C for Studio Pottery: a Systematised Development of Raw Glaze Theory and Practice for Once Fired, Midfire Purposes Ivan Oscar Englund University of Wollongong
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1995 Glazes between 1100[degrees]C and 1200[degrees]C for studio pottery: a systematised development of raw glaze theory and practice for once fired, midfire purposes Ivan Oscar Englund University of Wollongong
Recommended Citation Englund, Ivan Oscar, Glazes between 1100[degrees]C and 1200[degrees]C for studio pottery: a systematised development of raw glaze theory and practice for once fired, midfire purposes, Doctor of Philosophy thesis, Faculty of Creative Arts, University of Wollongong, 1995. http://ro.uow.edu.au/theses/1753
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GLAZES BETWEEN 1100°C AND 1200°C FOR STUDIO POTTERY A Systematised Development of Raw Glaze Theory and Practice for Once Fired, Midfire Purposes
A written submission in partial fulfilment of the requirements for the award of the degree
I UNIVERSITY Of | WOLLONGONG
DOCTOR OF CREATIVE ARTS
from
UNIVERSITY OF WOLLONGONG
by
IVAN OSCAR ENGLUND FSTC ASTC
Faculty of Creative Arts 1995 CERTIFICATION
I certify that this work has not been submitted for a degree to any other university or institution and, to the best of my knowledge and belief, contains no material previously published or written by any other person, except where due reference has been made in the text.
Ivan Oscar Englund
21 June 1995 GLAZES BETWEEN 1100°C AND 1200°C FOR STUDIO POTTERY
A Systematised Development of Raw Glaze Theory and Practice For Once Fired, Midfire Purposes
ABSTRACT
This research investigates "middle fire" ceramic glazes in the firing temperatures between 1100 and 1200 degrees centigrade (Seger cones 1 to 6). It addresses an area of firing temperatures that has been largely neglected over the centuries, in contrast to both earthenware and stoneware about which there is a vast amount of information available. The research shows, however, that there is evidence of a current growth of interest worldwide in midfiring for reasons of economy and ecology. The author's long invovement in pottery extending over forty years positions him well to develop glazes in this study which compare favourably with those in other temperature ranges.
Of added significance and originality the middle fire glazes have been developed for "once firing" or "raw glazing" where glaze is applied to the damp pot thereby eliminating the biscuit fire. Researching the literature of ceramic studio work done both in Australia and overseas has yielded no reference to this method of glaze application at the middle fire temperatures. The combination of middle firing and raw glaze application is worthy of consideration because each part of the process saves on fuel consumption. There is a saving in costs for the potter and there are benefits to the ecology with less fossil fuels used, less greenhouse gasses created and less contribution to the possible global warming.
The dissertation is of necessity a technical paper put into perspective by a brief examination of the history of glazes, as seen from the viewpoint of a potter as opposed to the traditional archaeological viewpoint. Early pottery from the Middle East, China, Japan, Korea and Europe are considered. The links between these Asian and European traditions and Australian ceramics, introduced by Bernard Leach with the publication of his A Potter's Book, are described as the basis of Australian glaze traditions.
Recipes for raw glazes firing at Seger cones 1 to 6 are listed together with descriptions of the fired results and Seger formula calculations. Table of Contents
1 Introduction 1
2 The Earliest Pottery - A Brief Historical Survey 3
Western History 5
Eastern History 9
European Lustre Ware 22
European Tin Glaze 24
3 Industrialisation and Studio Pottery 26
The Leach Contribution 28
The Australian Scene 30
4 The Middle Fire Glazes 49
5 Working the Seger Formula 55
6 Bentonite and Once-Fired Glazes 61
Raw Glazes for Reduction and Oxidised Once Fired Purposes 69
8 Bibliography
9 Appendix 1 - Glaze Calculations
10 Appendix 2 - Clay
11 Appendix 3 - The Exhibition ACKNOWLEDGEMENTS
Beryl Margaret Anderson
Professor Sharon Bell
Dennis Chapman
Professor Barry Conyngham
Annette Diamant
Lindsay Duncan
Professor Peter Fielding
Dr Bert Flugelman
Ian Gentle
Andrew Hunter
Sandra Indlekofer-O'Sullivan
Elizabeth Jeneid
Daniel Midwinter-Hampton
Dr Sue Rowley
Dr Peter Shepherd
Julia St George
The Walcha Telecottage
Allan and Leslie Wickham Chapter 1
INTRODUCTION
GLAZES BETWEEN 1100°C AND 1200°C FOR STUDIO POTTERY:
A Systematic Development of Raw Glaze Theory and Practice for Once Fired, Midfire Purposes
This research investigates "middle fire" ceramic glazes in the firing temperatures between 1100 and 1200 degrees centigrade (Seger cones 1 to 6). In my opinion this area of firing temperatures has been largely neglected over the centuries in contrast to both earthenware and stoneware, about which there is vast amount of information available. My research shows, however, that there is evidence of a current growth of interest worldwide in mid-firing for reasons of economy and ecology. Because of my long invovement in pottery extending over forty years I am in a position to authoritatively evolve glazes in this study which will compare favourably with those in other temperature ranges and that will be as attractive to potters as are the more traditional glazes in the low fire earthenware area and in the high temperature field of stoneware. I have therefore extended my earlier work on cone 4 glazes to cover the completefiring rang e between cones 1 and 6.
Of added significance and originality my middle fire glazes have been developed for "once firing" or "raw glazing" where glaze is applied to the damp pot thereby eliminating the biscuitfire. M y research into the literature of ceramic studio work done both in Australia and overseas has yielded no reference to this method of glaze application at these middle fire temperatures. I regard the combination of middle firing and raw glaze application as very important, as each part of the process saves on fuel consumption. There is a saving in costs for the potter and there are benefits to the ecology with less fossil fuels used, less greenhouse gases created and less contribution to the possible global wanning.
I regard this study to be an important contribution to the expansion of knowledge in the very long history of ceramics. This dissertation is of necessity a technical paper put into perspective by a brief examination of the history of glazes, as seen 2 from the viewpoint of a potter as opposed to the more traditional archaeological viewpoint. The earliest pottery known from the Middle East is examined and contrasted with the Chinese wares from Shang to Ming dynasties, the Japanese and Korean potteries andfinally wit h the European lustre and tin glazed wares.
The Australian colonies depended largely on European ceramic technology until the publication of his A Potter's Book by Bernard Leach.1 His writings about his work with Hamada in Japan and his own experience of stoneware in Britain raised the Australian awareness of the importance of the Song wares and the place that high fired wares such as porcelain and stoneware could play in the work of studio potters. The Leach/Hamada tradition was sewn into the post-war Australian art evolution by potters such as Ivan McMeekin, Mollie Douglas, Peter Rushforth and myself. Our collaboration founded the Potters' Society of Australia, a significant influence in disseminating knowledge to Australian potters and fostering the growth of serious studio pottery through discussion groups, lectures and workshops. Each one of our four separate career paths is described. My special involvement in mid-fire raw glazing and my research in developing suitable glazes forms the focus of this dissertation.
I have used the Seger formula method of evolving glazes and this is described in detail. I have illustrated its use with an example of a glaze based on a eutectic which melts at 1160 degrees centigrade the formula of which is 1 CaO, .35 AI2O3, 2.48 Si02- I have then tabled calculations to incorporate bentonite as the key variable component for glazes to be applied to the leather hard pots, the so-called oncefire o r raw glaze method.
Recipes for raw glazes firing at Seger cones 1 to 6 are listed together with description of the fired results and the complete Seger fomula calculations for the above glazes are given as tables in Appendix 1. In Appendix 2 some commercial clays suitable for firing at these temperatures are discussed together with some body recipes for potters who wish to make their own and in Appendix 3 are details of my Exhibition at the Bloomfield Galleries, Paddington which showed pots using some of the glazes from this study.
Old age hath yet his honour and his toil. Death closes all; but something ere the end, Some work of noble note, may yet be done ...
(Tennyson)
Bernard Leach. A Potter's Book. Faber and Faber, London, 1940. 3
Chapter 2
THE EARLIEST POTTERY - A BRIEF HISTORICAL SURVEY.
In approaching almost any matter relating to pottery and especially that involving research there is an overwhelming sense of the vast history of the subject. Making pottery was one of the earliest crafts, along with basket making, weaving, the making of weapons, undertaken long ago in prehistory. One can speculate with regard to weapons that it seems likely that a stick may have been used for defence or attack and this could logically have evolved into a spear for throwing or jabbing by sharpening it into a point. Perhaps by chance it would have been found that the point could have been improved by hardening in a fire. Further improvements may have followed by attaching a hard, sharp stone flake to the tip to further improve the efficiency of the spear, and it follows that over the centuries spear points would be made of bronze then iron and steel.
Similar speculation suggests that baskets probably evolved as containers for food and the transport of various items. Food may have been placed on a bed of grass or reeds. Possibly by some chance it was noticed that interweaving the reeds resulted in a firmer grass bed and so a transportable carrier bag evolved. During a visit to Papua New Guinea in 19811 saw such bags being made. Interlacing reeds or grass was probably the forerunner of weaving of other fibres. Reed mats could have been made as part of the hut-building process and asfibres became available weaving as we understand it would have gradually come into being. Making cloth to augment or replace animal skins as clothing is a likely motivator.
Some authorities suggest that clay may have been used to smear into baskets to fill the gaps between the fibres to make the utensil more useful for storing small grains. The next step may have been the accidental burning of the basket in the cooking fire, resulting in the hardening of the clay into a crude ceramic pot. There is some perception that this may have been the case because many of the earliest pots still in existence are decorated by criss-cross patterns, either incised or painted with coloured pigments thought to have been related to baskets. Another suggestion is that a fire may have been lit on a clay area and the hardness of the ground after it cooled could have been observed as useful. Clay was used for various decorative purposes such as body painting, cave painting and weapon painting so it would have been a familiar material in many parts of the world. 4
Western History I have used Cox's Pottery and Porcelain1 as my main reference for this early history. In addition, much of my data has been acquired and accumulated along the way, sometimes serendipitously, over my years as an artist. For these 'facts' there may be no quotable source. As investigations by historians and archaeologists continue in all parts of the world new information is collected. A great deal of our knowledge of the ancient past comes from the excavations of pots and pottery shards for, though baked clay or potteiy is comparatively fragile and easily broken, it will survive better than many other materials as an indicator of a past civilisation. The question of where pottery was first made will probably never be answered though some authorities suggest that at least some of the earliest pottery was discovered during excavations in the 1960s at Catalhuyuk in Turkey on the Anatolian Plateau. By reference to the various levels of the excavations this was calculated to be about 9000 years old. The Encyclopaedia Britannica3 describes the wares as being a crude soft earthenware and notes that a more advanced variety of handmade ware dating at about 6500BC has been found in the same area. This ware was burnished and fired higher resulting in a harder material. The pots were not glazed but those that were burnished had a sheen on the surface, achieved by rubbing the clay while it is still damp but quite firm with a smooth pebble or some other very smooth object. The longer the burnishing the greater the sheen which remains when the pot is dry and after it is fired. Even today this method is used by some studio potters who prefer a natural sheen on the clay to a glazed surface. This sophisticated treatment of a clay surface in the Neolithic Age would seem to indicate that pots had been made for a long period of time previously, for the method is one that suggests an evolution over time. Also it is something that is discovered with experience. Again the report that the pots from these excavations were harder indicating a higher temperature is another reason for suspecting that their making had been preceded by many generations of potters who had succeeded in some way in making their kilns efficient enough to reach the required temperatures.
The crude, soft earthenware from the digs at Catalhuyuk would point to the fact that the firing technique was very primitive, probably in some sort of open bonfire or a simple pit. Even today potters use such methods. In Fiji I saw village women fire a single dry pot in a small open fire fuelled by a few coconut husks. This resulted in a soft porous pot. After lifting it from the fire with a stick the potter rubbed the interior with resin from a special tree. The resin melted with the
2Warren E Cox. Pottery and Porcelain, Crown Publishers, NY, 1949. ^Encyclopaedia Britannica, 1982 edition. 5 heat, covering the clay surface with an impervious layer. This sort of primitive firing is adopted by some 'pseudo-primitive' modem potters who find the results satisfy the aesthetic goals they set themselves, using pit and sagar firing methods. The pit firing can result in various 'natural' colours, achieved by the variations of heat from the burning wood. However, it is amusing to note that often the inherent properties of 'softness' and fragility of the clay fired in such a way are avoided by a preliminary biscuit firing, perhaps in an electric kiln, and the 'accidental' colours yielded by burning wood are augmented by applications of coloured slips and washes of oxides, particularly copper and iron and a sheen is added by polishing thefinished po t with wax.
Cox in his Pottery and Porcelain* noted that A J Butler reported some tiles with a blue-green glaze and inlaid hieroglyphics made in Egypt about 5500BC. Cox also claims that Egypt was probably the area where glazes werefirst evolve d and used. This is supported by the fact that blue-green glazes or turquoise glazes have been the hallmark of all so-called Middle East countries, with examples from Egypt, Persia and Turkey. In fact even today these coloured glazes are often called Egyptian blue or sometimes Mohammedan blue. The turquoise colour in a glaze is achieved by adding a small amount of copper, in the form of copper oxide, copper carbonate or even copper metal filings to a highly alkaline glaze. In Egypt and Arabia, and other arid areas in Australia, Africa and the USA, there are many playas and salt pans where brines evaporate and deposit minerals in the form of chlorides, sulphates and carbonates. It is therefore feasible to consider the development of primitive glazes and glasses in the Middle East involving the sodium rich evaporative minerals coloured by copper.
Petrie5 reported very early pots from the Middle East made of fine clay with a black surface found to be iron ore. Such pots would probably have beenfired a t earthenware temperatures of about one thousand degrees Centigrade. In Southwest Iran pottery dating from 3200BC has been found. These goblets, vases and bowls were mostly painted in a geometric style with dark colours, probably clay slip or ground iron-rich rocks. Antediluvian archaeological digs have yielded decorated, wheel-thrown pottery, called 'Al'Ubaid'. According to the Bible the Great Flood is usually thought to have occurred about 3000BC.
In Europe a great variety of pottery has been found from kitchen middens. Many of the shapes have rounded or pointed bottoms, suggesting that they were made to
4Cox, p. 153. ^Flinders Petrie, in Cox, p. 9. 6
sit more firmly on uneven ground or on cave floors. Evidence of these shapes is universal in early civilisations. Archaeologists pay great attention to the decoration on pots, perhaps more than to the clays and the making and firing techniques, so firing temperatures are rarely mentioned. It has been noted through history that decoration is added to almost eveiy thing that has been made by humans. There seems to be an inherent need to embellish an otherwise perfectly functional article, be it a weapon, a shelter, clothing or a pot. Suzanne Foley sees clay as a particularly seductive material and feels the, "expansion of work in ceramic art and the variety of subject matter treated can be attributed in large part to the immediacy and intimacy of clay as a medium".6 The soft, tactile surface of a newly made pot evokes an almost irresistible urge to add marks to it in the form of incised circles or bands of coloured slip or pigment, especially if the pot is on a wheel, whether it be the slow wheel often used by ancient potters as a convenient way of revolving the work or on the more recent potter's wheel.
In Egypt, good hard-fired earthenware has been reported from around 3100BC, decorated with white slip on a red body. This indicates a ware that may be less porous than other earthenwares but again there is no indication of a firing temperature. The decoration ranged from stylized animals and scenes to plant life and figures. Up to 3000BC in the Aegean and Greece handmade red earthenware with incised decoration, was sometimes burnished. The shapes, some with long spouts, had their surfaces treated with terra sigillata and the decoration was of simple geometric patterns.
There are many references to the influence of metal objects on pottery shapes both from Europe and from China but Cox7 speculates that in all probability the first metal shapes were influenced by those of pottery. It seems logical that our ancestors would have learned how to shape the more easily worked clay before the much more difficult metal. Digs of the Middle Bronze age (2000-1580BC) have revealed pots of a grey body with the plant and marine motifs painted in a very stylized manner. These pots appear to have been made on a 'fast wheel', that is a potter's wheel revolving in such a manner as to leave the hands free. This was in Crete and is thefirst referenc e to a true potter's wheel. Like pottery itself there is no factual evidence of where thefirst wheel appeared. It is generally assumed that it came into being in various places and that the idea sprung from the fact that the hand building of pots was facilitated by placing the ware on some sort of stone or board so that it could be revolved slowly by hand as the pot grew. This saved the
6Foley, in Clark, p. 119. 7Cox, p. 104. 7 potter the trouble of walking around the pot. Its evolution only needed the potter to balance the flat stone or board on a point so that it would be pulled around by hand sufficiently fast to allow a true 'throwing' motion. The simplest motive power was of course the hand, either the potter's own or that of a helper. In Japan even today the potter's wheel is turned with a stick inserted in holes in the rim of the wheel head. When speed is attained the stick is put down and the clay manipulated. When the speed slows the stick is inserted again and the speed increased. A great improvement occurred when the wheel head was attached to a shaft with a flywheel that could be kicked around by the potter's foot so as to maintain a constant speed and leave the hands totally free. Over a long time the only real change has been the provision of external power to drive the wheel, human power, water power, motor power and electrical power.
