the ninth century AD (so-called 'Samarra-type' pottery). This paper focuses on an earlier stage in the technological development of tin-opacified glazes, that is, the yellow and white glazed wares produced from the eighth century AD in Egypt and the Levant. In addition, the compositional data was extended for the subsequent spread of tin-opacified glazes into Mesopotamia in the ninth century and Northern Iran and Central Asia in the tenth century. Using SEM-EDS and SR-Micro-XRD, the chemical composition and microstructure of eighty-five samples of opaque yellow and white glazed wares from Egypt (Fustat), the Levant (Madaba, Aqaba, Al-Mina and Raqqa), Mesopotamia (Samarra, Kish, Basra and Susa), Northern Iran (Takht-i Suleiman), and Central Asia (Nishapur, Merv and Samarqand) were investigated. These data confirmed that the yellow and white glazes were opacified by lead-tin-oxide (PbSnO 3) and tin oxide (SnO 2) particles respectively. Replication experiments were then conducted to imitate typical compositions of the analysed opaque yellow and opaque white glazes. Overall, the results posited the beginning of tin-based opacification of glazes in the eighth century in Egypt and the Levant, and provided explanations as to how the production of opaque yellow and white glazes in the Levant and Mesopotamia might have been technologically linked.

Journal of Archaeological Science, 2008

In this paper the study of four significant lustre samples covering 9th century AD polychrome and... more In this paper the study of four significant lustre samples covering 9th century AD polychrome and 10th century AD monochrome lustre from Iraq is presented. The samples selected are representative of the earliest known lustre productions. The data obtained from the study of the medieval samples are compared to laboratory reproductions and gives important clues about the invention, perfection and success of lustre during this period. The change from polychrome to monochrome lustre decorations and the increase in the lead content of the glazes are the key parameters in the success of obtaining a golden lustre.

Quaternary Science Reviews, 2001

Both the AMS radiocarbon technique and TL dating have been used to study the age of organic-tempe... more Both the AMS radiocarbon technique and TL dating have been used to study the age of organic-tempered pottery from Gasya, one of the earliest Neolithic sites in the Russian Far East. The results obtained are consistent with the previous set of radiocarbon dates from the site, that were obtained for charcoal, and show that the hypothesis that the earliest pottery from the Amur River basin dates to before 10,000 BP (calendar years) is valid. The organic-tempered pottery from the Russian Far East therefore looks promising for future dating by the AMS radiocarbon and TL methods.

Journal of Cultural Heritage, 2008

Replications of the lustre layers have been produced using laboratory-controlled conditions, base... more Replications of the lustre layers have been produced using laboratory-controlled conditions, based on a 13th century AD lustre recipe. The characteristics of the lustre layers obtained by using different paint and glaze compositions, thermal paths and atmospheres are summarised.

Journal of Archaeological Science, 2007

The chemical compositions and microstructures of some 35 faience objects from Egypt spanning the ... more 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.

A broad selection of Roman lead-glazed pottery dating from the first century ad through the fifth... more 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.

Accounts of chemical research, Jan 1, 2002

In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were firs... more In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were first produced from about the 4th millennium B.C. Subsequently, the period around 1500 BC saw major developments in the range of vitreous materials with the production of glass vessels and glazed clay objects and an extension in the range of colorants used. This paper first describes how the examination of artifacts has been used to reconstruct the processes involved in the production of these different vitreous materials. This information is then used to try to understand how the new technologies were discovered and why they were adopted.

Archaeometry, 2004

Previous research has established that Iznik pottery differs from other Islamic stonepaste potter... more Previous research has established that Iznik pottery differs from other Islamic stonepaste pottery in that its stonepaste bodies contain lead oxide as well as soda and lime, and that a significant proportion of the tin oxide in its glaze is present in solution rather than as tin oxide particles. In order to better understand these distinguishing features, the chemical compositions and microstructures of Iznik pottery and tile samples, together with those of lumps of glass found in association, were investigated using both scanning electron and optical microscopy. These data have been supplemented by the study of replicate lead-alkali glazes produced in the laboratory with a range of different compositions. The results demonstrate that separate soda-lime and high-lead glasses were used in the production of Iznik stonepaste bodies, and that the total glass contents of the bodies were significantly higher than those quoted by Ab ¨ 'l-Q å sim, who was writing in about AD 1300. The very high purity of the lead-soda Iznik glazes indicated that the alkali flux used was either a purified plant ash or an as yet unidentified mineral source of soda. Replication experiments established that the high solubility of tin oxide in the glaze was due to the high purity of the glaze constituents. Furthermore, it is suggested that tin oxide was added to the glaze in order to give it a very slight opacity and thus obscure any blemishes in the underlying body.

co-authored with Tite, M. S., Shortland, A. J., and Degryse, P.

