Early Islamic Pottery Materials and Techniques

58 Pages·2003·20.812 MB·English

by  Anne-Marie Keblow Bernsted

Early Islamic Pottery
Materials and Techniques
Anne-Marie Keblow Bernsted
Contents
First published 2003 by Archetype Publications Ltd.
Archetype Publications Ltd.
6 Fitzroy Square
Preface V
London W1 T 5HJ
www.archetype.co. uk Acknowledgements VI
Tel: [phone] Introduction VII
Fax: [phone]
Ceramic raw materials and techniques
Note: The right of Anne-Marie Keblow Bernsted to be identified as the author Unglazed, pre-Islamic pottery
of this work has been asserted by her in accordance with the Copyright, Designs
Early glazes
and Patents _Act 1988.
2
White-ground decoration
© 2003 Anne-Marie Keblow Bernsted 4
Inglaze colours
7
ISBN 1-873132-98-0 Lustre ware
11
Slip-painted ware (Nishapur type)
British Library Cataloguing in Publication Data
19
A catalogue record for this book is available from the British Library. Slip-painted ware (Garms type)
23
Fritware
All rights reserved. No part of this publication may be reproduced, stored in a
28
retrieval system, or transmitted, in any form or by any means, electronic, Silhouette ware
mechanical, photocopying, recording or otherwise, without the prior permission 39
Raqqa ware
of the publishers.
40
Laqabi ware
Front cover illustration: Fritware tile covered with cobalt blue glaze and 42
Relief-moulded ware
decorated with white lead, iron oxide and gold leaf (diameter: 20.1 cm). Tile
44
deposited at The David Collection 45/1986. (Photo: A.M. Keblow Bernsted) Minai ware
Back cover illustrations: Fritware dish painted with chromite black under so
Lajvardina ware
clear copper turquoise alkaline glaze (height: 10.5 cm; diameter 37.0 cm). The
David Collection 5/1970. Sketch of fritware dish DS 5/1970. (Photo and sketch: Kilns 53
A.M. Keblow Bernsted)
Chemical and petrographic investigation of the pottery 61
61
Techniques and methods
Printed on acid-free paper. 62
Clay properties
63
Designed and typeset by PDQ Digital Solutions Ltd., Bungay, Suffolk The Iraqi ware
Printed and bound in Great Britain 65
The Iraqi clay
by Henry Ling Ltd., The Dorset Press, Dorchester
68
The Egyptian ware
Preface
The Egyptian clay 70 The aim of this book is to make the pottery of the early derived from investigations of Islamic pottery glazes and
Islam.ic period accessible to those who might be interested pigments.
The Syrian ware 73
i11 the ceramic techniques, including those applying to In the second section - Kilns - a kiln characteristic of
The Syrian clay 78
pigments, glazes and body. This pottery is today almost the period is described.
The Persian ware 79 t:xclusively found in museums and thus can usually be The third section - Chemical and petrographic investi
enjoyed by the museum visitor only at a distance. gation ef the pottery - addresses those readers who are
The Persian clay 82
Since 1985, in my role as conservator at Davids particularly interested in ceramic materials in the form
Topography_ and occurrence of ceramic raw materials 87 Samling (The David Collection, Copenhagen), I have of the clay itself, or rather, the fired clay. The various
been responsible for the care of the collection of Islamic bodies and the development from the early yellow and
Iraq 87
pottery, which has inevitably resulted in a deeper interest red earthenware through the light-brown quartz pottery
Egypt 89 in its technical composition. Over the years I have given to the white fritware are described as well as tempering,
Syria 90 various conducted tours of Davids Sarnling, covering grain size, levigation, matrix mineralogy and firing
pottery raw materials and production techniques. These temperature.
Iran 91
tours have proved to be of great interest to potters and The fourth and final section of the book provides
Bibliography 95 kindred souls, and it is to such readers, after a brief intro information on the geographical occurrence of ceramic
duction, that the first section of the book - Ceramic raw raw materials in the areas involved in the production of
Subject index 99
111aterials and techniques - in particular should appeal. This Islamic pottery: Iraq, Egypt, Syria and Iran.
Place-name index IOI
section provides an insight into ceramic traditions with It is thus primarily technological investigations that
the aid of, among other things, a medieval Persian have been used to characterize the pottery; the historical
manuscript. The glaze recipes and methods of producing background has been treated cursorily, decoration being
pigments described are compared with the information mentioned only when it is related to technique.