During the Late Bronze Age (1580-1100BC) the emphasis in Grecian vessels was again on stiff shapes based on metal models, with decoration adapted from wall painting. Later, in the Early Iron Age (1100-725BC), the development of the large amphorae and kraters reached its peak. These were for wine use and the shape was that of a swelling bulbous body with an excessively narrowed foot, and at the neck was a pair of decorative handles, too small to be useful. For more than two thousand years there has been an almost universal adulation of Greek pottery. Walker proclaimed that Greek pottery was "the greatest art of the ceramist ever known on this earth".8 Certainly the painting was excellent and deserves praise but some potters feel uneasy about the shapes. Cox devoted a page or so to an analytical criticism setting out the weaknesses of the design of Greek pots. These included weak and badly placed useless handles, spouts that were too wide to pour properly, excessively narrow bases necessitating the addition of "flat attached bases which spoil the rhythm of the curves",9 and are easily broken, horizontal handles indicating two-handed drinking and so on. With regard to the painting, whether it is "black figure" or "red figure", he is lavish in his praise. It is interesting to note that none of the Greek potters signed their work as makers but many of the painters did, including Cleitias, Ergatimas, Execias, Amases and Nicosthenes. During the Classic period to 330BC and the Hellenestic, from 330 to 30BC, a decline in the quality of painting led to the production of plain blackwares which were, according to Cox, "undistinguished"10.
Of the pottery of Italy in the period 1200BC to about 2100AD Cox writes, "If Greece started the trend towards the worst of bad taste, Italy carried it on to its
8Cox, p. 51, 9Cox, p. 51. 10Cox. p. 54. ultimate conclusion".11 In Villanova pottery was a crude ware with crude decoration. The Etruscans showed what was possible with a gigantic pottery warrior, about eight feet high, made in about 500BC. However, their main pottery business was copying little Tanagra figures and making objects, "of unfelt mythological subjects, girls lounging in ornate grandeur among flowers, ribbons, pet animals and other sloppy ideas of design".12 Perfume bottles were made of whole busts of women surrounded by scarves and swirls. Hannover wrote of them, "The objects are considered to be among the greatest treasures of the Museums that possess them", (the Louvre, the British Museum and the Berlin Museum), but he adds, "although they are in every way more curious than beautiful."13
EASTERN HISTORY
China-from Shang to Ming On the other side of the world in China at An-Yang in Honan province and in Kansu province Andersson14 found large wheel-thrown pots of highfired brown clay. These were at first claimed to be from the period 3200BC to 2900BC but later Liang Ssu-Yung estimated that they were probably made between 2500 and 2000BC. Betts has dated some hard white pottery, also at An-Yang, at 1800BC.15 These claims are significant in comparing Eastern and Western cultures. Whereas all the excavations in Europe and the Middle East have revealed earthenware of various types the early An-Yang finds have been described as "hard baked" ware and "hard white pottery", indicating that at that time China had the means, the clay and the kilns to produce wares assumed to be stoneware.
In China, in the history of the pre-Han there were four periods-the Hsia, Shang, Chou and Ch'in. The Hsia, about 2200BC to 1700BC, is regarded as legendary. A good deal is known about both the Shang (1766 - 1122BC) and the Chou (1122 - 249BC). The Chou period occupied the longest period of China's history. The Ch'in (249 - 207BC) then took over and though it dominated for a very short period, was of great importance. The Ch'in Emperor unified China for the first time, the Great Wall was completed and a system of weights and measures introduced. This was also a significant period from a ceramics history point of view. It was customary to bury high-ranking persons with all their possessions, nCox, p. 65. 12Cox, p. 67. 13Cox, p. 71. 14Cox, p. 20. 15Cox, p. 21. 9 including living wives, concubines, servants and animals. After Confucius stopped this the custom was still followed but instead of live burials pottery models of everyone and everything were substituted. Much of the knowledge of those times and customs has become available to us through excavations of burial sites. These were found when railways were built and earthworks and cuttings revealed some of the tombs. The discovery and excavations near Xi'an which brought to light the now famous "Entombed Warriors" was a most exciting event. Outside Xi'an some peasants drilling for a well near a large mound accidently found the site of what is now known to be where the warriors and horses were buried to protect the tomb of the Emperor Ch'in. I was in China in 1978 with a party of Australian potters and at that time the early excavations had been stopped after the recovery of about eight warriors and three horses. This was to allow a large building to be erected to completely cover the site. The policy of the Chinese seems to be to build a museum on the actual site instead of transferring artefacts to some existing museum.16 All that existed on the site in 1978 was a small bamboo building in which I saw two of the warriors and one of the horses, which at that time tourists were able to touch. It was estimated that some eight thousand warriors were buried there and I understand that now the excavation is complete the ranks of warriors stand in order in their original formations and the damaged figures have been repaired. The warriors are larger than life size and are modelled in great detail with heads thought to be accurate portraits of actual soldiers. It is thought that each figure may have been modelled in a dark grey clay then a small kiln built around it for firing in situ, thereby overcoming the difficulties of handling such large pieces. Near Xi'an there is also an excavated stone age village dating back 6000 years. It too is a museum on the actual site and contains about six potter's kilns which could still befired today .
The Han dynasty, from 200BC to 220AD, made contact with the West. The Chinese established an embassy on the Persian Gulf, trade in iron and silk was established with the Romans and Buddhism was introduced from India. The pottery was strong in design and making. It was fired to a high temperature, some of it of a porcelaneous nature in that it contained kaolin. Some of it was unglazed while a great deal of it was glazed with a simple alkaline glaze which was transparent and the colours varied from yellows to browns to copper greens. According to Cox the glaze was introduced from the West through trade. He points out that Roman jars were traded into China and they exhibit a similar glaze. Cox maintains that this was the first glaze used in China.17 There was a
^The immense building was constructed of Lysaght Steel from Wollongong. 17Cox, p. 75. 10 development of shapes from the early Shang and Chou pots and the number of articles made was greatly increased. Large numbers of wine jars survive perhaps because they were buried with the dead. Other pots were incense burners, water droppers for use in writing and painting, storage jars and models of buildings, farm yards, horses and other animals. Cox shows photographs of the first porcelaneous pottery consisting of vases of a grey ware with yellowish or greenish glaze.
Personally I am uneasy with Cox's ready acceptance that the Han pots were glazed with the "simple alkaline glaze"18 from the West. The fact that the pots were fired high enough in the kiln to become stoneware and porcelain indicates to me that the glaze could be a primitive stoneware type. The Chinese kilns were fired with wood and the insides of the kiln become coated with a glaze formed as fly ash settles on the walls and melts at stoneware temperatures. This type of glaze is typically yellowish or brown or green. Unglazed pots are certainly affected in exactly the same way. The Han pots I saw in China had this glaze. It was so typical of wood firing that I never thought of any other explanation.
Modern potters use this ash glazing method, especially in large single chamber kilns called by the Japanese anagama or 'cave kilns'. These are fired for many days, allowing the ash deposits to build up. The effect can also be achieved on pots fired in any kiln without longfiring b y sprinkling wood ash on the pot while it is still wet. Perhaps the simplest of all stoneware glazes consists of 50% each of wood ash and clay. Later, in T'ang times many of the famous horses, camels and other animals were glazed with soft glazes, not alkaline, but those based on lead.
Nigel Wood19 in his book Oriental Glazes maintains that early Chinese glazes were in fact the ash glazes consisting of either equal parts wood ash and clay or with some variation in the proportions. I have already noted that Chinese kilns were fired with wood. The wood was pine and pine ash is much more fusible than that of most other woods. One of the most useful oxides used as a glaze flux is lime (CaO) and wood ash is high in lime. A glaze consists of a flux, alumina and silica. Clay is composed of alumina, silica and water so mixtures of ash and clay have the right ingredients for a glaze though not necessarily in the ideal proportions. These glazes usually run if oveifired due to a lack of silica. Wood is of the opinion that most early Chinese glazes were made of mixtures of clay and lime. The clays were highly silicious and the lime was used either as crushed
18Cox, p. 157. 19Nigel Wood. Oriental Glazes. Pitman, London, 1978. 11 limestone or slaked lime. Wood shows a photograph of a pot made between 100BC and 100AD which illustrates, even in black and white, the thick flowing glaze in which the flow has been controlled by deep parallel grooves and ridges. The pot is made from a clayrich in iron and impurities and Wood suggests that the glaze recipe would have been the body clay and lime in about 2:1 proportions. Some of these early pots have glazes that are quite dull and almost matt in appearance, typical of glazes that are too high in calcium. When in China I visited several Tang dynasty kiln sites and the shards of the high iron glazed ware, the blacks and browns, which lay around were usually typical of this high lime mattness. The large amount of lime, too much to enter into a proper glass melt, allows the excess to crystalise out in cooling.20
The 'Six Dynasties' and the Sue periods lasted from 220AD to 617AD. There was a development of the animal models and in particular the horse which was now well-modelled and vigorous. Human figures representing merchants, musicians, dancers and servants appeared in great numbers. The pots continued the Han shapes but often became over-decorated with applied ornament.
The T'ang period from 618 AD to 906AD was one of great achievement in all fields of art. It was a period of great painting, the development of wood block printing and the writing and poetry were unsurpassed. Pottery techniques also advanced, the pots being lighter and thinner and very high fired. At last Cox mentions shards of porcelain with a feldspathic glazefired at high temperatures at a site dated in the 9th Century.21 The glazes were white, celadon green, brown, black matt and some with bluish tinges. There is also mention of a "tea dust" glaze which is a typical high-fired stoneware glaze with high lime content which crystallizes out on cooling to form yellow green pyroxene crystals. The Chinese tea (and Japanese tea) is green, hence the name of the glaze. Again this is evidence of the use of a very high fired glaze. During the T'ang times there appeared also what Walter Hochstadter22 described as the first of the "transmutation" glazes, the Juns. The Jun colour is a blue that forms with certain material combinations and the right firing, the colour derived from the optical effect of suspended particles rather than by a pigment or oxide. Potters call it an opalescent glaze perhaps because of the
2uWood draws attention to the well-known eutectic of lime, alumina and silica having the formula of CaO 23.5, AI2O314.75 and Si02 62.0. A recipe expressed in parts by weight would be kaolin 30.4, lime (calcite or whiting) 33.6 and quartz 36. Many potters use what is called the "equal parts" recipe i.e. whiting 1, clay 1, quartz 1. The method of converting the formula to a recipe is dealt with later. The eutectic noted above is supposed to melt at 1170° C but is probably better at 1200° C. 21Cox, p. 113. 22Cox. p. 174. 3 0009 03155620 7 12 similarity to real opals although the opalescence bears no chemical similarity to the gemstone. The pots of the T'ang continued to develop. Already strong shapes became even more elegant. The famous T'ang horses were more finely modelled and there were more human figures of both men, women and warriors. Vases, wine jars, ewers and bowls were now glazed in the newly-developed high temperature glazes. The Chinese appreciated the beauty of the pottery and Cox includes a verse by the poet Hsu Yen which was written about some cups made for the Emperor:
Like bright moons, cunningly carved and dyed with spring water; Like curling disks of thinnest ice,filled with green clouds; Like ancient moss—eaten bronze mirror, lying upon the mat; Like tender lotus leaves, full ofdewdrops, floating on the riverside!73
Despite wars, internal conflict and conquest by the Tartars and Mongols, the pottery produced during the reign of the Song Dynasty (960AD-1280AD) has been universally acclaimed as the finest ever. In my opinion the continuous development from the earliest times in glazes reached a peak that has never again been equalled. Some of the shapes are overdecorated by modern standards but for potters the glazes command the highest admiration. The greens of the Lung'Chuan celadons are rich and unctuous. The Chuns and the Copper Reds were well-developed glazes and the methods of working and firing of kilns were ideal for the results. The Song potters used the materials available in the most direct way to achieve the results most suited to them, working in a very direct way. Western potters today do not have the benefit of the centuries of continuous development of the Chinese but many have adopted in some form the ideas of Eastern ceramics.
Cox simply states that the glazes in the late T'ang time and in the Song were feldspathic. In contrast Wood24 states categorically that Chinese glazes were never based on feldspar, which is a modern European tradition. He attributes the success of the Song glazes to the development from clay-lime glazes to what he calls lime-alkali glazes. It is a well-known fact that while glazes can be made with only one flux in the formula much better glazes are achieved with the introduction or two or more fluxes. The Song glazes have been analysed and show between four and seven percent of potash and soda. This is what has caused Cox to call them feldspathic glazes on the assumption that these oxides must come from
23Cox, p. 124. 24Wood, p. 56. 13 feldspar. However, Wood concludes that the potash found in the analysis in fact comes from its inclusion in Chinese materials and in the potash mica called sericite. As the glazes were still mixtures of the body clays and other materials the mica would be a natural and accidental inclusion. Chemical analysis can indicate the presence of potash but cannot show from what material it is derived. The fine mica would have made the clay much more plastic and ideal for throwing. The large amount of clay in the glazes made them ideal for application to the leather hard pots before firing, a technique sometimes called raw glazing which was always practiced by the Chinese.25 The technique eliminates a first or biscuit firing and is also known as 'once firing' or 'single fire'. It is strange that these beautiful pots were made at a time when the country was far from peaceful, there was much internal conflict and intrigue and the threat from the Tartars became a reality. The Song rulers were forced to cede territory and move South. Soon after, the Mongols and Jenghiz Khan invaded, the conquest became final in 1280AD with the last of the Song Emperors throwing himself in the sea in despair and Kublai Khan became emperor of the whole of China. It is probable that for a time these wars cut off the foreign influences from the West which had been growing since the Han period and may have therefore compelled Chinese art to fully draw upon its own Chinese resources.
It is not my purpose to rewrite the entire output of the Song potters. Accepting the views that the Song were supreme potters I can only briefly note some of the directions they followed especially with glazes. The early Ying Ching porcelain was made of hard white vitreous body and the pale blue glazes were coloured by very small additions of cobalt. The imperial wares known as Kuan Yao were often made of dark brown clay with glaze colours of deep green, 'moon white', pale blue and bluish or greenish colours tinged with red. Crazing in the glaze was beginning to be controlled into both 'crabs claw', that is large crackle and 'fish roe', which is very small crackle. From our Western point of view crazing is one of the faults of glazes. It appears after firing as a maze of cracks in the glaze. It results from the fact that the glaze and the clay body have had different coefficients of expansion. While the glaze is fluid, at the top firing temperature, it fits onto the clay with no problems but as the ware cools and the glaze freezes into a hard glass it has greater shrinkage than the clay and it cracks under the strain. The problem is solvable by modifying either the glaze recipe or the clay body. Crazing is more of a problem with porous earthenware pots as the crazed glaze allowed moisture to seep through but is not a practical problem with stoneware and porcelain which by
25During the Industrial Revolution with the division of labour in factories biscuitfiring was introduced. 14 definition have vitrified bodies. As stated above the crazing can be in a fine pattern or a large one. The Chinese with their undoubted technical ability found ways to overcome this "fault" but also realised its potential as a decorative device in its own right. The change of description from "crazing" to "crackle" helps too. The crackle can be evident when the pots come from the kiln or it may continue to develop literally for years. Its decorative effects are often augmented by placing the pot in a dye bath or by applying ink, neither of which are inherently pottery techniques. The colouring of the crackle occurs more naturally with the pot's use which causes impurities to settle in the craze pattern.
The glazes we call celadons of the Lung-Ch'uan kilns (and others) deserve special mention as they present a very good example of the ability of the Song potters to maximise the inherent possibilities of their materials. The kilns were probably started in the 9th Century and during the Song period these green glazes were continually improved. Anecdotally it is reported that the green colour of the ware was later called "celadon" after the clothing of that colour worn by a shepherd in a play in 17th Century France The name is now used world wide. The colour is achieved by a small amount of iron oxide in the glaze and by the manipulation of the fire in the kiln. Many clear or transparent glazes can be coloured by an addition of red iron oxide (Fe203). Fired in an oxidized atmosphere in the kiln the addition of about 1 % Fe203 will fire to a pale amber in some glazes and larger amounts make the glaze darker until with 10% and even more the colour will be a brown of some kind. Oxidation in the kiln exists when there is sufficient air admitted to burn the fuel fully and efficiently and the oxide remains unchanged as Fe203. However with approximately 1% Fe203 the colour can be changed to the green of celadon by a reduced atmosphere, that is, where the air supply is reduced to make an inefficient flame starved of oxygen. This flame will take oxygen from any source and in this case attacks the iron oxide and removes some of the oxygen thereby changing the Fe203 to FeO and with it the colour from amber to green. The Lung-Ch'uan celadons not only have the colour but have a soft, thick, tactile appearance called by some 'unctuous'. Mere green is not necessarily celadon in the view of many potters and collectors. The green can vary from a bluish green ("blue like the sky after rain")26 through greyish greens to olives and yellowish green. For some reason the more blue the celadons are the better they are considered. Most modern celadons are achieved by the addition of iron oxide to a transparent glaze but the Song potters used glaze materials that had in them small amounts of iron oxide and they learned how to exploit this in the most magnificent and appropriate way. Even a transparent glaze fired in reduction on a dark clay
26Cox, p. 141. 15 body will dissolve enough body iron to become green. The Song potters worked with the celadon glaze until it fulfilled their ambition to make it imitate jade. It was described at the time as "jade green". Much of the decoration was incised, moulded or modelled before glazing and where the glaze ran into the deeper marks the colour was darker and richer.