Journal of Archaeological Science, 2008

In this paper the study of four significant lustre samples covering 9th century AD polychrome and... more In this paper the study of four significant lustre samples covering 9th century AD polychrome and 10th century AD monochrome lustre from Iraq is presented. The samples selected are representative of the earliest known lustre productions. The data obtained from the study of the medieval samples are compared to laboratory reproductions and gives important clues about the invention, perfection and success of lustre during this period. The change from polychrome to monochrome lustre decorations and the increase in the lead content of the glazes are the key parameters in the success of obtaining a golden lustre.

Archaeometry, 2008

Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass producti... more Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass production for a short period in Europe from the second to the first centuries bc, and then again throughout the Roman and Byzantine Empires from the fourth century ad onwards. Tin oxide was also used in the production of Islamic opaque glazes from the ninth century ad, and subsequently in enamels applied to Islamic and Venetian glasses from the 12th century ad onwards. A selection of published analytical data for the tin-opacified glasses, enamels and glazes is summarized, and the methods used in their production are reassessed. The phase transformations occurring when mixtures of lead oxide, tin oxide and silica are fired are investigated with high temperature X-ray diffraction (XRD) using a synchrotron radiation source, and these results are used to explain the observed differences in the glass, enamel and glaze compositions. Possible reasons for the use of tin-based opacifiers in the second to first centuries bc, and for the switch from antimony- to tin-based opacifiers in the fourth century ad are suggested, and the possible contexts in which tin-based opacifiers might have been discovered are considered. The introduction of tin-opacified glazes by Islamic potters in the ninth century ad is discussed in terms of technological transfer or independent invention.

The generally accepted theory is that the demand for Islamic glazed pottery started in Abbasid Ir... more The generally accepted theory is that the demand for Islamic glazed pottery started in Abbasid Iraq in the 9th century AD with the production of a range of glazed wares in response to the import of Chinese stonewares and porcelains. However, Oliver Watson has recently proposed that the demand for Islamic glazed pottery first occurred in Egypt and Syria in the 8th century AD resulting in the production of opaque yellow decorated wares. Using a combination of SEM analysis of polished cross-sections, and surface analysis using hand-held XRF or PIXE, Coptic Glazed Ware from Egypt, Yellow Glazed Ware from Syria, and comparable wares from Samarra, Kish and Susa have been analysed. The analyses show that the opaque yellow decoration was the result of lead stannate particles in a high lead glaze, which it is suggested was produced using a lead-silica-tin mixture. The use of lead stannate in the production of yellow opaque glazes is explained in terms of technological transfer from contemporary Islamic glass- makers who continued the Byzantine tradition of glassmaking. It is further argued that the introduction of opaque yellow glazed pottery into Mesopotamia could have provided the social context for the sudden emergence of tin-opacified white glazed pottery in Abbasid Iraq in the 9th century AD. However, in view of the very different glaze compositions employed for the yellow and white opaque glazes, it seems probable that the white tin-opacified glazes used for Abbasid cobalt blue and lustre decorated wares represent a separate but parallel technological tradition with its origins in the production of Islamic opaque white glass.

The microstructures and chemical compositions of some 15 faience objects from Crete spanning the ... more 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 yellowgreen and greenish turquoise.

Archaeometry, 2007

Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass producti... more Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass production for a short period in Europe from the second to the first centuries bc, and then again throughout the Roman and Byzantine Empires from the fourth century ad onwards. Tin oxide was also used in the production of Islamic opaque glazes from the ninth century ad, and subsequently in enamels applied to Islamic and Venetian glasses from the 12th century ad onwards. A selection of published analytical data for the tin-opacified glasses, enamels and glazes is summarized, and the methods used in their production are reassessed. The phase transformations occurring when mixtures of lead oxide, tin oxide and silica are fired are investigated with high temperature X-ray diffraction (XRD) using a synchrotron radiation source, and these results are used to explain the observed differences in the glass, enamel and glaze compositions. Possible reasons for the use of tin-based opacifiers in the second to first centuries bc, and for the switch from antimony- to tin-based opacifiers in the fourth century ad are suggested, and the possible contexts in which tin-based opacifiers might have been discovered are considered. The introduction of tin-opacified glazes by Islamic potters in the ninth century ad is discussed in terms of technological transfer or independent invention.