V
Acknowledgements Introduction
My heartfelt thanks go to those foundations whose Royal Danish Academy of Fine Arts); Haldis Johanne There is a long, deep-rooted tradition behind the classi may thus be compared to the pigments employed in
financial support have secured the publication of this Bollingberg (Geological Institute, University of fication of archaeological pottery from the Middle East painting. The lustre pigments, on the other hand,
work: H0jesteretssagforer C. L. Davids Legat for Sl:egt og Copenhagen); J0rn Bredal-J0rgensen (The Royal on the basis of style, which is to say form and consisted of very small, colloidal particles of the elements
Venner, Grosserer L. F Foghts Fond, Becket-Fonden, Danish Academy of Fine Arts); Snorre L;ess0e decoration. In contrast, technical investigations of the gold, copper and silver.
Augustinus Fonden and Velux Fonden af 1981. Stephensen (Danmarks Design Skole) and Lucie Witte raw materials of this pottery on a chemical and The quartz-enriched white clay with added frit
I also wish to extend my gratitude to the following (Carsten Niebuhr Institute, University of Copenhagen). mineralogical basis have played a somewhat lesser role. (fused and crushed mixture of glaze components) - the
who have kindly contributed advice, support, informa Leica Microsystems A/S provided generous assistance This book aims to address the latter deficiency- to give so-called quartz-frit pottery or fritware - was an innova
tion and pr<?,Qf-reading: Gjerl0ff Roed (formerly of with digital camera equipment. the reader insight into the ceramic glazes, colouring tion in the early Islamic period. However, it could be
Royal Scandinavia A/S); P. J. Riis (formerly of The I am grateful to The David Collection and The matters and paste materials and to augment this with a said that it was a rediscovery and further development of
National Museum of Denmark); Mirjam Gelfer National Museum of Denmark for allowing me to closer evaluation of the early Islamic ceramic material the related quartz-frit pottery and fritware of antiquity
J0rgensen (The Danish Museum of Decorative Art); photograph items from their collections and make use from the 9th to the 14th centuries found during exca which, with its white ceramic paste, occupied a special
Claus-Peter Haase (Museum for Islamische Kunst, of samples. My thanks also to those private collectors of vations in the Middle East. position in respect of material and technology. The
Berlin); Ole Bj0rn Hansen (The Royal Danish Islamic pottery who allowed me to use samples. The production of pottery has, over several millennia technique, which was employed in the Middle Eastern
Academy of Fine Arts); Niels L0nsmann Iversen (The My thanks also to the translator, Peter Crabb. and in most cultures, been a very important cultural cultural field from the 7th century BC, has survived in
activity, rich in tradition. Glazes, slips and the many Iran to the present day.
Anne-Marie Keblow Bernsted possibilities of clay were already known to several An outstanding source treating the ceramic raw
ancient peoples, among them the Egyptians and materials and production methods of the Middle East is
Mesopotamians. At the beginning of the Islannc period the 700-year-old Persian manuscript dated 1301, in
(AD 622), Muslim potters created colourful ceramic which Abu'! Qasim, a member of the renowned Persian
works of art, which although they built on ancient, pre fannly of potters Abu Tahir from Kashan, gives an account
Islamic traditions, were nevertheless stylistically quite of the potters' traditions of the time. The manuscript was
independent. The potters also developed many new translated in 1935 from Persian to German by H. Ritter,
ceramic traditions requiring considerable technological J. Ruska and R. Winderlich, and in 1973 from Persian to
insight and hard-won experience. English by J. W Allan. It will in this book be adduced as
The basis for the colours of the Islamic glazes and a living picture of the early Islamic ceramic tradition,
slips was the inorganic pigments, in contrast to the which was of such great importance for the development
organic pigments (carbon compounds), which were not of pottery far beyond the Islamic sphere, and which
suitable as ceramic colourings since they burned away reached Europe via Muslim Spain.
leaving no colour. The inorganic pigments were In the quotations from Abu'l Qasim, variant readings
normally based on the elements cobalt, iron, chromium, or additional comments from a later recension (1583) are
manganese, copper, arsenic, tin, calcium and antimony, of placed within round brackets, while the present author's
which the three last also served to impart opacity. comments are placed within square brackets. The two
Although these mineral ceramic colouring matter translations are not quoted verbatim, but have been
should preferably give a bright colour to the glaze, amalgamated and in one instance re-evaluated without
several still remained after firing as unmelted grains and reference to the original Persian.