The Jun glazes with the addition of small amounts of copper oxide became more colourful and descriptions from that time list such variations as "rose purple", "cherry-apple red", "aubergine purple", "plum-bloom green" and "sky blue". Brown glazes coloured by large amounts of iron oxide continued to be used. These we now know generally as 'temmoku' which is the Japanese word for them. These high iron glazes can be black, brown, purplish brown, have flow patterns called 'hares' fur or segregations of iron called 'oil spots'. This dark brown glaze was also used in a most decorative way on the wares known as Tz'u Chou where the glaze was applied to the unfired body and then the glaze was cut back to the clay in vigorous patterns. Pots of this type are some of the most beautiful of all Chinese wares.
The Song potters also produced a ware called Ting which featured a reserved cream, almost matt glaze. The cream colour was achieved because of a small amount of iron oxide in the glaze probably as an impurity in the clay used and the wares would have been fired in an oxidizing atmosphere. A reducing atmosphere would have turned the glaze towards the celadon colour. The Ting ware was interesting too in that many of the bowls were fired upside down and the unglazed edge was later covered with a metal rim.
The Ming period, another one of the great periods of Chinese art, ran from 1368— 1644AD. The Yuan era connected the Song to the Ming in which the art traditions were continued. There were important happenings in that the trade routes in the Middle East were made safe and there was considerable interchange between the Arabs and the Mongols.
The purity of the Song pottery is regarded as unequalled and the Ming in many ways continued the fineness of the wares and continued to improve the quality of the porcelain body which became extremely hard, pure white, translucent and completely vitreous. It should be noted that porcelain is only translucent in certain thicknesses. The Chinese paid no particular attention to translucence realising that a thick section of porcelain was still porcelain despite the lack of translucence. Ivan McMeekin27 once told me that the Chinese had no word for translucence in
2^Ivan McMeekin, private conversation. 16 any case. Crackle glazes were perfected in Ming times and coloured glazes were popular. Cox states that the white glaze was coloured with manganese for violet, copper for turquoise, green and red, iron for "dead leaf brown and antimony for yellow.28 I disagree with Cox about the yellow. The yellow resulting from the use of antimony does not withstand the high fire—what the French call the "grande feu" of 1300°C and above—as is usually indicated on the product by the manufacturer. Potters making earthenware can prepare the yellow stain by mixing and roasting antimony, white lead and tin oxide then grinding and washing the resulting mixture. The colour is what the paint manufacturers call Naples Yellow. The stain is very good at low temperature only. I contend that the Ming yellow is fired on the porcelain at a lower temperature in a subsequent firing. I always tried to make yellow glazes in my stoneware pottery, remembering the two beautiful yellow vases in the Kent Collection in the National Gallery of Victoria, but I did not succeed. My yellows based on iron oxide were always green or olive because I have always fired in reduction, whereas the "Old Seto Yellows" of Japan are actually celadons fired in oxidation. When I was in China I made constant enquiries about the composition of the yellow pots I saw but usually received no real answer because the guides and the museum attendants did not have the necessary technical background. While in Peking (Beijing) our group naturally visited the Imperial Palace (The Forbidden City) and were received by the Director of the Ceramics Collection. In his office we drank Chinese tea from yellow bowls decorated with green dragons - Imperial wares from the 17th Century. In one of the large pavillions housing the ceramics was an exquisite small porcelain bowl, pure white inside and pure yellow outside. I put my question to the director who examined the information about the bowl and told me that it was a Ming bowl made in Peking and then sent to another city for the outside to be glazed with an antimony yellow! Chemists and potters have solved the problem of a high fire yellow stain but it has no antimony in it but is made of vanadium and tin and it is a very modern stain. Stain manufacturers still make the antimony stain but warn that it is only useful up to a little over 1100°C.
The copper reds were developed, under-glaze colours perfected and enamels for on glaze (that isfired o n to the finished pot at low temperatures) became popular. Gradually the wares became more ornate and towards the latter part of the Ming they took on the over-decorated nature associated with the later so-called 'decadent' periods. Cox quotes an amusing anecdote regarding the popular blue and white jars popular in the West because of their primus blossom design and the fact that they contained ginger. A collector said that by simply removing the
28Cox, p. 132. 17 ginger the "jar became a Ming pot in an instant!"29 The Ming saw the blue and white wares reach an almost perfect state. Their popularity has continued until the present not only in China but in most factories all over the world.
Ming wares were many and varied and were produced in vast quantities for the Imperial Household. Cox mentions that in the year 1554 the Imperial order for one kiln included 265,350 bowls with dragons in blue; 30,500 plates; 6,900 bowls and so on.30 A large part of the Ming wares collected and recorded are in fact either Imperial wares or made for the rich and noble. However there were also millions of pots made by village potteries for the use of the common people and it is possible in China to find large hills composed almost entirely of Ming shards and kiln wasters. Near Ching te Chen I acquired two broken bowls of the 14th Century called 'Village Ming' which have free blue brushwork on a translucent white glaze.
Japan. The earliest pottery in Japan is called Jomon. The name is said to refer to the decoration which was made by impressing ropes or cords into the wet clay. The ware was heavy and clumsy and unglazed but showed the ability to organise complex decoration. Jomon wares were made from about 1500BC until about 200BC.
The Jomon was replaced by Yayoi, a reddish-brown pottery, very fine, and whereas the Jomon pots were hand built the Yayoi were mostly made on a pottery wheel. Of particular interest were the clay figures called Haniwa made to be placed in tombs. Haniwa sculptures included animals, houses and boats and have contributed to our knowledge of the social life of the time.
A new type earthenware replaced the Yayoi. It was still unglazed but it was very hard indicating superior kiln design and higher temperatures. Tadanari Mitsuoka31 in his book Ceramic Art of Japan states that this superior knowledge came from the continent. There were two types of kiln, anagama and noborigama. The anagama (cave or cellar kiln) consisted of a very large chamber for the ware with a very efficient fire box at the front. The kiln was usually built on a slope to aid draught. The noborigama or sloped kiln was a development of the single chamber kiln in that the shape evolved to become a series of chambers interconnected up the
29Cox, p. 160. 30Cox, p. 182. 31Tandanari Mitsuoka. Ceramic Art of Japan. Japan Tourist Bureau, Tokyo, 1953. 18 slope,fired initially with afire box at the bottom. When the first chamber reached temperature the kiln was stoked with wood through a series of holes in the side of the kiln. This side stoking was continued at each succeeding chamber up the hill. It was an efficient way of firing. Such kilns still exist in China; Korea and Japan and some artist potters in Australia have also built similar kilns. The kilns were inu-oduced into Japan by way of South Korea. The pottery was called Sue and the kilns were introduced at around the end of the Han dynasty in China. The Sue tradition was widespread and lasted almost to the 12th Century.
I was fortunate to have seen and handled pots in the collection of Toyo Kaneshige at this house in Bizen in the early sixties. Kaneshige's collection included Jomon, Yayoi and Sue wares. Mitsuoka maintains that the Sue tradition lived on in the famous Bizen wares, the Shigaraki wares, the Tokoname wares and the Tamba wares. These kilns, and others, yielded unglazed wares dependent on the accumulation of ash melting on the pots during firing for decoration. They are still operating and are popular places for potters to visit from all over the world.
From the time of the Sue wares almost to the Meiji period there is no doubt that art and ceramics in Japan were dominated by all things Chinese though there is general agreement that these Chinese influences were modified by Japanese tastes and preferences. Peter Swann32 in his Art of China, Korea and Japan makes a list of the various periods in Japanese art from the Sue and Great Tombs period (to about 500AD) including in historical order Asuka, Nara, Komin, Heian, Kamakura, Muromachi, Edo and Meiji. In all of these can be traced the modifying Japanese taste upon Chinese originals. Great pottery centres arose at Seto, Karatsu, Kyoto and Satsuma which made stoneware products in great quantity, still based on Chinese influences. The glaze known as Shino, made of a special kind of feldspar, was used widely. Its near companion, Oribe ware with its copper green and white glazes, was regarded as being influenced by the Ming three-coloured wares.
The main change in Japanese pottery resulted from the introduction of porcelain. General Toyotomi Hideyoshi invaded Korea in 1592 and again in 1597 and upon his return brought a group of Korean potters, probably prisoners, back to Japan. Their leader was Ri Sanpei and they settled on the island of Kyushu. Kyushu is the closest Japanese island to Korea and all the attacks on Korea were launched from there. The Koreans set up kilns and discovered a satisfactoiy porcelain clay called Amakusa stone at Izumiyama near Arita in about 1616 and so the Japanese
32Peter Swann. Art of China, Korea and Japan. Thames & Hudson, London, 1963. 19 porcelain industry was born. The city of Arita is still a very large porcelain producer but the wares are generally known as Imari wares, named after the port from which they were exported. Arita produced fine porcelain in the blue and white tradition and later wares decorated with coloured enamels. The works of the Kakiemon family were highly prized for the delicate brushwork on the milkwhite glaze. The family continues to live there to this day. Nabeshirna ware was another veiy highly regarded because of the excellence of the enamelled porcelain. It was never exported as it was made only for a noble family. Porcelain factories rapidly spread to many other parts of Japan.
Not many individuals are mentioned in the early days of porcelain production but the Japanese revere the work of Nonomura-Seiemon known as Ninsei. He was a famous artist who set up a kiln in Kyoto and produced wares for the tea ceremony, and he was succeeded by a pupil, Ogata Kenzan, whose work as described by Tadamari Mitsuoka, "consists in the freedom, gracefulness, and gentleness of expression which is a direct reflection of Japanese taste"33 His work was widely copied by several factories.34
After the Meiji restoration in 1868 Japan went through a period of rejecting everything Japanese in an attempt to become a 'modern' nation but later turned back to her own art. The influence of the Japanese crafts on artists all over the world has been profound.
Korea Korea, a peninsular connected to Manchuria, was naturally and easily influenced by Chinese pottery, but invariably distinctly Korean characteristics appeared and Korea made a definite contribution in allfields of art including ceramics". The Korean potters evolved a decorative technique called hakeme which involved a swift brushing of white slip onto a pot, leaving the brush marks. The pot was then glazed with a transparent glaze. Yanagi notes that the brushes could be made of hair, hemp,rice stra w or grass. The technique is still much used on the country wares in rural Japan and I have seen the great Hamada collect a handful of grass outside the studio to create the hakeme effect. The word "hakeme" actually means brushmark. The beauty of hakeme is said to depend on an almost unconscious application of the brush with a swift direct sweep. It is thought that originally the white slip was used (and still is) to cover a dark or rough clay and potters
^Mitsuoka, p. 57. 34It is interesting too that Bernard Leach learned his pottery from a potter called Ogata Kenzan the sixth so Leach could have called himself "Kenzan die Sevendi". 20 discovered the beauty of this hakeme technique. The superb painted decoration in iron pigment continued through the Yi period. Early in 1994 in New York I was fortunate to see a comprehensive exhibition of Korean pottery at the Metropolitan Museum of Art. The pots were mainly the celadons, the special grey-green already mentioned and the jars of the Yi period decorated with iron oxide brushwork. Though Korean pottery is noteworthy most of the modern pots appear to be made in factories. Only near the ancient capital did I find a small pottery with a couple of small climbing kilns producing the unglazed wares reminiscent of the Silla period35 and recently I have noted articles referring to artist potters setting up studios in various locations.
^^The pottery was called the Silla Pottery 21
European Lustre Ware. From Roman times to 18th Century Europe all pottery was earthenware and Cox almost dismisses it as being unimportant except for a couple of very interesting developments in glaze techniques. The first of these is lustre. The other is tin glazing which will be dealt with later.
Lustre is an on-glaze technique which ionises on an already fired glaze a very thin layer of metal that imparts an iridescence to the colour. It was perfected in Islamic counuies and in 712AD was introduced to Spain when Musa b. Nosair the Arab conquered Spain. It flourished as a dominant raw glaze technique and the Hispano-Moresque wares constitute one of the great pottery arts. The glaze was used to best advantage on the large platters decorated with simplified animal designs and coats of arms. Lustre glazes can be gold, silver, blue, red or yellow. Sanders in his book Glazes for Special Effects^6 noted that the glazes may have originally been used as an inexpensive substitute for gold and silver wares. The lustre of the Middle eastern potters and (subsequently) the Spanish, was produced by painting the metallic pigments in the form of a paste on to a glazed surface and then refiring. Sanders37 states that the ware should be of soft earthenware and the glaze should be a lead/soda type. He also notes that high fired wares can be lustred as well. The lustre pigments are composed of earthy materials such as ochre, burnt umber and burnt siena all of which are partly iron and manganese oxides. Silver carbonate is added to the earth paste and it can give yellow, gold and bronze colours. Copper carbonate results in red and ruby colours as well as a metallic copper. The ware isfired in a kiln, often a special one, to the very low o temperature of cone 022 which corresponds to 605 C. With the kiln at dull red heat smoke must be created in the chamber. This is done by dropping combustible materials into the kiln. These can be moth balls, sawdust, oil, rags or wood soaked in oil. When cool the ware is washed to remove the sooty paste to reveal the metallic colour.
It should be noted that the above description applies to the traditional reduced pigment lustre. Modern potters produce the effect much more easily because commercial lustres are produced as self-reducing liquids which are painted or sprayed on to the ware and fired to cone 020 (650°C) or 017(730°C) in an oxidizing atmosphere.
36Herbert H Sanders. Glazes for Special Effects. Watson-Guptil, NY, 1974. ^Sanders 22
The early lustre wares in Spain were Islamic in every way. The painting and decoration had been transported with the Moors and featured arabesques, 'tree of life' palm trees and with Islamic calligraphic inscriptions. Cox notes that sometimes Spanish inscriptions were misspelt by Moorish workers and those in Maghribi calligraphy were misspelt by Christian workers. The Moors were driven out in 1610 and thereafter Gothic foliage, flowers and 'chain mail' patterns in great detail became popular.
Lustre appeared in Italian ceramics in 1497 where it was made at Deruta, still a pottery centre, north of Rome towards Florence. It is not known why lustre appeared at this centre. Hobson and Burton agreed that "the earlier examples are hardly distinguishable from Spanish ware, and to the last the ware remained technically like earlier ware, though with perfectly Italian decorative treatment".38
^Hobson & Burton, in Cox, p. 368. 23
European Tin Glaze. In Europe tin glazing was developed, used for a period, lost popularity, and was then rediscovered and it appears on some of the very earliest pottery. It was probably associated with the earliest alkaline glazes and later with glazes based on lead, and again there is no information on the events leading to it. To make a transparent glaze for earthenware the potter needs to melt silica which is in nature a glass former. To get silica to melt it must be combined with a flux. In early times alkali fluxes of soda and potash were used and some time later lead oxide became the most common flux. Lead oxide is one of the most vigorous of the fluxes and makes possible excellent transparent glazes often coloured with metal oxides of copper for green, cobalt for blue, iron for yellow and brown.
It was found that the addition of up to ten percent of tin oxide made the glaze opaque and white and from the earliest times this 'tin' glaze was used to either cover clay that was coarse or dark or to provide a white surface upon which to paint. Tin has always been very expensive and therefore in Italy its early use was to cover only a portion of the pot. It proved to be a perfect surface upon which to paint decoration in the low fired 'enamel' colours. Later, when Chinese blue and white porcelain was imported into Europe, the potters used the tin glaze and cobalt in an attempt to copy it. The great pottery centre of Faenza in north east Italy was started in the middle of the 16th Century and it gave its name to decorated, tin glazed wares which are now universally known as faience. An alternate term, majolica, is sometimes used, named after the island of Majorca. Technically the Dutch Delftware is exactly the same although it was a deliberate attempt to reproduce the Chinese blue and white wares. This earthenware is nothing like Chinese porcelain other than superficially being a blue and white ware. It was not until the early 18th Century that European porcelain was made.
A good deal of our early knowledge about the production of faience in Italy comes from a book written by a potter, Cipriano Piccolpaso.39 In the late 15th century he wrote exhaustively about the methods, clays, glazes, pigments, kilns and the firing used in Italy. He tells us the firing should not be done during the moon's wane because the pots would then lack brightness! The pots of this period ranged widely to include jugs, vases, platters and alberelli or apothecary jars with concave sides. Italian tin glazed wares often combined the excessive use of colour with decoration which was storytelling and pictorial to the point where there was little room for appreciation of the beauty of the pot itself.