Accounts of Chemical Research, 2002

In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were firs... more In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were first produced from about the 4th millennium B.C.. Subsequently, the period around 1500 BC saw major developments in the range of vitreous materials with the production of glass vessels and glazed clay objects and an extension in the range of colorants used. This paper first describes how the examination of artifacts has been used to reconstruct the processes involved in the production of these different vitreous materials. This information is then used to try to understand how the new technologies were discovered and why they were adopted. †

Journal of Archaeological Science, 2006

Natron deposits, the best known of which being those at Wadi Natrun in Egypt, have been used as t... more Natron deposits, the best known of which being those at Wadi Natrun in Egypt, have been used as the flux in the production of vitreous materials from the early 4th millennium BC onwards. In the present paper, the history of the use of natron as a flux is traced from its beginnings in the glaze of Badarian steatite beads, through its use in glass production starting in the 1st millennium BC, until its apparent shortage during the 7th to 9th centuries AD, and its subsequent replacement by plant ash during the 9th century AD. Documentary evidence for possible natron sources in Egypt, including the Wadi Natrun, and around the eastern Mediterranean is summarised, and the results of recent fieldwork at the Wadi Natrun and at al-Barnuj in the Western Nile Delta are presented. The possible reasons for the apparent shortage of natron from 7th to 9th centuries AD and its subsequent replacement by plant ash as the flux used in glass production during the 9th century AD are then considered. These include the possibility that, because of the massive scale of glass production, the demand for natron exceeded its supply; the possible effect of climatic changes; and the potentially disruptive role of political events in the Wadi NatruneDelta region.

Archaeometry, 2007

Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass producti... more Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass production for a short period in Europe from the second to the first centuries bc, and then again throughout the Roman and Byzantine Empires from the fourth century ad onwards. Tin oxide was also used in the production of Islamic opaque glazes from the ninth century ad, and subsequently in enamels applied to Islamic and Venetian glasses from the 12th century ad onwards. A selection of published analytical data for the tin-opacified glasses, enamels and glazes is summarized, and the methods used in their production are reassessed. The phase transformations occurring when mixtures of lead oxide, tin oxide and silica are fired are investigated with high temperature X-ray diffraction (XRD) using a synchrotron radiation source, and these results are used to explain the observed differences in the glass, enamel and glaze compositions. Possible reasons for the use of tin-based opacifiers in the second to first centuries bc, and for the switch from antimony- to tin-based opacifiers in the fourth century ad are suggested, and the possible contexts in which tin-based opacifiers might have been discovered are considered. The introduction of tin-opacified glazes by Islamic potters in the ninth century ad is discussed in terms of technological transfer or independent invention.

Accounts of Chemical Research, 2002

In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were firs... more In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were first produced from about the 4th millennium B.C.. Subsequently, the period around 1500 BC saw major developments in the range of vitreous materials with the production of glass vessels and glazed clay objects and an extension in the range of colorants used. This paper first describes how the examination of artifacts has been used to reconstruct the processes involved in the production of these different vitreous materials. This information is then used to try to understand how the new technologies were discovered and why they were adopted. †

Archaeometry 36: 77-91, 1994

Archaeometry, 1998

Transparent high lead and tin-opacified lead-alkali glazes have been extensively used throughout ... more Transparent high lead and tin-opacified lead-alkali glazes have been extensively used throughout Europe and the Near East from their first appearance in the Roman era and the tenth- to eleventh-century Islamic world, respectively, up until the present day. Using, to a large extent, information which is widely scattered through a diverse range of literature, the methods employed in the production of these two glaze types are first outlined and their merits are then compared with those of alkali glazes in terms of ease of preparation of the glaze mixture, ease of application of the glaze, ease of firing, cost of production, glaze-body fit and visual appearance. The principal advantages of transparent high lead glazes as compared to alkali glazes are shown to be ease of preparation and application of the glaze suspension, low susceptibility to glaze ‘crazing’ and ‘crawling’ and high, optical brilliance. Factors that influence the choice of tin-opacified lead-alkali glazes include ease of production of tin oxide by melting tin and lead metals together; a reduced risk of reduction of lead oxide to lead metal and consequent blackening of the glaze; and, again, low susceptibility to ‘crazing’ and ‘crawling’. Limits of current knowledge regarding these two glaze types and requirements for future research are outlined.