VI VII
KAZAKHSTAN
CENTRAL
CAUCASUI ASIA
BLACK SEA
Bukhara
BULGARIA • • Samarqand
• Merv
, } • l~b.riz
• Gurgan
~1'1'11S • Mashhad I
i li
• Konya Hisar ... • Teheran • ~5 /1
Aleppo • Nishapur •
• • Rayy Kabul
d Tell nise T.1kht-i Sulayman IRAN Haluane ,f • Herat
• •Qum •Tabas~
Ho 1\ Hamadan ... • Kashan
••Guran Giyan • eQamsar eAnarak
CYPRUS ~ Sialk.. • N ,.
~ • Damascus •• susa • Natanz• a in •Rum
MEDITERRANEAN SEA /0 lsfahan • Kandahar
• •Yazd
l- .J • Semirom • • Gujahr
Jerusalem Taft
•Haruz
Fars
•Kirman
••• Persepolis
lndus
• Shiraz • Qahrud
SAUDI
ARABIA BALUCHISTAN
• Medina
ARABIAN SEA
UPPER EGYPT
The Islamic World
YEMEN
... Ancient site
VIII IX
Ceramic raw materials and
techniques
Unglazed, pre-Islamic pottery was known from the ancient Egyptian and
Mesopotamia and Iran had, like ancient Egypt, a pottery Mesopotamian quartz pottery. The glazes consisted at
tradition covering thousands of years. From the onset of that time of turquoise alkaline glazes or green, yellow
the 6th millennium BC, pottery that had merely been and light brown lead glazes. It is, however, only at the
,1ir-dried was decorated with a pigmented clay slip that beginning of the Islamic period that coloured glazes
was fired on during the subsequent firing of the body - attain great importance for ceramic decoration.
this was the most widespread decoration technique in In 749, the Umayyad Dynasty was replaced by that
antiquity.The colour palette consisted ofblack to brown, of the Abbasids. The capital was transferred from the
red and white mineral compounds. late Classical ambience of Damascus to Baghdad, which
The clay body was, however, sometimes first was founded according to Oriental tradition. At the
decorated with the pigmented clay slip after it had been beginning of the 9th century, the Caliphate moved to
fired. The binder for this slip consisted of a mixture of Samarra, which lay north of Baghdad on the east bank
plaster and animal glue. The technique allowed a much of the Tigris, but the city was the capital and seat of
greater selection of colours, but because the decoration government for only a short period. The seat of the
was not fired on, it was not so durable. In this case the caliph was restored to Baghdad until the Abbasids lost
pigments consisted of yellow, green and blue, in addition control following the Mongol destruction in 1258.
to black to brown, red and white mineral compounds. In Baghdad and Samarra, ceramic art developed quite
Occupying a position between decoration with clay its own style. Excavations of Abbasid Samarra have
slip and true glaze was an extremely fine, levigated yielded important finds of the tin-glazed pottery of the
'gloss', which was even finer than clay slip. Gloss times and of imported Chinese T'ang wares (618-907);
decoration was, like the clay wash, fired on at a relatively the local tin-glazed pottery is entirely Islamic in
low temperature, in contrast to the glazes, which were character in respect of form, decoration and paste. The
fused on at high temperatures. The gloss technique was pottery had, in contrast to Chinese stoneware and
already known to Mesopotamian potters of the 5th porcelain, a fine, dense, light brown to ochre yellow
millennium BC. Knowledge of the technique was, how calcareous body corresponding to the clay along the
ever, apparently lost, until it resurfaced in Crete about rivers Euphrates and Tigris. The earliest Mesopotamian
two and a half millennia later. The colours used were red, pottery from the 6th and 5th millennia had a clay make
brown and black. up that was chemically very much like that of early
Islamic Iraqi pottery. In antiquity, the clay was either used
Early glazes as it was, or finely levigated to remove impurities, as in
The production of glazes with inorganic pigments that the early Islamic period, when the levigated clay was
did not burn off colourlessly like the organic pigments sometimes tempered with finely crushed quartz sand.
Early Islamic Pottery Ceramic raw materials and techniques
(b)
Figure 1 (a) Earthenware bowl painted with cobalt blue on an opague, white tin glaze (height: 5.5 cm; diameter: 20.5 cm).