39Cox, p. 356. The coloured enamel tin glaze pottery spread to France and Germany where it was continued in more or less the same style as in Italy with ornately shaped ewers and storytelling decoration. I have written earlier that all European pottery from Roman times until the discoveiy of porcelain in the 18th Century was earthenware, that is, low fired porous ware. The exception was in Germany prior to the 16th and early 17th centuries where true stoneware was made. Stoneware is produced by firing the clay to sufficient temperature to cause the clay particles to fuse or vitrify so that the ware is so dense that it can hold water without a glaze. The stonewares were based on clays found along the Rhine and its manufacture was confined to a relatively small area including the towns of Hohr-Grenzhausen, Sieburg and Cologne. The clays varied in colour from near white to dark brown and the wares were extensively modelled upon with coats of arms, the hunt, women and merchant's marks. The best known applied modelling is in the form of a bearded face on the neck and shoulders of a jug. Glaze in the conventional sense was not applied, but salt glazing was employed. When the kiln reaches high temperatures common salt is thrown into the kiln where the heat breaks it down into its components of sodium and chlorine. The chlorine gas exits through the flues while the soda vapour settles on the surface of the pots (and the kiln) where it combines with the silica in the clay to form a simple glaze. The glaze can be thickened by repeated applications of salt. This sort of glaze can show modelled decoration in a sympathic way where normal glazes may mask it. Later the pots were decorated with cobalt oxide painting and some wares even had coloured enamels applied. There is still an industry in Hohr-Grenzhausen though not on a large scale. I was there in 1977 and most of the massive old kilns are no longer fired and some have become display areas in museums. Cox40 writes that the 18th Century saw the end of handmade pottery in Europe and with it some of its human appeal.
40Cox, p. 418. 25
Chapter 3
INDUSTRIALISATION AND STUDIO POTTERY
In Europe in the 18th and 19th Centuries the Industrial Revolution changed the way goods were produced and the way people lived. The invention of machines to manufacture things that had formerly been made by hand and in small quantities not only changed the way people earned a living but made available to almost everyone standardized goods of every description. Starting with the textile industry, the spinning and weaving of wool and cotton, factories were built to supply almost every article used by the people. Mass production of great quantities of what we now call consumer goods meant that many articles came within the purchasing power of the average person. Large plants standardised materials, researched methods of production and organised the division of labour, all with the view to produce more and usually cheaper goods. This seemed to be a wonderful thing-more products of a good standard cheap enough for all to buy. But there was a reaction to the whole concept. Historically the goods and artifacts needed by the community had been supplied by local craftsworkers. The carpenter had made furniture, the blacksmith fire irons, hinges and horseshoes, spinning was a daily chore for the housewife and the weaver took the wool to produce cloth. The potter was often a village craftsperson who made the pots that the villagers wanted, such as milk pans, plant pots, storage jars and chamber pots. Potters mostly dug and prepared their own clay from local deposits in the manner of potters all through history. The pots were usually of red earthenware, fired in simple kilns capable only of attaining the temperature required for earthenware temperatures.
It was in China and the Far East that kiln technology had reached the stage where very high temperatures could be reached to enable stoneware and porcelain to be made, apart from the salt glazed pots made along the Rhine in Germany, as already noted. Outside China virtually all the pots made in the world at this time were red low-fired earthenware whether made by so-called primitive peoples or by potters in more sophisticated societies. In Europe many of the potter's wares were unglazed. If glazed at all the glaze was usually made from a raw lead ore called galena. The ore was simply ground to a powder and dusted on to the wet pot and when heated the lead in contact with the silica in the clay became a simple glaze. 26
More recent knowledge about the toxicity of lead glazes suggests that people would have suffered lead poisoning from glazes in contact with acids such as fruit juice and vinegar.
It has been said that Wedgwood, "created an industry and killed a craft". He led the indusuial reorganisation of ceramics in England creating factories which used mass production methods. The division of labour made cheaper pottery of a very high standard available to a broader public. His range of "Queens Ware" was very popular. Naturally other manufacturers soon followed his lead not only in England but in other parts of Europe as well. But his very success led to criticism of his quality and design and of the way that workers had become almost machine-like parts of production with the feeling that the input of the individual had been lost. Gone was the almost daily contact between the maker and the user. While the factory-made pots were of better technical quality a great number of people missed the personal touches that had characterised the handmade wares.
For instance, the texture resulting from the hammer of the smith was missing, as was the homely, uneven thread from the spinning wheel, the recognisable finger marks of the village potter and the simple but appropriate decoration used by the craftsperson. Even though factories often made articles in imitation of, or at least in the style of, the handmade the differences always showed. The anti-industrial feeling gradually grew into what is known as the Arts and Crafts Movement and the best known figure in the mid to late 19th Centuiy was William Morris. He set out to develop well-designed goods, furniture, wallpaper, textiles and ceramics. He set up companies to exploit the 'well-designed' concept. He was only partly successful but he laid the groundwork for what was to be a continuation of an arts and crafts concept, that there was still a place in society for artists and craftsworkers to produce articles that were well-designed while carrying the individuality that goes with a small workshop or a single worker. While the number of craftworkers continued to decline, Morris's concept was not lost, for what happened was that Arts and Craft Societies came into being and in various ways the members endeavoured to keep alive all manner of craft activities. Certainly until World War II most of the crafts were the province of the Arts and Craft Societies and of a very few individuals who continued to work as craftsworkers. In ceramics we have come to call these people Studio Potters or Artist Potters. It is not easy to define exactly what a studio or artist potter is because there are so many potters working in different ways who could claim the title. Some work together in groups sharing space and equipment, some actually work almost as a small factory, and others work alone. Many make pots in large numbers in what may be called a small factory attempting to supply the ordinary 27
needs of the community, as did the mediaeval potters, making mugs and casseroles by the hundreds marketing through markets and craft shops, while others set out to make individual pots in small series or 'one offs' and sell through their own studios and in exhibitions in galleries as painters and sculptors do. In Australia this concept was reflected in the aims of the Crafts Board in the seventies and eighties.
The Leach Contribution Before World War II there were some notable individual potters in France such as Chaplet, Games, Delaherche, Decoeur and Cazin and William Burton in England. However, it was the publication of Bernard Leach's book A Potter's Book41 in 1940 that sparked off a new emphasis on the individual as a potter and brought to the attention of Western craftspeople, especially potters, the art of Japan. While there had been much contact between China and Europe over the centuries with the large trade in Chinese porcelain, particularly the blue and white, and while there had been periods of great interest in all things Chinese when it was fashionable to decorate homes with Chinese artefacts, the 'Chinoiserie' period, and while the English factories had produced near copies of Chinese pots—the famous Willow Pattern is not Chinese but English—the effect on craftsworkers was minimal until A Potter's Book was published.
The same can be said about Japanese wares. After the middle of the nineteenth century when Japan opened up to the world following several centuries of complete isolation Japanese artefacts and pottery were freely available in Europe and European factories copied some Japanese styles. It is amusing to note that some English factories copied, with or without variations, the famous Japanese Imari Wares. Some of these variations were then copied by the Japanese factories and it became a three way copying style with some of the Chinese factories doing the same.
Leach claimed that the Song Potters produced pots that are among the best ever made. Their range of shapes was broad, the shapes were always suited to the function of the pot, decoration, when used, was also always suited to the pot and the glazes used were such that it is considered that they have never been bettered. The Celadons of Lung Ch'uan, the Kuan glazes, the Chuns and the Tz'u Chou readily spring to mind as amongst the supreme glazes of the Song period. The Chinese had at their disposal deposits of very suitable clays from which they
41 Leach. 28
developed stoneware and porcelain. The Song potters were making porcelain more than a thousand years before it was developed in Europe. The Song tradition pointed to the creation of pottery whichtteated available materials in a sympathetic way so that the clay and glaze were equally important to the shapes and concepts. But perhaps more important to the emerging potters was the Japanese aesthetic that Leach had promulgated, an aesthetic of actual living in which utility is the first principle of beauty. It is well known that Leach leamt his potteiy in Japan and his book was a manifestation of his belief that he was a bridge between the thinking of the way of life in the East, that is in Japan, and the West and his book in many ways sets out to bridge this wide gap. One of Leach's contemporaries in Japan was the famous Shoji Hamada and the works of Hamada and the other potters of his generation strongly influenced the thinking of Australian potters as they wrestled to fathom the Eastern wisdom, for example, of Hamada saying such things as, "good pots were made with ease, like a man walking down a mountain in a cool breeze".42 The country potteries of Japan had not been affected by the Industrial Revolution as such, so they had continued in their own traditional ways and it was men like Hamada and Kawai, one of his contemporaries, that added to this village pottery concept their own individualism and they became almost the model for the sorts of activities that some Australian potters followed.
It is difficult for Westerners to appreciate the general feeling for pots in Japan and the way in which they are revered. Japanese collectors pay vast amounts of money for the simple tea bowls and other wares associated with the tea ceremony. Such prices are never charged or paid in our Western society. No matter how much attention we pay to the Japanese it is difficult for Westerners to appreciate the sorts of standards they apply to the simple and often, to our minds, crude wares associated with the tea ceremony. But the tea ceremony, in many ways, drives the Zen aesthetic.
It is fair to say that Leach's book brought to the attention of Western craftspeople the methods and the aesthetics of the humble Japanese ceramic workers with their sympathetic use of materials, simple decoration and attention to function. Soetsu Yanagi said, "A beautiful artifact may be defined as one that reposes peacefully where it aspires to be."43 Leach drew a parallel between this Japanese tradition and that of the Korean potters and especially of the Chinese Song dynasty. Of course the Song artists did not just suddenly appear, making perfect pots. The Song followed several thousand years of continuous development of pottery in China. Early wares tended to use metal articles as patterns. Later pots became
42Hamada, in Clark p. 86. 43Yanagi in Clark, p. 119. 29 further expressions of what clay should do, to show the shapes more true to the fluid nature of clay and the methods used to attain these shapes. Chinese potters utilized the clays available in the best possible ways. The clay known today as China Clay or Kaolin demands high temperatures for its successful use and Chinese potters developed kilns capable of reaching the high temperature at which this clay fires to become stoneware and porcelain. In fact the very nature of the clay and its sympathetic use were the essential ingredients of porcelain making. The Chinese called this material Kaolin (from Gaolin the village where it was originally mined and still is) which literally means "High hill". Leach drew the attention of potters around the world to the Song tradition of the sympathetic treatment of clay and the use of superb glazes and to the excellence of the peasant wares of Korea and those of the Japanese village potters working in a traditional way. The Japanese called this village pottery movement the Mingei Movement but it included not only village potters but many of the great modem Japanese potters, such as Hamada and Kawai.
The Australian Scene After World War II the direction of artist or individual potters changed. Not only had Leach's book been a great influence but there appeared a new generation of people interested in careers in potteiy making unlike the hobby potters who had mainly constituted the Arts and Crafts Societies. After the War many ex- servicemen and women attended art schools as a part of government schemes like the Australian CRTS-the Commonwealth Reconstructions Training Scheme. Examples of this commitment can be found in the four potters in New South Wales who founded the Potters' Society of Australia, perhaps the earliest of the prestige potters' organisations in this country. A short note about each of them follows-
Mollie Douglas completed her diploma in Design, majoring in pottery, at East Sydney Technical college at about the time the War started. She had a studio at Turramurra where she produced pots based on the English tradition of slipware and lead glazes. She was also a teacher. fi
Peter Rushforth trained after the war in Melbourne where the chief instructor was Jack Knight and the emphasis there was on the earthenware tradition. Peter moved to Sydney to take up the position of head teacher of pottery at East Sydney Technical College in about 1950 when he was still making earthenware pots. 30
Ivan McMeekin took a completely different route from the conventional training that was available in Ausu-alia. Pre-War he had been an art student in painting and drawing. During his service in the Royal Australian Navy and later in the Merchant Marines he had visited China and seen Chinese pots at first hand and these struck a chord in him. He wanted to find out how they were made and tried to become involved in China itself. This was impossible in the post-war years with China in its confused state after twenty-odd years of the Japanese invasion, the political chaos of the Chang Ki Shek/Mao Tse Tung conflict and the coming to power in 1948 of the Chinese Communist Party. Having heard of Bernard Leach he went to England in the hope that he could train in Leach's St Ives workshop. Leach could not accommodate him and sent him off to Michael Cardew's workshop. Cardew was a well-known potter in the English earthenware tradition but had begun to make stoneware, influenced by Leach's Eastern ideas. McMeekin became a worker in Cardew's workshop and here he was able to acquire the techniques of stoneware production. When Cardew went off to Nigeria to introduce stoneware to the local potters McMeekin remained at Cardew's workshop running it successfully for several years. In the early 1950s he returned to Australia to take up the position of Potter at the famous Sturt Workshop which had been started by Winifred West. His brief there was to set up a pottery viable as an economic venture and also as a teaching facility. Ivan McMeekin brought to Australia a thorough knowledge of stoneware pottery.
My own introduction to pottery was different again. Pre-War I had been a part- time student at East Sydney Technical College in painting and drawing classes and while in England with the RAAFI managed to do quite a lot of spare time study at the Wolverhampton College of Art and at the Brighton School of Art. I was accepted as a full-time art student at East Sydney Technical College in 1947 in the Painting Diploma course. At this time I had no interest in pottery and cannot recall ever having seen a handmade pot. Pottery was not part of my diploma course but I was almost accidently persuaded to enrol in the night class as an extra subject. Pottery appealed to me at once. I was interested in the immediacy of the making methods and the direct contact with the materials. One of the books recommended was Leach's book, and Mollie Douglas was one of my teachers. I subsequently met Ivan McMeekin when I was a pottery teacher at the Canberra Technical College. At this time I made earthenware but while in Canberra I became friendly with Dr Lee Angel who had worked by himself to produce stoneware, learning from Leach's book. My research shows that he was the second potter in Australia, after Harold Hughan in Melbourne, to produce stoneware pots in what we now call the Leach-Hamada tradition and it was with him that I made my first stoneware pots from clay from Black Mountain, fired in Dr Angel's oil-fired kiln. 31
I was fortunate in having no previous exposure to pottery in that I was able to readily accept the Leach philosophy. Also I began potting at a most interesting time, directly after the war when these changes were taking place in the Australian art scene. My ideas were set then.
Douglas, Rushforth, McMeekin and I met regularly to discuss our directions and it is fair to say that we all agreed that what Leach had written appealed to us, and that pottery that we made would follow what we thought to be in the Song tradition of truth to materials, truth to function and a desire to create pots of the very highest order. McMeekin was of great value in our discussions as he was the one most versed in a practical way in stoneware production. Douglas, Rushforth and I, profited greatly from his generosity in sharing his vast knowledge and we all soon switched to making stoneware. From these informal meetings grew the idea that we should formalise our ideas into an organisation and the Potters' Society was formed. It was followed by other similar groups being formed in most states. Later more broadly based craft groups interested in all the crafts were formed under the general name of the Craft Association of the various states.
During the next ten years a number of significant events reinforced my commitment to the concepts of the Leach-Hamada tradition. My first teaching position was in Melbourne where the famous Kent Collection is in the National Gallery of Victoria. This collection enabled me to see for the first time Chinese pots of all historic periods. My visits were numerous. To this day I remember the glazes, the celadons, the juns, the temmokus and the clear yellows. Later in Canberra an exhibition at the Dutch Embassy brought more pots from China to my attention. This collection had been made in China by one of the secretaries whilst stationed in China and again I was confronted by the simplicity and the beauty of the pots and the magnificence of the glazes, and as it was an informal exhibition the pots were available for actual 'hands on' study. My regular visits to Mittagong to talk with Ivan McMeekin brought me into contact with his collection of not only Chinese pots but also the works of Leach and Michael Cardew. Many a meal was served on plates of one or the other. After I built myfirst kil n at Mount Kembla in 1955 my stoneware path was clear.
Other Influences In 1962 I was able to visit Japan for the first of a number of visits. Naturally my aim was to see as much as possible of the work of the potters I had read about. My centre was in Kyoto where a former Canberra student, Cecily Gibson, was studying. She introduced me to Fred Olsen an American potter who was working 32
there and who has since become well-known for his books on kiln construction. Also visiting Japan at that time was Daniel Rhodes the famous potter and author of potters' books44 and an academic from Alfred University. As it happened Fred Olsen was living in the studio of Tomimoto who at that time was very ill in hospital. Olsen was acting as caretaker and using the studio for his own work and I was able to make some pots there using Japanese clays, brushes and glazes.45
The first of the great Japanese potting families whom I met was the Kawai family. Kanjiro Kawai, about whom Leach had written, was already dead but his heir, Hiroshi, was living in the house where he kindly showed us many pots made by Kanjiro. Hiroshi also made pots though he never became well-known. He gave me a press-moulded rectangular bottle with a greenish dark glaze with poured contrasting glaze decoration, a valuable part of my collection. The whole of the garden area was covered with Kanjiro pots, hundreds of them lining all the pathways. The house is now the Museum dedicated to the work of Kanjiro Kawai and in it are many of the pots which used to grace the garden. It seems to be traditional in Japan for houses and workshops of famous people to become museums in their honour. Kanjiro, while working in the traditional way of which Leach wrote was also somewhat of an innovator. Some of his vases were unusually shaped. They were made for use in the tea ceremony or for inclusion in the special alcove called a tokonoma in the Japanese home used to display a flower or a few flowers accompanying a scroll on the wall I recall one shaped in a soft 'L form', which was unique. This impressed me for it meant that these traditional workers were still free to push the forms they used into new shapes.