Journal of Archaeological Science (97), 2018

It has been generally accepted that the beginnings of tin-based opacification of ceramic glazes i... more It has been generally accepted that the beginnings of tin-based opacification of ceramic glazes is associated with the white glazed wares excavated in Iraq and western Iran and dated to the ninth century AD (so-called 'Samarra-type' pottery). This paper focuses on an earlier stage in the technological development of tin-opacified glazes, that is, the yellow and white glazed wares produced from the eighth century AD in Egypt and the Levant. In addition, the compositional data was extended for the subsequent spread of tin-opacified glazes into Mesopotamia in the ninth century and Northern Iran and Central Asia in the tenth century. Using SEM-EDS and SR-Micro-XRD, the chemical composition and microstructure of eighty-five samples of opaque yellow and white glazed wares from Egypt (Fustat), the Levant (Madaba, Aqaba, Al-Mina and Raqqa), Mesopotamia (Samarra, Kish, Basra and Susa), Northern Iran (Takht-i Suleiman), and Central Asia (Nishapur, Merv and Samarqand) were investigated. These data confirmed that the yellow and white glazes were opacified by lead-tin-oxide (PbSnO 3) and tin oxide (SnO 2) particles respectively. Replication experiments were then conducted to imitate typical compositions of the analysed opaque yellow and opaque white glazes. Overall, the results posited the beginning of tin-based opacification of glazes in the eighth century in Egypt and the Levant, and provided explanations as to how the production of opaque yellow and white glazes in the Levant and Mesopotamia might have been technologically linked.

Journal of Archaeological Science, 2008

In this paper the study of four significant lustre samples covering 9th century AD polychrome and... more In this paper the study of four significant lustre samples covering 9th century AD polychrome and 10th century AD monochrome lustre from Iraq is presented. The samples selected are representative of the earliest known lustre productions. The data obtained from the study of the medieval samples are compared to laboratory reproductions and gives important clues about the invention, perfection and success of lustre during this period. The change from polychrome to monochrome lustre decorations and the increase in the lead content of the glazes are the key parameters in the success of obtaining a golden lustre.

Quaternary Science Reviews, 2001

Both the AMS radiocarbon technique and TL dating have been used to study the age of organic-tempe... more Both the AMS radiocarbon technique and TL dating have been used to study the age of organic-tempered pottery from Gasya, one of the earliest Neolithic sites in the Russian Far East. The results obtained are consistent with the previous set of radiocarbon dates from the site, that were obtained for charcoal, and show that the hypothesis that the earliest pottery from the Amur River basin dates to before 10,000 BP (calendar years) is valid. The organic-tempered pottery from the Russian Far East therefore looks promising for future dating by the AMS radiocarbon and TL methods.

Journal of Cultural Heritage, 2008

Replications of the lustre layers have been produced using laboratory-controlled conditions, base... more Replications of the lustre layers have been produced using laboratory-controlled conditions, based on a 13th century AD lustre recipe. The characteristics of the lustre layers obtained by using different paint and glaze compositions, thermal paths and atmospheres are summarised.

Journal of Archaeological Science, 2007

The chemical compositions and microstructures of some 35 faience objects from Egypt spanning the ... more 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.

A broad selection of Roman lead-glazed pottery dating from the first century ad through the fifth... more 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.

Accounts of chemical research, Jan 1, 2002

In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were firs... more In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were first produced from about the 4th millennium B.C. Subsequently, the period around 1500 BC saw major developments in the range of vitreous materials with the production of glass vessels and glazed clay objects and an extension in the range of colorants used. This paper first describes how the examination of artifacts has been used to reconstruct the processes involved in the production of these different vitreous materials. This information is then used to try to understand how the new technologies were discovered and why they were adopted.

Archaeometry, 2004

Previous research has established that Iznik pottery differs from other Islamic stonepaste potter... more Previous research has established that Iznik pottery differs from other Islamic stonepaste pottery in that its stonepaste bodies contain lead oxide as well as soda and lime, and that a significant proportion of the tin oxide in its glaze is present in solution rather than as tin oxide particles. In order to better understand these distinguishing features, the chemical compositions and microstructures of Iznik pottery and tile samples, together with those of lumps of glass found in association, were investigated using both scanning electron and optical microscopy. These data have been supplemented by the study of replicate lead-alkali glazes produced in the laboratory with a range of different compositions. The results demonstrate that separate soda-lime and high-lead glasses were used in the production of Iznik stonepaste bodies, and that the total glass contents of the bodies were significantly higher than those quoted by Ab ¨ 'l-Q å sim, who was writing in about AD 1300. The very high purity of the lead-soda Iznik glazes indicated that the alkali flux used was either a purified plant ash or an as yet unidentified mineral source of soda. Replication experiments established that the high solubility of tin oxide in the glaze was due to the high purity of the glaze constituents. Furthermore, it is suggested that tin oxide was added to the glaze in order to give it a very slight opacity and thus obscure any blemishes in the underlying body.

co-authored with Tite, M. S., Shortland, A. J., and Degryse, P.