Iraq, 9th century. DS 21/1965. (b) Sketch of the bowl profile. (Photo and sketch: A. M. Keblow Bernsted.)
Crushed alkaline glass frit was then added to make the The technique of making the clear glazes opaque
paste sinter at relatively low temperature. In this way a with tin oxide was, it would seem, not known until the
sintered and strong clay ware was obtained, based on the 9th century.
Figure 2 Scatter plot of tin-lead glaze painted with cobalt (from a fragment of the same type as DS 21/1965). (Nationalmuseets
local Iraqi clay. Although tin was one of the ancient metals, it was a
Bevaringssektion, U Schnell.)
The potters, over several thousand years, obtained rare one. Its use goes back to the time when people learnt
their clay from an area of alluvial plain dominated by to make bronze and discovered that by adding a little tin, pottery which, with a clear glaze, could make do with a The tin glaze was a raw glaze that was relatively
calcareous, loose sediments deposited by the Euphrates the properties of copper could be improved, thereby single firing. The fired clay body reveals a well-sintered simple to produce in that crushed quartz and flint were
and Tigris. Besides the alluvial clay, there were extensive obtaining a new metal superior to the known metals. Tin paste, and that the firing temperature must have been in finely ground and pasted in water with a certain amount
tracts of mud here and the characteristic saline sabkas, ore was presumably at that time obtained via the caravan the range 900-1050°C. of colloidal, very fine-grained, pale clay substance with
which to the south stood in contrast to the limestone al route from Persia and from Syria, whereas much later,
Hajara outcrops which have always been so characteristic both tin and lead ores were brought by sea from Burma
of the area. and Malaysia to the ore-poor Abbasid Iraqi plains.
Figure 1 shows the 9th-century fully developed
White-ground decoration milky white tin glaze with homogeneously distributed
From the Abbasid period we have the first attempts at tin particles and blue decoration. A preliminary, biscuit,
decoration on a white ground. The first white glazes - firing removed water and volatile impurities from the
which were actually grey-white - consisted rather of a body and thus provided a stable base onto which a slip
pale quartz-rich clay engobe covered by a transparent could be applied, but was primarily necessary because of
lead glaze, the matrix consisting of alluvial clay. The differential shrinkage ofbody and glaze.The biscuit-fired
decoration, as known from Basra and Baghdad, was bowl was dipped in tin glaze, which could then adhere
executed in the so-called 'splash' technique and restricted in a thick layer. On the dry, but still unfired tin glaze,
to green and yellow-brown colours. From here, grey decoration was carried out in the blue-colouring cobalt
white glazes are also known, which on account of pigment, suspended in water, where the glaze material
underfiring had retained a mass of air bubbles in the practically sucked in the colour. After this, the object
melt. The glazes were thus not fully fused because they with tin glaze and inglaze decoration was fired for a Figure 3 (a) Cross-section of tin glaze. Tin oxide appears as grains in the raw glaze. Natural size of section 1 mm (from a
did not receive sufficient heat, giving an opaque effect. second time, making it more costly to produce than fragment of the same type as DS 21/1965). (b) Sketch of cross-section. (Photo and sketch: A. M. Keblow Bernsted.)
3
2
Early Islamic Pottery Ceramic raw materials and techniques
Figure 4 Detail of cobalt
Figure 5 (a) Cross-section of cobalt blue inglaze decoration. Natural size of section 1 mm (from a fragment of the same type
blue inglaze decoration.
:1s OS 21/1965). (b) Sketch of cross-section. (Photo and sketch: A. M. Keblow Bernsted.)
DS 21/1965. (Photo:
A. M. Keblow Bernsted.)
the form of trace element concentrations in other occurrence of cobalt ore, like tin and lead ores, has been
the addition of tin oxide. The glaze was thus an strong oxidation the cobalt was transformed into cobalt minerals. Moreover, blue glass beads coloured with very limited.