The nephew of Kanjiro was Takeichi Kawai who carried on the fame of the Kawai family as potters. He lived in Kyoto and became a personal friend. He died in 1990. In the early sixties Takeichi had a very large workshop in what is called the Gojo area of Kyoto. The Gojo, literally meaning 5th Street, was the area where all the potters worked, most of whom, Takeichi included, had the large eight chamber noborigama climbing kilns. These werefired with wood about once per month by professional firemen and held anything up to 20000 pots. Sadly these marvellous kilns have all gone now, forced out by clean air and smoke control conditions. It must be said that in 1962 it was easy to find a kiln firing-one just followed the smoke in the Gojo. Takeichi Kawai was a member of the Yamato Mingei circle of potters and followed the ideals of a humble peasant potter though he was the head of a large and successful mini-factory. He designed all the wares made and
^Daniel Rhodes. Clay and Glazes for the Potter. Pitman, NY, 1969. ^Subsequently, I was informed that one of these pots had been acquired by Kondo Uso, the Professor at the Bidei University, for the University collection. 33 controlled a quite large group of potters and workers. The size of this large enterprise somewhat surprised me. Kawai took part in many phases of the work as the need arose, but most of the wares were produced by the workforce. Kawai was particularly well-known for his tea bowls and for a large array of press- moulded shapes. His glazes ranged from the dark temmokus through a blue known as ruli to a delicate celadon known in Japan as seigi. Many of the dark glazes used were based on the crushed rocks from the Kamo River which flows through Kyoto. This was of particular interest to me for I had studied the rocks in the lllawarra area with glaze making in mind and at about this time had been awarded the Fellowship of the Sydney Technical College for my thesis.46 My interest in these materials had been sparked off by Leach who had written of the Kimaicki stone at Mashiko as a glaze material and of the Kamo River Stone at Kyoto. Actually most of the potters there bought the rock glazes already prepared and I was unable to determine whether it was in fact the pure crushed rock or whether the rock was used simply as an ingredient in the glaze. The glazes used by Kawai were quite traditional, the celadon, temmoku, a greenish tea-dust and a clear white with applied blue brushwork.
In the workshop of Tomimoto I was able to see at first hand the results of a transition in his case from being a humble Mingei potter to one of great skill and sophistication. Towards the end of his life Tomimoto worked exclusively in porcelain with very intricate decoration in cobalt blue and many low-fired, coloured enamels. The work was in some ways related to the industrial wares of the factories such as Noritake, however it was decidedly individual and different. Tomimoto had an industrial background which he developed in an individual way. He used the conventional decorative methods of the Chinese and Japanese porcelain factories but in a new and refreshing way. His porcelain wares were fired to the high temperatures required and under the glaze he applied blue decoration of cobalt often in very simple lines. Subsequent firings at lower temperatures added reds, greens and gold, somewhat in the manner of Nabeshima and Imari wares, but without their copying of textile and conventional patterns. A great deal of Chinese and Japanese highly decorated wares rely to a significant extent not only on traditional patterns but traditional patterns that have been reduced to pattern books as the learning tools of the pottery industries. Travelling in China through the factories in the porcelain producing cities such as Ching te Chen one sees these books in the so-called 'design' sections where workers copy the patterns produced. Blossoms of various kind-plum, lotus, cherry-trees such as pine and plum, bamboo in its many forms, tigers, dragons and birds are
46ivan Englund. 34 reduced to a formal pattern and the design part seems to be confined to different combinations of the motifs. This is, of course, not very different from European practice. I am merely making the point that Tomimoto did not, in his highly decorative painting, merely copy the motifs so often used in porcelain. 35
B&fl
Tomimoto Plaque - Kyoto 1963 36
Tomimoto did at one time design a line of dinner ware for industrial production in which the cobalt blue decoration on the pure white edge of the flat wares contrasted with intersecting brush mark of intense red. He also produced many circular wall plaques on which he wrote a poem in cobalt blue with just one contrasting blossom in red and green enamel. Even without the translation of the poem it was easy to appreciate the beauty of the Japanese calligraphy.
Like many of the Japanese potters, Tomimoto had no qualms about expediting his pottery production. As the occasion demanded he would have expert artisans make moulds from his models. He was interested in the final work rather than in the mundane work expended in the manufacture. This surprised me. Many of Tomimoto's pots were simple elegant shapes with a translucent white glaze decorated with cobalt blue applied before the glaze firing and subsequently further embellished with red enamel, often with a poem. Japanese calligraphy lends itself to decorative effects. Some of the superb Japanese brushwork on Tamba Saki bottles so much admired by Australian potters might simply be a caption reading, "Drink Ito's Saki!" The use of the brush in calligraphy is regarded as an art form equal to painting, sculpture and ceramics and great attention is paid to fine writing.
From Kyoto I took a day trip to the traditional pottery centre of Tamba. The whole area is classified as a National Treasure. The kilns are similar to the big Chinese 'Dragon' kilns, a long upward-sloping tunnel without inner divisions, packed through openings at intervals up the hill and fired initially from a firebox at the bottom, then successively side stoked through small holes on both sides as the temperaturerises. The wares at this Tamba kiln site were exclusively saki bottles and jars and plant pots all glazed with a high iron glaze, called in Japan Kaki. Some had a splashed or poured glaze decoration of black. The shapes were traditional and had not changed over many centuries. The clay was a sandy yellow, rather sticky material, not as easily thrown as the Australian clays I had used. The light wooden Japanese potters' wheel was difficult to use at first, as I found when invited to make a few pots at the workshop of the Ichino brothers.
From Kyoto it was convenient to visit the big pottery cities of Seto and Tajimi. Seto produces industrial wares as well as pots and Tajimi is the centre for Shino glazes. Shino glazes are popular in Japan, often seen in the tea ceremony ware. The clay is sandy and porous and the glaze is white to apricot in colour. It is usually full of pinholes and often crawls leaving gaps in the surface. The tea bowls are decidedly asymmetric and the rims uneven. As one travels to broaden one's horizons there have to be some things which do not appeal. Shino to me is a technique that has never appealed, not even after having spent an afternoon with 37 the famous Arakawa, a Living National Treasure, who had produced a tea bowl which was acclaimed as the best Shino tea bowl that had ever been made.
I next went to the Bizen area near Okayoma. Bizen is another place where the same sorts of pots have been made for hundreds of years and they are good examples of the use of a special clay and special firing technique. A very black clay occurs a few metres under the rice fields. It is unique to the area. It is so highly regarded that at present no building is allowed until the clay is mined and stockpiled. The firing is usually continuous from four to seven days. No glaze is applied. The long firing with wood deposits fly ash on the pots and when the temperature is high enough the ash melts into a crude glass coating. The different areas in the kiln receiving different amounts of ash give differing results. Some pots are even fired in the fire-box and these receive heavy lava-like ash deposits. Further from the fire the ash becomes more like a glaze. Pots are stacked together and on top of each other to cause variations in the flame path, giving rise to variations in ash deposits. Small shards are also used to resist ash, resulting in different coloured areas. In the coolest part of the kiln rice straw is draped over the pots leaving red marks when it bums away. This is called hidasuki. My host was another Living National Treasure, Kaneshige Toyo. His family, together with the Fujiwarra family, had transformed the largely industrial use of these techniques into an art form. Most of the wares made by Kaneshige (and the Fujiwarra's and many others since) were either saki bottles, cups, or tea ceremony ware. It is not unusual for exhibitions in Tokyo galleries to consist of perhaps one hundred and fifty saki bottles all of the same shape, all about 150mm high and differing only in the way the ash deposits have decorated the pots. Western potters have followed this Bizen method of making pots and in some ways it represents a sort of Song tradition of exploiting a material and a technique to achieve a unique product. For myself, while appreciating the style, I was more interested in what might be called conventionally glazed pots.
Moving on to Kyushu I was able to see the Korean-based Karatsu wares which again were consciously crude, designed for the tea ceremony. At Arita I found porcelain wares that were almost at the opposite end of pottery making techniques from those I had seen at Tamba, Bizen and Karatsu. The whole of the Arita area seemed to be devoted to porcelain making. History tells us that in the 1590s, after an unsuccessful Japanese invasion attempt on Korea, a Korean potter was brought back and he discovered the very useful porcelain clay deposit which made possible, together with his expertise, the very important porcelain industry at Arita. There numerous factories produce high class porcelain Imari wares. At first these were of the 'blue and white' family, white porcelain glazes painted with 38 cobalt oxide in a wide range of patterns. Later Imari wares became more ornately painted utilizing not only cobalt blue but reds, greens, purples and golds in the form of low-fired enamels, much after the style of the highly-decorated pots of the same periods in China. Much of this pottery has been criticised as being too highly decorated often in patterns derived from textiles and are regarded by some as aesthetically inferior to other porcelain. More highly regarded are what are called Nabeshima wares which, while using the same techniques, exhibit superior standards of technical skill because they were produced not for a mass market but solely for presentations to feudal lords. Its colours were always harmonious, the designs were uniquely appropriate for bowls and plates and the enamels used often resembled the delicacy of water colours. The wares were produced for only a short period and were rarely exported. In Arita, in contrast to the many factories there, are two families which have continued to produce very personalized porcelain wares to the present day.
About 1660 a potter perfected Chinese enamel techniques and produced an orange-red overglaze colour which reminded him of aripe persimmon . The name of persimmon in Japanese is Kaki and this potter took the family name of Kakiemon. Kakiemon wares are noted for a milky white colour, with veiy careful brush painted designs and were a direct influence on European factories at Worcester, Delft and Meissen when European porcelain making became possible in the early 18th centuiy. Kakiemon was aimed at the export market.
In opposition to Kakiemon was another family named Imaemon which also specialised in the overglazing enamel technique and has continued to produce very highly regarded ceramics. I did not visit the Imaemon workshop until about 1983 where I met Zensho, the 13th generation Imaemon, who had been made an Important Intangible Cultural Treasure, which we call a National Treasure.
Eventually I went to Mashiko to meet the great Shoji Hamada. Mashiko is a couple of hours North of Tokyo. Hamada had made it his home many years before and Leach had worked there from time to time. I telephoned Hamada from Tokyo and he simply said, "come tomorrow, we arefiring th e kiln". He met me at the gate where the taxi dropped me. He was dressed as always in his baggy peasant clothes. His welcome was warm. I was shown the whole complex of pottery workshops. The Hamada property was large. There were three climbing kilns, one of which was firing and he had a small salt glazed kiln which he had built to fulfil a special order of 18000 beer mugs.
On the property were numerous large thatched farm houses. He had bought them and had them re-erected as living units and workshops. One contained his vast 39
collection of pots. "I buy anything that I think I could not make", he said. The collection contained Chinese pots from Han, T'ang, Song and Ming times. There were pots from historic Japan, Haniwa, Jomon, Yayoi, Sue, and of course pots by Bernard Leach. Two large gate houses were storehouses for his own pots. There were stacks and stacks of pots from his workshops and his own private works. A generous man, he presented me with one of his plates. The pots which I remember most clearly were those strong simple shapes both thrown and press- moulded with the fresh decoration of poured slip and glaze for which he was famous. The surfaces of the rectangular press-moulded bottles were often divided into square patterns of Kaki and cream glazes, upon which he usually superimposed a calligraphic decoration based on an early drawing of his of a sugar-cane shoot. The Kaki glaze was composed of the local building stone crashed to a powder and called Kimaichi stone. 40
Hamada Pots-Mashiko 1963 41
As mentioned before the Japanese word for persimmon is Kaki and the best Kaki glazes which are coloured with a large percentage of iron oxide have an orange colour not unlike that of aripe persimmon. This he used with great effect together with a black temmoku. Some of his greens were obviously based on copper though he used celadons too. His white glaze was a simple one which included a large percentage ofrice straw ash.
Hamada was meticulous about his glaze materials. On one occasion while seated at one of his low tables near a brightly burning fire—it was the middle of winter— he told me that wood ash was used in many glazes and he kept the various ashes separate. For example, the fireplace near which we sat burned only a special pine wood that was brought to him by local farmers and he washed that ash ten times before use. The building where pots were made was one of the large farmhouses already mentioned. It was light and aiiy. The clay was in the middle of the area, a mass of perhaps a tonne, covered, and from which the throwers cut their requirements. There were six or seven throwers using the light wooden Japanese wheels turned with a stick. Ware boards held pots on racks and outside in the open freshly thrown bowls were placed to dry. I was moved by this scene, exactly as described by Leach. The kiln which was firing was attended by most of the workers. Hamada told me that even on their days and time off all the workers turned up as usual. During the day Hamada excused himself to meet his box- maker from Tokyo to sign the box lids. He did not sign his pots but only the lids of the boxes in which they were stored and exhibited. While in Mashiko Hamada also introduced me to his neighbour and student Shimaoka and to another potter working in the same Mashiko tradition, a Mr. Sakura. Sakura-san showed me two plates made by Bernard Leach at his pottery during one of his many visits to Japan. 42
"I
Leach Pot-Mashiko 1963 43
This journey to Japan reinforced my feelings about the way I was working and the way I thought my future directions lay. Seeing the Japanese artists at work clarified many of the ideas I had about what Leach had written. Reading about the methods and aspirations of the Japanese potters was in many ways different from the reality of meeting and talking to them. I had gained the impression from A Potter's Book41 that the great Japanese potters worked and lived like anonymous peasants, individually turning out pots for everyday use, using whatever crude materials were available. But this was far from the reality. All the well-known potters I met were heads of teams of potters running large and well-organised workshops. They were revered by all. Many had been honoured by that marvellous title "Important Intangible Cultural Treasure"—equivalent I suppose to a Cultural Knighthood. Potters are ranked in Japan equally with the painters, sculptors, calligraphers, weavers and musicians. There seems to be no gulf, as in our society, between the "Arts" (painting and sculpture) and the "Crafts" (pottery, weaving, textiles). This is the sentiment expressed by Coplans when he says, "What distinguishes a work of art from that of craft is qualitative. A work of art is not concerned with the utilitarian, the rational and the logical. Its purpose is expressive, it is concerned with the aesthetic experience in its purest form".48 The prices paid for pots were equal to the prices painters get for their works. It was rumoured while I was in Japan that a collector-a Japanese-had paid US$25,000 for the famous Shino tea bowl made by Arakawa. Hamada's large plates were available for about A$200-400. What a contrast with Rushforth and Hughan, two of Australia's best potters at the time, who were selling pots for two or three Guineas, equivalent to A$4.20 and A$6.30!
Having been convinced by Leach of the legitimacy of making pots in a straightforward way, based upon a container or vessel, and with the firm idea that these shapes depended largely on a 'truth to materials' approach, I was able to choose more confidently the sort of Japanese influences I favoured. Hamada was the dominant figure in my view. I appreciated his pots for their confident simplicity, for his use of a quite limited number of, for him, appropriate glazes and I saw in his glazing techniques of poured glazes one over another something that appealed to my way of thinking about decoration. The poured glaze technique appears to me to be one which is spontaneous, immediate and peculiar to the potter's materials. The closest anything in the wider art world comes to it is the poured and dripped paintings of Jackson Pollock. It is a technique that I have used consistently in my own pottery. With practice some control is possible, though their are some accidentals that have to be evaluated and dexterity underpins
47 Leach. A Potter's Book. 48John Coplans, in Garth Clark. Ceramic Art. p. 153. 44 artistic merit. Unlike conventional painting, where there is the opportunity to paint over or scratch out undesirable passages of paint, the potter gets only once chance for the poured decoration to be right. Some courage is needed. So the Mashiko wares took an important place in my pottery thinking.
While I appreciated the effects of firing on clay occasioning subtle colour changes and textures, and the deposition of fly ash melting to a natural glaze, and while from time to time I experimented with the Bizen technique, my real interest was directed to conventional glazes. The unglazed wares of the Bizen potters, Kaneshige and Fujiwarra, owe everything to thefiring procedure and the choice of clay. Often the results are what the Japanese call shibue, a word that Leach says is almost untranslatable but could be thought of as austere, subdued or restrained. Etymologically it means "astringent". The word implies almost the opposite of the unctuous, tactile beauty of the Lung Ch'uan celadon glazes of the Song period.
Some potters of my generation have in the past been accused of blindly copying the shapes of Chinese or Japanese pots. To refute this claim it is pertinent to consider, for example, the pots of the Song times. Perhaps the most famous and certainly the most published Song pot is a vase of a shape called Kinuta. "Kinuta" means "mallet". The Song Kinuta pot has a shape relating to the mallet used by wood and stone carvers. The shape is made of several sections luted together, basically a cylindrical shape in the main body surmounted by another cylindrical shape above of smaller diameter-the handle of the mallet. This "handle" shape ends in a wide flaring mouth. Two handles are attached and these are described as "bird neck and head handles". Many Chinese wares have handles of animal shapes, such as elephants and dragons and this sometimes extends to the knobs on the lids of covered jars. I do not see much evidence of this type of design flooding the studios of Western potters. The glaze is the celadon which has been admired for a thousand years made from feldspar and coloured by the small amount of iron oxide inherent in the glaze materials as impurities. This iron oxide in the glaze, fired in an oxidizing kiln, will result in various degrees of amber depending on the amount of iron but if fired in a reduced atmosphere the iron oxide is changed so that the colour is green. The Chinese kilns which were fired with wood demanded great skill in operation but the Song potters, backed by literally thousands of years of tradition, were masters of the art. The colour of the celadon most admired is one that tends to be blue-green, although celadon can be of a number of different greens. Cox quotes a Chinese reference to the colour as "egg white", noting that in China ducks eggs are always pale blue or pale green, and further says the colour should be "blue like the sky after rain"49. The Lung
49Cox, p. 197. 45
Ch'uan celadons are noted not only for their colour but also for their texture. The old Chinese critics wrote in terms of "rich and unctuous, lustrous or fine and glossy". Later Ming writers used descriptions of the texture as "transparent and thick like massed lard". Surely something is lost in the translation.