Journal of Archaeological Science, 2008

In this paper the study of four significant lustre samples covering 9th century AD polychrome and... more In this paper the study of four significant lustre samples covering 9th century AD polychrome and 10th century AD monochrome lustre from Iraq is presented. The samples selected are representative of the earliest known lustre productions. The data obtained from the study of the medieval samples are compared to laboratory reproductions and gives important clues about the invention, perfection and success of lustre during this period. The change from polychrome to monochrome lustre decorations and the increase in the lead content of the glazes are the key parameters in the success of obtaining a golden lustre.

Archaeometry, 2008

Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass producti... more Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass production for a short period in Europe from the second to the first centuries bc, and then again throughout the Roman and Byzantine Empires from the fourth century ad onwards. Tin oxide was also used in the production of Islamic opaque glazes from the ninth century ad, and subsequently in enamels applied to Islamic and Venetian glasses from the 12th century ad onwards. A selection of published analytical data for the tin-opacified glasses, enamels and glazes is summarized, and the methods used in their production are reassessed. The phase transformations occurring when mixtures of lead oxide, tin oxide and silica are fired are investigated with high temperature X-ray diffraction (XRD) using a synchrotron radiation source, and these results are used to explain the observed differences in the glass, enamel and glaze compositions. Possible reasons for the use of tin-based opacifiers in the second to first centuries bc, and for the switch from antimony- to tin-based opacifiers in the fourth century ad are suggested, and the possible contexts in which tin-based opacifiers might have been discovered are considered. The introduction of tin-opacified glazes by Islamic potters in the ninth century ad is discussed in terms of technological transfer or independent invention.

The generally accepted theory is that the demand for Islamic glazed pottery started in Abbasid Ir... more The generally accepted theory is that the demand for Islamic glazed pottery started in Abbasid Iraq in the 9th century AD with the production of a range of glazed wares in response to the import of Chinese stonewares and porcelains. However, Oliver Watson has recently proposed that the demand for Islamic glazed pottery first occurred in Egypt and Syria in the 8th century AD resulting in the production of opaque yellow decorated wares. Using a combination of SEM analysis of polished cross-sections, and surface analysis using hand-held XRF or PIXE, Coptic Glazed Ware from Egypt, Yellow Glazed Ware from Syria, and comparable wares from Samarra, Kish and Susa have been analysed. The analyses show that the opaque yellow decoration was the result of lead stannate particles in a high lead glaze, which it is suggested was produced using a lead-silica-tin mixture. The use of lead stannate in the production of yellow opaque glazes is explained in terms of technological transfer from contemporary Islamic glass- makers who continued the Byzantine tradition of glassmaking. It is further argued that the introduction of opaque yellow glazed pottery into Mesopotamia could have provided the social context for the sudden emergence of tin-opacified white glazed pottery in Abbasid Iraq in the 9th century AD. However, in view of the very different glaze compositions employed for the yellow and white opaque glazes, it seems probable that the white tin-opacified glazes used for Abbasid cobalt blue and lustre decorated wares represent a separate but parallel technological tradition with its origins in the production of Islamic opaque white glass.

The microstructures and chemical compositions of some 15 faience objects from Crete spanning the ... more 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 yellowgreen and greenish turquoise.

Archaeometry, 2007

Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass producti... more Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass production for a short period in Europe from the second to the first centuries bc, and then again throughout the Roman and Byzantine Empires from the fourth century ad onwards. Tin oxide was also used in the production of Islamic opaque glazes from the ninth century ad, and subsequently in enamels applied to Islamic and Venetian glasses from the 12th century ad onwards. A selection of published analytical data for the tin-opacified glasses, enamels and glazes is summarized, and the methods used in their production are reassessed. The phase transformations occurring when mixtures of lead oxide, tin oxide and silica are fired are investigated with high temperature X-ray diffraction (XRD) using a synchrotron radiation source, and these results are used to explain the observed differences in the glass, enamel and glaze compositions. Possible reasons for the use of tin-based opacifiers in the second to first centuries bc, and for the switch from antimony- to tin-based opacifiers in the fourth century ad are suggested, and the possible contexts in which tin-based opacifiers might have been discovered are considered. The introduction of tin-opacified glazes by Islamic potters in the ninth century ad is discussed in terms of technological transfer or independent invention.