aluminium-rich smelt which in itself was fluid. The oxide. The oxide obtained in this way, i.e. divalent and cobalt from the year 2250 have been found in ancient For the Iraqi blue-decorated pottery of the early
addition of finely ground quartz and flint raised the trivalent cobalt oxide in varying ratios, was a grey-black Iran, which was apparently at that time self-sufficient in Islamic period, cobalt was obtained from Iran or the
viscosity of the glaze. But this tin glaze was in reality powder, the so-called zciffer, which should not be this colouring matter. From Eridu in Iraq around 2000 Caucasus, where there were rich deposits. Even in our
often a lead-tin glaze, since roasting tin alone proved confused with the pigment Egyptian blue, which was a BC, cobalt-coloured glass is likewise known, but the times, cobalt has been reported from Iraq only in trace
difficult because it had a tendency to scorify to an copper compound (alkaline calcium cuprisilicate). element concentrations, where the country adjoins Syria
unattractive grey powder. Tin was therefore often The zaffer, i.e. the pure metal oxide, was commonly and Jordan and in the south, Saudi Arabia. Cobalt was
compounded with lead (see Fig. 2, p. 3). By mixing the used as a blue pigment on the white tin glaze of the thus a very expensive colouring matter. It does not occur
two metals, roughly in the ratio two parts tin to one part Abbasid Islamic pottery, whereas the deep blue naturally in the native state, but is bound to other ores,
lead, a eutectic mixture was obtained with a melting underglaze colour smalt (potassium cobaltosilicate), including those of copper and nickel, in which the cobalt
point that was lower than that of any other mixture of which was used some centuries later, was a fritted commonly makes up only about 25 g per ton of ore.
the two metals, while the oxide mixture became a white product consisting of a mixture of zaffer and a flux in the In addition to the blue inglaze colour, the fresh green
powder, 'tin ash'. By adding tin oxide, owing to the form of a clear alkaline glaze. When cobalt oxide or chromic oxide (Cr20 3) is also seen in the Abbasid tin
limited miscibility of the tin oxide phase with the other other colouring oxides were fritted, a greater range of glazed pottery, where it gave yellowish grass-greens,
glaze components, a milky white glaze with good shades was obtained within each colour group, often somewhat dull green colours (Fig. 6). The
opacity, in which the tin oxide was present in granular depending on the degree of grinding. colouring matter could in principle be produced from
form, was attained (see Fig. 3, p. 3). When zaffer was used alone, however, the strength of the mineral chromite (FeCr20 4), which formed a slag
Tin glaze also formed the substrate for the overglaze the colour was so great that it was difficult to achieve an like product when it was roasted with potassium carbon
enamel colours and is further described in that context even distribution without blue spots in the glaze (Fig. 4). ate and then, under reduction with sulphur or charcoal
on p. 49. The highly concentrated zaffer, which was applied as a in the temperature range 500--700°C. The resulting
paste, was absorbed by the glaze during the firing process product was filtered and washed, after which the matt
Inglaze colours (Fig. 5). green, insoluble chromic oxide remained as a precipitate.
The blue inglaze pigment was produced from cobalt ores, The earliest known examples of decoration with Chromium, besides copper, imparted colour to green
for example cobalt glance, cobaltite, by roasting them in cobalt were Egyptian statuettes, ornaments and amulets Figure 6 Earthenware bowl painted with cobalt blue on an glazes, but owing to its refractoriness, chromium
a plentiful supply of air. When cobaltite (cobalt from 2680 to 2530 BC. The colouring matter was opaque, white tin glaze and with chrome green splashing pigments had as a rule greater opacity - unlike copper
arsenosulphide, CoAsS) was roasted at 900°C, the volatile presumably at that time imported from Iran, since cobalt (height: 6.0 cm; diameter: 20.0 cm). Iraq, 9th century. pigments which gave the pure, clear, cool bluish-green
arsenic and sulphur could be driven off, and under the ores are largely unknown from Egypt and then only in DS 25/1973. (Photo: A. M. Keblow Bernsted.) or greenish-blue colours known particularly from
5
4
Early Islamic Pottery Ceramic raw materials and techniques
dense form of the mineral, and glazed with copper The earliest traces of this unusual technique can be
coloured blue-greenish alkaline silicate glass. The first traced back to Attica in Ancient Greece, where
true quartz pottery glazed with the same blue-greenish decoration of metallic copper in colloidal dispersion was
compound, copper frit, comes from the Neqade I fired in a reducing atmosphere onto a clay slip of
culture 3500-3200 BC and from the year 2700 BC, kaolinite. The copper-red colour, which could be
when large quantities of quartz pottery glazed with intensified with iron oxide, appeared after firing as
copper frit were produced, for, among other places, diffuse pigment particles with red centres of metallic
Ujoser's burial chamber in the step pyramid at Saqqara. copper.