Another shape much used by the Chinese and which has not been favoured by Westerners is the incense burner. This is usually a deep, three-legged bowl with elephant head handles. If a pot was provided with a cover (even vases sometimes had lids) it was often decorated with realistic Chinese lions. A vase with a long neck could have a stalking tiger modelled around it and one early Lung Ch'uan vase had a dragon, chicken and reclining figure modelled around the shoulder. It is only in recent years that I have noted the use of such modelled figures on Australian pots, the favourite animal being the frill-necked lizard, and of course one remembers in the middle of this century the ubiquitous Koala ornaments, mostly in painted plaster, which almostrivalled the famous flying ducks seen on many walls. The wares from the Lung Ch'uan kilns were destined for the Emperor's Court, so pots sometimes had additions that were an adjunct to the luxurious surroundings. For example, large wine jars with small tubular additions on the shoulders in which flowers could be placed were made in great numbers.
Of course there are many Chinese pot shapes which could be described as universal and directly related to the forming action of the material on a potter's wheel and these are the ones used by Western potters. The shapes which form naturally on a potter's wheel are composed of cylinders with outward and inward curves and the combinations of these are almost limitless. The old Chinese pots include those with long necks and those with short, globular and spherical vases, all of which constitute the normal range of shapes made by potters everywhere whether they have seen Chinese pots or not.
The main thrust of influence of Eastern pots on potters in Australia in the immediate post-war period of the forties and fifties came from Leach and his English followers. The Leach book50 began the Australian interest in English pottery and the contact with Leach, Cardew and Harry Davis was personal because of their visits to Australia. These potters visited Australia usually to conduct workshops, give demonstrations and have exhibitions. The influences from Asia and the robustness of English country pottery was added, sometimes with amusing manifestations. For example, many Australian potters produced cider jars!-surely a misdirected effort if the aim was to make utilitarian wares as Australia can hardly be compared with Somerset. It should be noted that all these
^Leach. A Potter's Book. 46 influences were important for it enabled potters to sort out for themselves the directions their work would take. Absorbing these influences and working through them while refining skills enabled Australian potters to become independent as their own styles evolved. This is not to infer that there is a single Australian style as yet and it might be argued that there is little need for it on the grounds that pottery making is a universal art activity. In any case I maintain that because of Australia's short history (in the European occupation sense), and the period in which English settlement took place there is no Australian tradition of pottery. The late 18th Century, when the First Fleet arrived, had seen therise of industrial pottery in England which led to the demise of much village and local pottery. In Australia several potteries were set up in the 19th Centuiy in various centres but they were mainly of the factory type which produced wares of the debased industrial ranges similar to those of England. This was understandable as our early settlers were in no way Australians. They were simply transferred British. Also, because Australia was in pioneer mode there was little time for most people to indulge in art or craft activities. It was probably from about the 1880s through to the time of Federation that there was the feeling that the people in Australia were 'Australians'. It was only in 1942/43 that thefirst rea l break in our colonial past came when Australians realised that they were in fact a nation separate from England, although this realisation was not enough for us to stand on our own feet and there was a transferance of our dependence to the USA.
Peter Timms, the Australian writer, has argued that perhaps the start of Australian studio or artist pottery could be traced to the hand-painted porcelain in the late 19th Century.51 As these were factory produced pots decorated by hand I would dispute this assertion. A true studio or artist pot would need to have been made as well as painted by the artist.
My early pots were fired only to earthenware temperatures simply because the kilns available to me (and others) were electric-fired, capable only of reaching low temperatures. However, true to the materials approach, I dug and prepared my own terracotta clay and while working in Wollongong I perfected a successful amber glaze utilizing the latite rock of the Berkeley flow which outcropped near my home at Mt Kembla. Having settled more or less permanently in the Wollongong area after moving around in teaching positions I was at last able to build an oil-fired kiln capable of achieving the high temperatures required for making stoneware pots. Again my interest in materials dominated my pottery thinking and I made an in-depth study of the local igneous rocks for their value as glaze materials. Over a number of years I studied the geology of New South
51Peter Timms. Australian Pottery 1900-1950. Shepparton Arts Centre, Shepparton, 1978. 47
Wales where there are many lava flows and dykes, the results of ancient volcanic action. In several cases quarries were still in production so thatfine material was obtainable as crusher dust making testing very simple. The dykes were not so easily located but I was able find most of those that I considered worth pursuing after researching the NSW Mines Department book by Harper, The Geology of the Southern Coalfields of NSW.52
Apart from the basalts and latites there exists in the Illawara area a sill nepheline syenite and a deposit of tinguite, both of which are prized because their compositions make possible much paler glazes than those of the high iron rocks. My work included the identifying and collection of samples and reducing them to fine powder suitable for glaze testing. The glazes were calculated using the Seger Formula and fired to stoneware temperature. This work resulted in a thesis entitled The Application of the Igneous Rocks of the lllawarra Region to Stoneware Glazes in Studio Pottery. 53 For this I was awarded the "Fellowship of the Sydney Technical College" (FSTC) in 1962. As mentioned above I had made a successful earthenware glaze from the Berkeley Latite and later when my attention turned to 'middlefire' processe s I made rock glazes in that firing range as well. Apart Iron the rock glazes my pursuit of stoneware led me to develop for my use the traditional glazes of the Chinese and Japanese potters. Many of these were the dark glazes coloured with large amounts of iron oxide such as the temmokus, the kakis and the tesshas of the Japanese. I also spent much time in the study of celadon glazes, a time-consuming pursuit into a very broadfield. The only person in Australia who was an authority on these at the time was Ivan McMeekin because he had inherited first-hand knowledge from Cardew and indirectly from Leach. My various trips to Japan, the Phillipines, Thailand and Hong Kong enabled me to see live examples of celadons of various types so that I became aware of their beauty and the technical problems involved in their making. I made my version of 'blue and white' and for years have aimed at the elusive flambe- and copper red glazes. I had a brief time firing salt glazes using my own kilns and also having wares fired in industrial brick and drain pipe kilns. However my sustaining interest was in conventionally glazed pots.
52LF Harper. Geology and the Mineral Resources of the Southern Coalfields of NSW. 53Ivan Englund. The Application of the Igneous Rocks of the lllawarra Region to Stoneware Glazes in Studio Pottery. 1962. 48
Chapter 4
THE MIDDLE FIRE GLAZES.
In the early sixties I set myself the problem of improving the quality of the pots being made by my students at the Wollongong Technical College. The only prepared clays available at that time were a terracotta from Chullora in Sydney and an industrial white earthenware. The glazes used were exclusively based on raw lead fluxes, which while technically useful, resulted in rather harsh colours. Fired at the earthenware temperature of about 1060°C the glazes were extremely shiny and this was at a time when the undecorated matt glazes from Sweden were making their impact on the Australian market. Making stoneware was not possible because the College kiln was not capable of firing to the required temperature. The fired earthenware was also very brittle, resulting in wares that were not very functional because they chipped and broke easily. I had decided that the pots would be stronger and more chip-resistant if the clay was fired to a higher temperature. This higher temperature I decided, after some tests in my own stoneware kiln, should be about 1150 to 1160°C. A test firing in the old College kiln proved that, with encouragement, it could reach that temperature. I then set out to evolve suitable glazes for that temperature.
As stated earlier there is a large body of information about earthenware because for centuries it constituted most of the production of both individual potters and industrial factories in the West. Even in China in T'ang times a great deal of ware fired to earthenware temperatures was produced, including the well-known T'ang horses and camels glazed with amber and green lead glazes. The English country pottery, the Faience of France, the Majolica of Spain, and later of Italy and the Delft of Holland were all earthenware pots.
At the lower end of the firing range there existed a substantial interest in glazes fired at temperatures much lower than the conventional earthenware. This area is generally known as "Raku". Its inspiration was the low-fired tea bowls of the famous Raku family which still functions in Kyoto. The so-called raku wares of the East are fired at temperatures of 1000°C and often much less, and here too there is a great deal of information. 49
In the area of high-fired wares, stoneware and porcelain, the information is voluminous, especially in the years since Leach's book led to a stoneware revolution in the West. Now there are dozens of books dealing with the subject and ceramics magazines publish articles of all kinds together with recipes by the hundreds if not the thousands. Every potter has his or her own 'secret' recipes which is amusing when one thinks of the thousands published. A good deal of the mystery of glazes lies not only in the recipe but also in the firing. In the words of Delaherche, "What miracles these twelve hundred degrees of heat can perform".54
In what I call the 'middle fire' area, the temperature range between 1100°C, the upper limit of earthenware and 1200°C, the beginning of stoneware, there is less information. Therefore, for the past thirty-five years I have worked in this firing range, culminating in this current research. I dubbed my early work on these glazes "middle fire" to attempt to give it a status of its own. Potters used to use terms like "high fired earthenware", which is acceptable but not the most useful descriptor, especially if used to conveniently describe earthenwarefired abov e the usual temperature, often because a kiln had been overfired. Another term was "vitrified earthenware". This was a nonsense term because by definition earthenware is not vitrified. The definition states that earthenware typically has a porous body. Similarly stoneware potters sometimes called their underfired wares "Low Fired Stoneware" but stoneware by definition has to have a vitrified clay body.
The other major focus of my work across my career, and therefore in this reasearch, has been to concentrate on raw-glazing and a once firing procedure. It should be noted that the majority of pottery produced world-wide is once-fired if we include all unglazed wares such as plant pots, tiles, industrial items like sanitary fittings and some factory wares that are spray glazed when completely dry. Add to this list salt glazing in which the pots are glazed by fumes caused by the introduction of salt into the kiln at high temperatures. Many of the once firing techniques in the low temperature range favoured by some potters include raku ware, primitive firing in a bonfire, saw dust firing in a container of sawdust and pit firing where the pots are placed in a hole in the ground, covered with sawdust and timber which is ignited and left to bum.
In contrast, probably most of the ceramics produced by artist potters and studio potters are fired twice. The first firing called the biscuit firing (or sometimes the bisque) to about 900° or 1000°C is for the puipose of transforming the clay into a hard easily handled material. The pots are then glazed and fired a second time to
54August Delaherche, in Clark, p. 53. 50 temperatures suitable to mature the glazes. Because all my work over a period of more than forty years has been produced by once firing I decided to follow this method in my research into the "middle fire" temperature range. A comparatively small number of potters sufficiently appreciate the advantages of once firing to use it as their standard procedure. These advantages include the obvious saving in fuel costs by eliminating a complete firing, a considerable time saving because the setting, firing and unloading of biscuit kilns are not needed, and there is what I call an artistic continuance of thought in that the pots are designed, made, glazed and decorated in sequence without interruption. The ecological reasons for using less fuel are obvious with respect to greenhouse gases.
It is possible that the once fire method could slow the working pace of a production potter as pots have to be glazed as soon as they are ready but I would imagine that this would be compensated for by the time savings mentioned above. Raw glazing in the teaching situation may be unsuitable for students attending only once per week, with difficulties in arranging for the pots to be in the right condition at the right time without big storage areas but in colleges and universities where students attend full-time there should be no difficulty.
The technical problems inherent in raw glazing can be minimised. Application is no more difficult than using slips. The glaze is applied when the pot has reached its final shape following throwing or building and is still damp at the stage potters call 'leather hard'. If the clay is too dry it may crack when glazed and if it is too wet the handles may fall off. It is simply a matter of practice. I have used a great variety of clays over the years and have had no major difficulties with any of them. The glaze can be applied in any of the usual ways by dipping, pouring, spraying or brushing. Whichever method is used, the application should be much thicker than on bisqued ware, because the glaze is applied to a non-porous, leather hard clay and there is no absorption to assist in building up the glaze layer. Small pots can be successfully coated by pouring and dipping but there should be an interval between first pouring the inside and then dipping the outside. If too much water enters the clay body the pot may collapse and/or appendages may sag or fall off. Again because the ware is still in the damp, raw condition there is a limit to the size of pot that can be dipped. With symmetrical shapes the glaze can be applied with a brash while the pot revolves on the potters' wheel as in slip application. With very large pots or those of very complicated shape the glaze can be painted on in a number of layers, with a short time between applications. Because the ware is not porous as in biscuit wares brushing is very simple. 51
The glaze is different from the biscuit type in a physical sense in that it must contain various amounts of high shrinkage, sticky materials to adhere it to the raw pot. Bentonite is a clay material with extreme plasticity which allows the glaze to not only adhere to the damp pot but also to shrink with it as it dries. Without the bentonite component ordinary glazes applied to a damp pot will not adhere but simply flake off during diying. In other respects the chemical composition of the glaze is almost exactly the same as for the ordinary biscuit type glaze and there is no difference in appearances when fired.
The glaze materials are weighed out in the usual way and then thoroughly mixed in the dry state. This disperses the bentonite through the other materials. If water is poured on to bentonite it tends to make it into a gluey mass. The diy mixing helps prevent this. It is important not to add too much water. With ordinary glazes if too much water is added the excess will come to the top after standing and can be poured off but with bentonite glazes the glaze materials always stay in suspension and there is never any water on the top to be poured off. Therefore water should be added sparingly. For 1 kg dry glaze about 750 to 800 mis of water will be required. It is best to add about 700 mis of water initially, stir thoroughly and then top up with small quantities until the glaze is of the consistency of thin cream. I use a paint stirring attachment in an electric drill and I have found it to be the most efficient tool in a studio situation. I seldom sieve the glazes as all the materials are finely ground when purchased and so the glaze can be used immediately. After standing for some time the glaze will appear to be very thick. This is because bentonite is a thixotropic material that causes the glaze to become jellified. It will become fluid again with stirring.
Bentonite and Once-fired Glazes The calculations involving the use of bentonite as a glaze material need some explanation. Some materials are simple in that they supply only one oxide to the glaze. For example, whiting which is calcium carbonate, CaC03, loses the carbon dioxide in the fire so that only the calcium oxide, CaO, takes part in the calculations and the glaze composition. Bentonite is more complicated. It is a clay-like mineral formed from volcanic ash and is reputed to be the most plastic natural material.
There are many bentonites each differing in chemical composition. For many years I used Western Australian Bentonite in my stoneware glazes as did many of my contemporaries. However this material is no longer commercially available, probably through lack of demand. Many potters use imported American bentonite 52
from Wyoming but I decided to use an Australian bentonite mined at Wingen in New South Wales, supplied by Commercial Minerals Ltd. They have various grades, mine being dubbed PV53. The switch to this bentonite meant that I had to recalculate the formulations for all my stoneware glazes. Some alterations were dramatic. However it is a perfectly acceptable material and I have used it in my once-fired glazes in stoneware, in the earthenware glazes developed for the Montoro Company for use on their original roofing tiles and now in my research into the 1100°-1200°C glazes.55
In the simplest terms glazes are very like glass. In nature several materials are classed as "glass formers" the most common of which is silica. Glass formers as the name suggests are materials that would form a glass when melted alone at a certain temperature. If silica is subjected to a sufficiently high temperature it does melt to a glass and it is used in this form in many ways. But for potters it is not much use because pure silica begins to melt at about 1713°C far too high for general pottery making and beyond the capacity of most pottery kilns. To make glass or glaze at a suitable temperature it is necessaiy to add to the silica materials known as fluxes which combine with it to produce melting at lower temperatures. The list of fluxes used in pottery includes Lime (CaO), Magnesia (MgO), Potash (K2O), Soda (Na20), Barium Oxide(BaO), Zinc Oxide(ZnO), Lithia (Li20) Strontium (SrO). Lead oxide (PbO) used in earthenware is not used in high fired wares as it volatilises. In any case most potters have eliminated lead entirely from their work for health and safety reasons.
The main differences between glass and glaze is that glazes usually incorporate a proportion of alumina, AI2O3, in the composition as this helps to control the flow of the melted glaze. With glass makers this is not a problem because their articles are formed of the molten material and then left to harden when cooled.
The glaze maker has to solve a number of practical problems even before considering the aesthetics. The glaze must melt at the required temperature. It should not flow so much that it runs off the pot. It ought not to craze and it should be a good base for colour additions.
The melting depends upon a number of factors. The proportion of fluxes to alumina and alumina to silica are the important ones. Here the work of the German chemist Herman Seger should be mentioned. Historically glazes had simply been mixtures of ingredients which were found to work probably by trial and error
55Note - Since this work has been completed I have been advised by Commercial Minerals Ltd that Bentonite PV 53 is no longer available but but they recommend two similar materials which are numbered Bentonites PI and CL 300. 53 methods over hundreds and thousands of years. The recipes were closely guarded secrets but Seger noted that sometimes glazes used in different parts of the country while having different recipes were very similar when melted. For example one pottery might have a glaze made of whiting, ash and their local clay while another whose glaze was similar might use burnt oyster shells, beach sand, and local but different clay. Seger set out to try to find a way to compare the glaze ingredients. He decided to reduce the glaze ingredients to the oxides in an analysis and he then evolved a formula by which the oxides in one glaze could be compared to those in another. In this way it was possible to discover that a glaze used in one pottery using certain materials was in fact similar to the glaze used in a second pottery though the ingredients were quite different. The Seger Formula which resulted has been used widely ever since because it makes possible not only comparisons of glazes but an easy and reliable way to calculate unique personal glazes including those utilizing local igneous rocks.