Accounts of Chemical Research, 2002

In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were firs... more In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were first produced from about the 4th millennium B.C.. Subsequently, the period around 1500 BC saw major developments in the range of vitreous materials with the production of glass vessels and glazed clay objects and an extension in the range of colorants used. This paper first describes how the examination of artifacts has been used to reconstruct the processes involved in the production of these different vitreous materials. This information is then used to try to understand how the new technologies were discovered and why they were adopted. †

Journal of Archaeological Science, 2006

Natron deposits, the best known of which being those at Wadi Natrun in Egypt, have been used as t... more Natron deposits, the best known of which being those at Wadi Natrun in Egypt, have been used as the flux in the production of vitreous materials from the early 4th millennium BC onwards. In the present paper, the history of the use of natron as a flux is traced from its beginnings in the glaze of Badarian steatite beads, through its use in glass production starting in the 1st millennium BC, until its apparent shortage during the 7th to 9th centuries AD, and its subsequent replacement by plant ash during the 9th century AD. Documentary evidence for possible natron sources in Egypt, including the Wadi Natrun, and around the eastern Mediterranean is summarised, and the results of recent fieldwork at the Wadi Natrun and at al-Barnuj in the Western Nile Delta are presented. The possible reasons for the apparent shortage of natron from 7th to 9th centuries AD and its subsequent replacement by plant ash as the flux used in glass production during the 9th century AD are then considered. These include the possibility that, because of the massive scale of glass production, the demand for natron exceeded its supply; the possible effect of climatic changes; and the potentially disruptive role of political events in the Wadi NatruneDelta region.

Archaeometry, 2007

Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass producti... more Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass production for a short period in Europe from the second to the first centuries bc, and then again throughout the Roman and Byzantine Empires from the fourth century ad onwards. Tin oxide was also used in the production of Islamic opaque glazes from the ninth century ad, and subsequently in enamels applied to Islamic and Venetian glasses from the 12th century ad onwards. A selection of published analytical data for the tin-opacified glasses, enamels and glazes is summarized, and the methods used in their production are reassessed. The phase transformations occurring when mixtures of lead oxide, tin oxide and silica are fired are investigated with high temperature X-ray diffraction (XRD) using a synchrotron radiation source, and these results are used to explain the observed differences in the glass, enamel and glaze compositions. Possible reasons for the use of tin-based opacifiers in the second to first centuries bc, and for the switch from antimony- to tin-based opacifiers in the fourth century ad are suggested, and the possible contexts in which tin-based opacifiers might have been discovered are considered. The introduction of tin-opacified glazes by Islamic potters in the ninth century ad is discussed in terms of technological transfer or independent invention.

Accounts of Chemical Research, 2002

In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were firs... more In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were first produced from about the 4th millennium B.C.. Subsequently, the period around 1500 BC saw major developments in the range of vitreous materials with the production of glass vessels and glazed clay objects and an extension in the range of colorants used. This paper first describes how the examination of artifacts has been used to reconstruct the processes involved in the production of these different vitreous materials. This information is then used to try to understand how the new technologies were discovered and why they were adopted. †

Journal of Archaeological Science, 2006

Natron deposits, the best known of which being those at Wadi Natrun in Egypt, have been used as t... more Natron deposits, the best known of which being those at Wadi Natrun in Egypt, have been used as the flux in the production of vitreous materials from the early 4th millennium BC onwards. In the present paper, the history of the use of natron as a flux is traced from its beginnings in the glaze of Badarian steatite beads, through its use in glass production starting in the 1st millennium BC, until its apparent shortage during the 7th to 9th centuries AD, and its subsequent replacement by plant ash during the 9th century AD. Documentary evidence for possible natron sources in Egypt, including the Wadi Natrun, and around the eastern Mediterranean is summarised, and the results of recent fieldwork at the Wadi Natrun and at al-Barnuj in the Western Nile Delta are presented. The possible reasons for the apparent shortage of natron from 7th to 9th centuries AD and its subsequent replacement by plant ash as the flux used in glass production during the 9th century AD are then considered. These include the possibility that, because of the massive scale of glass production, the demand for natron exceeded its supply; the possible effect of climatic changes; and the potentially disruptive role of political events in the Wadi NatruneDelta region.