Ancient Egypt was abundantly self-sufficient in The technique (Fig. 8), which in the Islamic cultural
copper ore. Copper mines were found in several places sphere is presumed to have originated with the Egyptian
including Sinai's Wadi Maghagha and along the east coast glass-makers, turns up again after the fall of the Abbasid
in Wadi Dara and Wadi Gasus. In other parts of the Empire in Fa timid (909-1171) Egypt. Here the city of
:mcient world, the mountains of Oman also supplied al-Qahira (present-day Cairo) was founded. The city
copper ore, which was transformed into copper bars that became the capital of the new dynasty, and centred in al
were transported to the coast and thence shipped to Fustat, the oldest part of the city where the first Egyptian
cps
Mesopotamia. mosque was built, the potters continued the tradition
In the early Islamic period, both cobalt and copper inherited from Basra, Baghdad and Samarra. From
K
ore were imported to Iraq from Persia.According to the Fustat, lustre decoration is known on transparent lead
Arab geographer Ibn Hawqal, at that time the Persian and alkaline glazes over a white quartz-rich clay slip and
copper mines at Kashan, Tus, Kirman, Teheran and on opaque lead-tin raw glazes.The clay paste was oflocal
lsfahan, and in Bukhara and Fergana (Uzbekistan) were origin. The paste materials range here from the yellow
the most important for the Arabian caliphs. The flat calcareous clay (brick earth) and deep-red, lime-poor
Iraqi plain was, unlike mountainous Persia, not rich in mud of the Egyptian Nile to Nile clay enriched with
Figure 7 (a) Fragment of
ore, although copper mines were known there as early
4 earthenware painted with
as 1600 BC at what is now Kirkuk on the Great Zab
cobalt blue and copper-green
u b blue on an opaque, white tin nver.
glaze. DS Sf/1985. (b) Detail of Despite the fact that Syria had such rich deposits of
DS Sf/1985. copper ore at Retenu and Djahi that they could export
2
(Photo:A. M. Keblow Bernsted.)
some of the production in the early Islamic period,
(c) Energy-dispersive X-ray
Persia was at that time probably the main supplier in the
analysis (EDX) of greenish
Pb entire Middle East of the cobalt and copper glaze
Pi? Pb (green-blue) painting on tin
Pb Pb . glaze. Detail of DS Sf/ 1985, pigments that were in demand everywhere.
(Nationalmuseets Chromium ore occurred in the rocks found through
0 5 10 15
(c) Energy (keV) Bevaringssektion, U Schnell.) out the whole of Syria, Iraq and Iran. Chromium is often
found naturally bound to iron.The black mineral chrome
ancient Egyptian quartz pottery and from 12th- and about 850-900°C to sintered crystalline aggregates ironstone or chromite (FeCr204) is the only chromium
13th-century Seljuk quartz-frit pottery and fritware.The rather than glass. The balls of pigment could later be put ore of importance.
Abbasid pottery also makes use of the cool green-blue into clay crucibles and melted to a glass. The red-hot
copper pigment (Fig. 7 a-c). glass melt was shock-cooled in cold water and deposited Lustre ware
When copper was to be extracted from sulphurous as the pigment powder that could be used for ceramic Under the Abbasid Caliphate in the 9th century, the
ores, the sulphides had first, as with cobalt ores, to be decoration, giving the characteristic green-blue colour. Iraqi potters had also introduced what was known as
transformed into oxides by roasting. Copper oxide The earliest use of copper glaze is found in lustre pottery, the metallic, lustrous decoration of which
(cupric oxide), sand, soda, and lime were mixed, as was prehistoric Egyptian beads from 4400-3800, found at consisted of small colloidal particles of the elements
Figure 8 Earthenware dish painted with red-brown lustre
the practice since Egyptian antiquity, and made into the cemetery of the Badari folk south of Asyut. The gold, silver and copper.
on an opaque, white tin glaze. Egypt, 11th century to first
balls, the so-called Egyptian blue, alkaline calcium beads were made from the mineral talc (hydrated The lustre technique was one of the major half of the 12th century. DS 48/1977.
cuprisilicate (CaSi20 5. CuSi20 5). The mix was roasted at magnesium silicate) in the form of steatite, which is a contributions to ceramic art in the early Islamic period. (Photo:A. M. Keblow Bernsted.)
6 7