The essentials of glazes are silica to form a glass, alumina to control the flow and fluxes to assist in the melting process. It is the control of these three materials that enables potters to formulate glazes that will melt at various temperatures 54
Chapter 5
WORKING THE SEGER FORMULA
The range of available computer software programs for calculations in glaze technology has grown in recent years and is well-documented in the literature. For example, in the American Journal Ceramics Monthly articles by Harold J McWhinnie from the University of Maryland are prefaced by a statement about his use of a software program to build his databank of glazes. He refers to calculations done in this way pre-1983 although he does not mention a specific program56. Pottery in Australia has also printed articles demonstrating spreadsheet calculations for glazes.57 Australian ceramicists use software such as Insight and Hyperglaze. I have experimented with a Macintosh HyperCard program58 for some of my calculations and I have also included an example using an IBM Multiplan Spreadsheet.59 However, as I do not have my own computer I have used an electronic calculator to formulate the bulk of my glazes.
Before demonstrating the method of calculating complex materials such as bentonite into glaze recipes it is as well to illustrate by a simple example the steps needed to transform a Seger Formula into a glaze recipe. I will use the widely published Calcium-Alumina-Silica eutectic which melts at Cone 4(1160°C). A eutectic is a mixture whose constituents are in such proportions that it melts and solidifies at a single temperature that is lower than the melting point of the constituents or any other mixture.
The Seger formula is set out in a three column pattern and for this combination is as follows:
1 CaO .35 A1203 2.48 Si02.
The fluxes are listed in the first column, the intermediates in the second and the acids or silica in the third. The usual convention in Seger calculations is to work to two decimal places.
56Harold J McWhinnie, in CM Nov 82, Dec 83, Sept 84, Dec 91, Feb 93 and April 91. ^Pottery In Australia. Vol 58Macintosh HyperCard developed by Daniel Midwinter Hampton ^Spreadsheet developed by Denis Chapman. 55
The prefixed numbers to die chemical compounds are molecular parts or molecular proportions. This formula converts to the following recipe:
Material % Weight Whiting 33.7 Kaolin 30.4 Silica 35.9
When using the Seger formula the flux column always has to add to one whole number or unity no matter how many oxides it includes. With the fluxes at unity the amounts of alumina in the intermediates column and the silica in the third column can be varied according to the temperature required for the glaze.
Sample Calculation to Transform a Seger Formula into a Glaze
Cone 4 Eutectic Glaze
A table is set up as follows:
Step 1 Formula Required Materials 1.0 CaO .35 AhCh 2.48 SiO?
The workings should always be set out systematically as above to minimise errors in the calculation.
Taking the oxides in the 'Formula Required' column in order it will be found that 1.0 CaO or calcium oxide is needed. Calcium oxide is not normally found in the studio in that form so a material containing this oxide is needed. The usual material supplying calcium oxide is whiting which is calcium carbonate or CaC03.6° The thermal decomposition of the whiting produces calcium oxide which enters the glaze while the carbon dioxide exits via the flue during firing. Whiting will supply CaO in the glaze. The formula requires 1.0 CaO so whiting is entered into the materials column with the required amount (1.0) next to it. The 1.0 is transferred across under the CaO column and subtracted resulting in zero which means that the 1.0 whiting will supply all the CaO required.
6^The convention with Seger formulae is to denote oxides in the form in which diey enter fusion. 56 57
The table will look like this:
Formula Required
Materials 1.0 CaO 35 AWQ3 2.48 SiOo Whiting 1.00 1.00 .00
Step 2 Next the alumina or AI2O3 is calculated. It is usual to use clay to supply the alumina. The accepted formula for clay is: -
1 AI2O3 2 Si02 2 H2O
The water boils off in the kiln. The formula requires .35 AI2O3 and as kaolin is the usual supplier, in my glazes, kaolin is entered in the materials column, transferred over to the AI2O3 column and subtracted again resulting in zero. So the .35 moles of kaolin fulfills the alumina requirement. But because clay also has twice as much silica in its formula .35 will not only give that amount of alumina but also twice that amount of silica which is .70. This is transferred to the silica column and subtracted leaving 1.78 more silica needed. Kaolin is the usual form to use in glazes because its purity allows the formation of white or clear transparent glazes but if that is not a consideration any clay can be used.
The table now looks like this:
Formula Required Materials 1.0 CaO .35 AbOi 2.48 SiO Whiting 1.00 LOO .00 Kaolin .35 35 M .00 1.78 Step 3 1.78 more Si02 is now required. Si02 is supplied by as silica, flint or quartz and it supplies only the one oxide. So 1.78 is entered in the materials column as silica, the amount is transferred across under the Si02 column and subtracted resulting in zero. The complete table now looks like this;
Formula Required Materials 1.0 CaO .35 AbOi 2.48 Si09 Whiting 1.00 1.00 .00 Kaolin .35 ,35 JO .00 1.78 Silica 1.78 1.78 .00
The table indicates that the oxides required will be supplied by the materials in that column. The next step is to transform the numbers against the materials into a form that can be weighed up as a recipe. 59
Step 4 To do this each material is multiplied by its molecular weight to calculate a recipe format.
Weight Ratio %
Whiting 1.00 x 100 100.00 33.7
Kaolin .35 x 258 90.3 30.4
Silica 1.78 x 60 106.8 35.9
297.1 100
The Molecular weights are found in glaze chemistry reference books. Some works leave the recipe as it appears in the weight ratio column but it is more convenient to calculate it as a percentage for easier comparisons of glazes and it is also simpler when making colour additions. The recipe is now shown as parts by weight. 60
Chapter 6
BENTONITE AND ONCE-FIRED GLAZES.
To use the Seger Formula method to calculate a glaze recipe it is necessary to know the chemical analysis of the materials used. For calculation with the conventional and much used materials it is often assumed for convenience that they are in fact pure and so the figures allotted to them may be slightly different from actual composition. For instance, in the above example the whiting is assumed to be pure but it may actually contain only 99% CaO and this figure would also mean adjustment to its usual molecular weight of 100. But the difference between the pure and the actual is so small that in normal practice the difference is ignored. Whiting is usually 99% pure, and kaolin has a similar purity. The assumed molecular ratio of kaolin is 1 AI2O3 2 Si02 2 H2O but that would apply to very few kaolins for most clays have in their make up small amounts of 'impurities' and the relationship of alumina to silica is rarely 1 to 2 exactly. For absolute accuracy the exact analysis of the clay would be needed but in practice- the assumed and regularly used formula for clay is adequate. This also applies to most of the other main glaze materials such as the feldspars and nepheline syenite. Some pottery books list their recipes without nominating specific materials (eg Leach). However the two variable materials, kaolin and feldspar, that I use do in fact conform closely to their accepted assumed compositions so I use them as is in my calculations. Others may vary significantly and such variations need to be accounted for in Seger formula calculations, as shown below for bentonite. The kaolin is mined at Home Rule in New South Wales and was marketed by a company called Austral Rock Milling. The analysis supplied was:
Kaolin
Si02 46.41 AI2O3 36.49 MgO/CaO 1.03
K20 .32
Na20 1.18
Fe203 1.18 61
Ignoring the tiny amounts of fluxes which are not large enough to be significant in the calculations, the formula is:
A1203 1 Si02 2.16
The given ratio of 1:2.16 is so close to the theoretically relationship that the difference can be ignored.
Austral Rock Milling also supplied the Broken Hill feldspar which I use. Its analysis is: Feldspar
Si02 66.31 AI2O3 19.03
Fe203 .20 MgO .50 CaO .70
Na20 1.13
K20 10.71
The formula is:
MgO .063
CaO .069 A1203 .989 Si02 5.847
Na20 .265
K20 .603
Most potash feldspars contain a proportion of sodium but these are usually combined so the fluxes column could read MgO/CaO .132, Na20/K20 .868 totaling 1.00. The relationship between the A1203 .989 and the Si02 5.847 is 5.912 which is very close to the assumed 1:6. The use of the commonly assumed molecular ratio for feldspar (1:1:6) is justified because the difference from the BH feldspar is minute. The other materials pose no problems with regard to variations in analysis.61
When using an untested new material it is necessary to have the analysis and from this calculate its Seger formula and its molecular weight. Bentonite is a case in
61 Austral Rock Milling was absorbed by other companies many years ago but as I have always obtained my materials in large quantities I still have supplies of the above materials. 62 point. In fact, bentonite is a material which varies greatly in composition from area to area and supplier to supplier and in my experience it is unsatisfactory to use a 'typical' figure because I do not believe that there is a typical bentonite available. As mentioned earlier my switch from Western Australian bentonite to the material from Wingen, New South Wales (PV53) necessitated complete recalculation of my stoneware glazes.
Not only are the analyses of these two bentonites different but they are physically different as well. The Wingen material is not as sticky nor does it shrink quite so much as that from Western Australia so more has to be incorporated into a glaze for satisfactory adhesion to the pot. Whereas 13% Western Australian bentonite in the recipe was satisfactory I have found that about 18% to 25% Wingen (PV53) is needed for the same adhesion. This is not a drawback. It is just an illustration of the need to know the materials.
Sample Calculation of the Seger Formula for PV53 Bentonite
Step 1 Divide each oxide in the analysis by its molecular weight:
PV53 Analysis Mol/wt
Si02 59.5 _ 60 .992
AI2O3 21.0 - 102 .206
Fe203 6.5 - 160 .041
CaO 1.0 - 56 .018
MgO 1.8 - 40 .045
Na20 1.2 - 62 .019 H2O 8.3 - 18 .461 63
Step 2 Arrange the results into the Seger Formula pattern which lists the fluxes in the first column, the intermediates in the second column and the silica in the third. In the fourth column the water is listed but as it takes no part in the actual glaze it is ignored here but has to be included in the calculations for the formula weight.
.018 CaO .045 MgO .206 AI2O3 .992 Si02 .416 H2O .019 Na20 .041 Fe203
Step 3 In order to normalise the weight analysis to a value of one molecular unit of fluxes the Seger formula for a glaze demands that all the figures above have to be divided by the sum of the figures for the fluxes in the first column. Because bentonite is a clay material the "clay convention" is applied, as described by Michael Cardew in his Pioneer Pottery.62 It denotes that for purposes of calculation the alumina in thefinal Seger formula must appear as "one" or unity, so all thefigures above are divided by the molecular parts of the AI2O3 (.206).
Seger Formula of PV53
.087 CaO
.218 MgO 1.000 AI2O3 4.816 Si02
.092 Na20 .199 Fe203
62Michael Cardew. Pioneer Pottery, Longman, London, 1969. 64
Step 4 To find the formula weight of PV53 multiply each oxide by its molecular weight and add.
.087 CaO X 56 = 4.872
.218 MgO X 40 = 8.720
.092 Na20 X 62 = 5.704
1.000 AI2O3 X 102 = 102.000
.199 Fe203 X 260 = 31.840
4.816 Si02 X 60 = 288.960
2.238 H2O X 18 = 40.204 483.574 round up to 484
Sample Calculation of a Glaze Recipe Incorporating PV53 Bentonite.
Parmelee's63 published formula for a "bright glaze" at cone 4 is used as an example of incorporating the PV53 bentonite in the glaze calculations. The bentonite is used in a once-fire glaze to cause the glaze to adhere to the damp pot and oxides in it have to enter into the calculations. As already mentioned about 18% of bentonite is needed in a glaze for the proper adhesion so the bentonite is the first material to be calculated. Previous tests have shown that this equates to . 13 molecular parts of PV53 in the materials column.
63Cullen W Parmelee. Ceramic Glazes. Chicago Industrial Publishing, Chicago 1951. 65
Step 1 PV53 bentonite is entered in the materials column followed by the multiplier figure .13.
Step 2 Each oxide in the Seger formula of PV53 is multiplied by .13 and the result entered in the appropriate oxide column. This number is then subtracted from the amount shown in the 'Formula Required' line. The remainders then indicate how much (if any) of that oxide is still required and which will be supplied by other materials.
Step 3 .23 K20 is needed.next and this will be supplied by potash feldspar. Feldspar is entered into the materials column together with the figures .23. The
.23 K20 is supplied by the .23 of feldspar so the .23 is entered under the K20 column and subtracted. The result is zero and this indicates that all the K20 requirement is satisfied. However feldspar also contains A1203 at the same rate as
K20 so .23 must be entered in the A1203 column and subtracted leaving .07 still to be found. In addition feldspar has in its composition six times as much Si02 as
K2Oand A1203 so the figure to be transferred to the Si02 column is 6 times .23 which is 1.38. After subtraction .89 of Si02 is still needed.
Step 4 Dolomite is next in the materials column with .03 as the multiplier figure. Dolomite contributes equal amounts of MgO and CaO so it supplies all the MgO required .03 and also .03 of the CaO. The subtraction in the CaO column shows that .31 is still required.
Step 5 Whiting is the usual material to supply CaO so it is entered into the materials column with the .31 still needed. This number is transferred to the CaO column and subtracted. The zero indicates that the CaO requirement is satisfied.
Step 6 Zinc oxide is next entered into the materials column together with the .21 needed. The .21 is subtracted and the resultant zero means that no more is needed.
Step 7 Barium carbonate is entered in the materials column with .15. This is subtracted from the amount required and again the zero shows that no more BaO is needed. It should be noted that barium carbonate is a poison and should be handled with great care.
Step 8 .07 A1203 is still needed and kaolin is the material to supply it. It is entered in the materials column with the .07, the subtraction made resulting in zero. Kaolin contains twice the amount of Si02 as it does A1203 so .14 is subtracted from the Si02 column leaving .75 still to be found. 66
Step 9 Silica, quartz or flint is entered into the materials column to supply Si02 together with the .75 needed. After subtraction the zero result shows that all the
Si02 requirement has been satisfied. A check across the table will show that all the oxide requirements have now been satisfied.
Step 10 It is necessary to transform the figures and materials in the materials column into a form uhat will enable them to become a recipe. List all the materials and their molecular ratios in a column.
Step 11 Multiply each material figure by its molecular weight. Molecular weights are found in many ceramics texts.
Step 12 The resultant figures now constitute a weight ratio and could be used as parts by weight or recipe.
Step 13 However it is more convenient to convert these figures to percentages. As already mentioned it makes it easier to compare recipes and to make colour additions. 67
Glaze No.40.22 Cone 4 (Seger) 1160°C
Formula Requii •ed Materials .23 .01 35 .21 .06 .15 .43 2.90 K2O Na20 CaO ZnO MgO BaO AI2O3 Si02 Bentonite .13 .01 M M dl ,63 PV53 .00 .34 .03 .30 2.27 Feldspar .23 ,23 21 1.38 .00 .07 .89 Dolomite .03 m M .31 .00 Whiting .31 31 .00 Zinc Oxide .21 21 .00 Barium .15 A5 Carbonate .00
Kaolin .07 ,07 J4 .00 .75 Silica .75 .75 .00
PV53 Bentonite .13x484 = 62.92 19 Feldspar .23 x 556 = 127.88 38 Dolomite .03 x 184 = 5.52 2 Whiting .31 x 100 = 31.00 9 Zinc Oxide .21 x 81 = 17.01 5 Barium Carbonate .15 x 197 = 29.55 9 Kaolin .07 x 258 = 18.06 5 Silica .75 x 60 = 45.00 12 336.94 100
Fired to Cone 4 (1160°C) with forty-five minutes soak at top temperature this glaze was an excellent satin matt slightly opaque. All my firings are reduced. It will be seen that the above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 68
Chapter 7
RAW GLAZES FOR REDUCTION AND OXIDISED ONCE FIRED PURPOSES
The example used above is the glaze that bears my number 40.22. An explanation of the nomenclature I have used for glaze documentation is necessary, as there is no universal convention and most glaze technologists seem to develop their own systems. My original work in the Cone 4 glaze range was numbered as 4.01, 4.02 and so on. The 4 relates to the Seger or Harrison cone number 4 which melts at 1160° C.64 The early glazes were developed for use by students at the Wollongong Technical College and were designed for use on biscuited pots, that is pots that have already beenfired. Whe n I decided to pursue the present study with the glazes now designed to be "once" fired, that is to be applied on to the raw or unfired clay, I simply denoted "once" by adding the letter "O" after the cone number so the first glaze in the cone 4 range was numbered 40.01 to differentiate the two types of glaze. It is a convenient system which I have applied to the various temperature ranges at present under consideration. Once-fired glazes for 1100°C or cone 1 are numbered 10.01, cone 2 glazes are numbered 20.01, cone 3 numbered 30.01, cone 4 will be 40.01, cone 5 will be 50.01 and cone 6 will be 60.01. Many of the glazes will be clear and transparent or white and opaque and when colours in the form of oxides or stains are used or when any modification is made a note is made along with the glaze details. All my tests are numbered as they are made and not all the work results in satisfactory glazes, so in my results there may be gaps in the continuity of glaze numbers reported as I do not intend to report on the unsatisfactory ones. Of course with further work these 'discarded' tests could be developed into usable glazes. However, I have no need to pursue them at this stage as the successful ones are quite numerous and in true 'Hamada' style my work is adequate with a limited range of glazes.
6% should be noted that Seger cones which I use are numbered differendy to the American Orton cones which many potters use. 69
Part of my routine during testing has always been to paint oxide bands on the unfired glaze surfaces to test for colour response and stability for brushwork decoration. These colour bands were standardised before painting on the test pots. In addition, on some tests chromium oxide was tried, as was Leach's copper red pigment.65 For this recent research the tests resulted in the following colours:
Cobalt oxide & manganese dioxide 50/50 - medium blue Manganese dioxide - good brown Red iron oxide - pale grey green * Rutile & red iron oxide 50/50 mix - mottled brown Copper carbonate - mauve purple * Unless otherwise noted aU following references to "iron" or "iron oxide" mean red iron oxide.
In compiling this research I completed a literature search in order to assess the popularity of both mid-fire glazes and once-fired pottery. I already had a fair idea of the Australian level of studio practice so I chose the influential American journal Ceramics Monthly as an indicator of what was happening outside Australia. I carried out a detailed survey of the material published over a period of almost twenty years and during this time there seems to have evolved a greater interest in firing pots at temperatures below stoneware mainly for the reasons that I have already stated, namely the increasing costs of high firing and concern with the environment. Most of the published material covered glazes that fired at about 1200 degrees centigrade. There was little about the lower temperatures of cones 1 through to 5. It was noticable that there was an almost universal use of gerstley borate and colemanite as fluxes for lowering the temperatures from the high stoneware range. There was a great reliance on the American material Albany Slip which was modified in various ways. Between 1981 and 1994 Ceramics Monthly published some forty articles or short inclusions relating to mid-fire temperatures. Many were simply responses to requests for information from the technical staff while others dealt with the subject in greater depth. One of these was my own article Middle Fire Option.66 Others include Cone 5-6 Reduction Glazes by Paul Woolery,67 Albany Slip Clay in Oxidation Firing by Richard Zakin,68 Computer Glazes for Cone 6 Oxidation by Harold J McWhinnie,69and other as listed in the Bibliography at the end of this dissertation.
65Leach's Copper Red Pigment - Feldspar 55, Whidng 22, Silica 14, Tin oxide 3 and Copper Carbonate 2. 66Ivan Englund , Middle Fire Option, in CM, April 1985. 67Paul Woolery , Cone 5-6 Reduction Glazes in CM, April 1982 68Richard Zakin, Albany Slip Clay in Oxidation Firing in CM May 1982 69Harold J McWhinnie, Computer Glazes for Cone 6 Oxidation, in CM November 1982 70
As a more up to date survey I set up a dialogue on the Internet using Clayart. I had a range of responses which indicate a growing interest in the mid-fire range rather than a rejection, as suggested by some commentaries. A sample of the Internet responses follows:
Jeff Brett cited the inclusion of mid-firing in the syllabus of the college at which he works in Canada. He wrote:
I feel that mid-temperature ceramics has a great future. I have seen work locally and in publication that show [sic] the creative and functional potential of such work. ...I personally work in low and mid- range ceramics because of the greater color range and lower firing costs as well.70
I was encouraged to read from John Neely that:
...Englund's reputation extends beyond Australia. I have used his book on rock glazes as a resource for glaze formulation classes. ...Englund's assertion that, relative to higher and lower temperature ranges, the midfire glazes have been neglected historically, is certainly true. [However,] There are probably more people working with midfire glazes now than ever before.71
Dennis Southwood wrote:
We fire to cone 6 at Mesa College, and have for some time. I guess it started when energy costs started to rise. I don't know about other periods in history, but my impression is that the mid-range temperatures are getting pretty common now.72
Linda Arbuckle pointed me to George Bowes in Cleveland who, "works in cone 5-6, and has for some time". 73 Gloria Pollock responded, "I have been using Cone 5-6 oxidation glazes both professionally and in my classroom for 20 years."74 Suzanne Wolfe wrote, "Many studio artists in the US (Dorothy Hafner, for example, used to fire to cone 5, as did Sandy Simon...".75 There were various other references to cone 5/6 glazes.76
7fyeff Brett, in Clayart, Pub. online - North Island College, Courtenay, BC, Canada. ([email protected]), 10 August 1994 7* John Neely, in Clayart, Pub. online - Dept of Art, Utah State Uni, Logan, Utah. ([email protected]), 11 Aug 1994. ^Dennis Southwood, in Clayart, Pub. online - Mesa College, San Diego. ([email protected]), 1994. ^Linda Arbuckle, in Clayart, Pub. online - U of FI Dept of Art, Gainesville, Florida. ([email protected]), 16 Aug 94 ^Gloria Pollock, in Clayart, Pub. online - Pittsburgh, Pennsylvania, ([email protected]), 10 Aug 1994. ^Suzanne Wolfe, in Clayart, Pub. online - Uni of Hawaii, at Manoa, USA. ([email protected]), 10 August 1994. 76Claudia O'Driscoll, 'Ceramic Arts Discussion List', in Clayart, Pub. online, (claudiao@MAILHOST,CLACKAMAS.CCOR.US), 17 May 1995, Christine Winokur of Kickwheel 71
Of significance to this research, there were no responses about once firing other than one from Don Jones, who wrote, "I have built my entire business once-firing white earthenware".77 Periodic scanning of the Internet in the past few months indicates this same trend of growing interest in mid-fire glazes with only very occasional references to once firing or raw glazing.78
In the early part of my work I worked a few published formulae to recipes to see how they adjusted to the once-fire concept. This was illustrated in my detailed example of glaze number 40.22 which was based on a formula published by Parmelee79 with the "formula required" line modified to accommodate the use of bentonite in the glaze. Daniel Rhodes in his Clay and Glazes for the Potter*® published tables of possible oxide limits for cone 4 glazes but as guidelines they are only marginally useful. My long experience in pottery using the Seger formula method to evolve glazes (as far removed from each other as earthenware glazes for the Montoro Company for use on their roofing tiles and the stoneware glazes which I have created for my own use in my more than forty years as a potter) has equipped me with the knowledge necessary to readily create the formulae for original glazes. I have published two books of my original work, Middle Fire Pottery*1 and more recently Rock Glazes*2 which is used internationally by some universities in their ceramics degree courses. I have used the oxides of potassium, sodium and barium widely as they tend to favour fusion at lower temperatures more than some others. I have also used the more refractory oxide of magnesium in much greater amounts than is usually recommended, with good results. The commercial frits have been used and I have had no hesitation in using soluble materials. The alumina and silica requirements and relationships vary widely and of course I have successfully introduced my knowledge of igneous rocks to the lower temperatures of middle fired, once-fired glazes. The field of middle fire glazes is very wide and I submit that my glazes are an important further contribution to the presently available ceramic knowledge.
The glazes reported in this work were fired in three different kilns, a small 8 cu ft LP gas fired model by Port-O-Kiln, a 24 cu ft LP gas kiln of my own construction and a 35 cu ft wood-fired brick kiln. As already stated I choose to
' 'Don Jones, 'Ceramic Arts Discussion List', in Clayart, Pub. online, ([email protected]), 15 May 1995 '°As stated earlier I do not have my own computer at home. This dictated sporadic access to the Internet whenever I could use die computer attched to the Ceramics Department at the University of Wollongong. 79Warren C Parmelee. Ceramic Glazes. Cahners, NY, 1973. 80Rhodes. 81 Ivan Englund. Middle Fire Pottery. Private publication, 1967. Silvan Englund. Rock Glazes. Private publication, 1983. 72 fire with a reduced atmosphere because it enables the production of such glazes as the copper reds and the green celadons and I also like the clay colours produced by reduction. However, I also know from experience that most of the glazes in this study will fire adequately in oxidized firings and in electric kilns, although the colours will generally be more bland and celadons and copper reds are not achievable. However, oxidized celadons can be a veiy good pale amber. Leach83 gives a recipe for "Old Seto Yellow" which is really a celadon fired in oxidation. It was only when I was able to examine some Old Seto Yellow pots in Nagoya many years after reading the Leach recipe that I made this connection. While copper reds are technically not possible in an electric kiln the same copper glaze will be a very pleasant green. An alternative copper red can be achieved in an electric kiln by adding to the glaze a small amount of very fine silicon carbide which is a local reducer. Dr Lee Angel in Canberra produced these glazes for many years.
My firing schedule is as follows:
The raw-glazed pots are loaded into the kiln and then fired very slowly up to about 200°C to eliminate the water of plasticity that remains in the clay even when it is "dry". In other words the pots at this stage are treated in the same way as for a biscuit fire. After 200°C the rate of firing can be increased. I fire my gas kilns overnight with only the pilot flame burning. In the morning the temperature is always near 200°C. The fire is continued as normal to the usual biscuit temperature and then on at the same rate to the glaze maturation temperature. I usually start the reduction procedure at about 950°C. Reduction too early in the schedule may result in bloated pots and too late may mean that some colours do not develop well. I continue the reduction right to the end of the firing. When temperature is reached it is advantageous to soak for perhaps half an hour to allow the temperature in the cooler parts of the kiln to even out. After closing off the fuel I clam up the openings, spyhole and flue to allow slow cooling.
A range of raw glaze recipes follows. All are designed for once firing in the cone 1 - 6 range. The components are listed as percentages by weight. Seger formulae for most of these recipes are appended at the end of the dissertation.
8^Leach A Potter's Book. 73
Glaze No. 1O.01 Cone 1 (Seger) 1100°C
Recipe: Bentonite PV53 19 Feixo Frit 4108 41 Borax 2 Feldspar 36 Zinc Oxide 1 Silica 1
Result: A good clear glaze, crazed, dependent on the clay used. This test was on Feeney's E.
In glaze colours - Glaze plus .6% Chromium Oxide, 5% Tin Oxide The colour was a very good opaque grey green.
Glaze plus 2% Zinc Oxide, 2% Tin Oxide, 2% Titanium Oxide and 6% red Iron Oxide. This colour fired in reduction was a good solid blue. In oxidation the colour is a yellow breaking to red. 74
Glaze No. 1O.03 Cone 1 (Seger) 1100°C
Recipe: Bentonite PV53 22 Fei-ro Frit 4108 42 Feldspar 23 Barium Carbonate 4 Silica 11
Result: A very good clear glaze
Glaze No 10.03 1CH Glaze plus 1% Chromium oxide An excellent opaque bright green
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 75
Glaze No. 1O.04 Cone 1 (Seger) 1100° C
Recipe: Bentonite PV53 22 Ferro Frit 4108 39 Whiting 2 Kaolin 10 Barium Carbonate 14 Zinc Oxide 3 Silica 10
Result: A veiy good clear glaze
Glaze 10.04 4C Glaze plus 4% copper oxide. An excellent dark red with thin green rim. NOTE: This firing was reduced. With oxidation a clear green could be expected.
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 76
Glaze No. 1O.05 Cone 1 (Seger) 1100°C
Recipe: Bentonite PV53 18 Ferro Frit 4108 12 Whiting 3 Feldspar 16 Borax 23 B arium Carbonate 18 Silica 10
Result: A slighdy yellowish transparent glaze.
Colours. Having done a great deal of work with this glaze and others closely related I have made experiments with colour mostly with combinations of the usual oxides. The following list could form the basis of colours with other glazes. Obviously the materials in different glazes can vary greatly and the colour resulting from the colouring material will be affected by the differing ingredients. It should also be noted that the clay body will influence the colour.
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 77
Colour No:
1A add 2% Nickel Oxide Olive
IB add 2% Nickel Oxide 1% Copper Oxide Olive Green
1C add 2% Nickel Oxide, 1% Copper Oxide, 2% Iron OxideDark Olive
2A add .6% Cobalt oxide Transparent Blue
2B add .6% Cobalt Oxide, 2% Iron Oxide Dark Blue
3A add 1 % Copper Oxide Transparent Green
3B add 1% Copper Oxide, 2% Manganese Dioxide Transparent Dark Green
3D add 4% Copper Oxide Dark Green
3C add 1% Copper Oxide, 2 Manganese Dioxide, 2 Red Iron Oxide Bottle Green
6B add 6% Iron Oxide, 6 Rutile Dark Green
6C add 6 % Iron Oxide, 6 Rutile, 6 Zircon Flour Ochre Yellow
11B add 2% Manganese Dioxide Medium brown
11G add 6% Manganese Dioxide Brown
11F add 4% Manganese Dioxide, 4 Iron Oxide Dark Brown
12c add 2%Iron Oxide Transparent Dark Brown
13d add 10% Dolomite Creamy Opaque
13e add 6% Dolomite, 1% Copper Oxide Grass Green
13f add 6% Dolomite, 6% Manganese Dioxide Coffee Brown
14a add 6% Zircon Opacifier Grade Off White semi opaque
15a add 4% Zinc Oxide, 4% Tin Oxide, 4% Titanium Oxide Satin White Opaque
15e add the above (15a) plus 6% Cobalt Oxide Pale Blue
15f add 2% Zinc, 2% Tin, 2% Titanium, 6% Iron Oxide Dark Orange Red 78
17b add .6% Chromium Oxide, 6% Tin Oxide Grey Green
18a add 3% Chromium Oxide, .3% Copper, 5%Silica Bright Green
19b add .5% Cobalt Oxide, .16% Nickel Oxide, .6% Whiting, 3% Zn Oxide Pale Opaque Blue
20a add 2.76% Chromium Oxide, .33% Cobalt Oxide Opaque Bright Green
21b add .33 Chromium Oxide, 1 Cobalt Oxide, 3 Alumina, 6 Zircon Blue
22a add 2.5% Kaolin, .8% Chromium Oxide, 18% Whiting Bright Green
23a add 1% Chromium Oxide, 2% Zinc, 1% Silica Opaque Green
24b add .25% Chromium Oxide, 2% Tin Oxide, 1% Whiting, 15% Borax Green
26b add . 15% Cobalt Oxide, 3% Alumina, .6% Zinc Oxide Pale Blue
38b add 6% Blythes Yellow Stain No. 235, 6% Zircon Yellow
39b add 6% Blythes Pink Stain No. 204, 6% Zircon Pink
41b add 6% Blythes Turquoise Stain No. 110, 6% Zircon Opaque Blue
42b add 6% Blythes Coral Stain No. 200, 6% Zircon Brown Coral
44b add 6% Blythes Light Green Stain No. 193, 6% Zircon Opaque Pale Green
45b add 6% Blythes Green Stain No. 648, 6% Zircon Green
Apart from the differences in colour that can result from different glazes and differing clays the kiln atmosphere can affect colour especially those with small amounts of copper and iron. With copper in oxidation the colour will normally be green while in reduction the colour can be some variation of red, the so called "copper red". A small amount of iron oxide in the glaze will be amber in oxidation and green or grey green in reduction. The best of this colour could be "celadon". Glaze No. 2O.01 Cone 2 (Seger) 1120°C
Recipe: Bentonite PV53 21 Ferro Frit 4108 30 Feldspar 24 Whiting 4 Zinc Oxide 7 Silica 14
Result: A good clear glaze.
Glaze 11.01 19B Glaze plus .5% CoO, .16% NiO, 3% ZnO. Opaque grey blue rather matt. 30.06 Cone 3 (Seger) 1136°C
Semi Opaque
32 Bentonite PV53 Ferro Frit 4108 40 Dolomite 10 Zinc Oxide 8 Whiting 7 Alumina 3
A good grey green slightly milky glaze. Copper carbonate brushwork can be a bright red. 81
Glaze No 30.07 Cone 3 (Seger) 1136°C
Opaque Soft Grey
Recipe: Bentonite PV53 27 Ferro Frit 4108 52 Feldspar 10 Dolomite 6 Whiting 5
Result The glaze on white clay was a very good opaque soft grey tending slightly greenish. Oxide brush marks painted on the glaze all bled but gave good blue with cobalt and manganese mixed, a sharp interesting brown with manganese while copper carbonate gave a dark grey green. On a local clay which fires off white to pale buff the glaze was a good greenish matt with opalescence in the more heavily glazed areas. The glaze proved to be a good vehicle for coloured glazes. With .5% CoO and 1% Mn02 (numbered 3O.07B) the colour was an opaque pale blue.
The most unusual colour combination tested was the addition of .5% CuC03 and 2% Sn02 which in some glazes is the basis for copper reds so the glaze number is 30.07 C R. However copper red in the true sense was absent but in three firings with slightly differing temperatures and with different setting combinations of densely packed and lightly packed excellent variations were achieved. In the coolest part of the kiln the glaze was an excellent opaque duck egg blue green speckled with purple red throughout. In the kiln centre where the temperature was a genuine cone 3 the colour was a very smooth all over delicately mottled pinkish mauve. In the hottest place the glaze ran (but not over the foot) and became a really good flam be with typical copper red, opalescent and blue streaks. At the top of the pot (again a bit hotter) the colour was the usual greenish grey with small patches of red which is usual with flambe. It seems this glaze could well be fired a cone lower at about 1120°-1130OC. No. 30.08 Cone 3 1136°C
Opaque Semi Matt White
Feiro Frit 4108 51 Silica 19 Whiting 14 Bentonite PV53 16 Zircon OP (opacity grade) 6 Tin Oxide 4
Excellent opaque white glaze. The zircon andtin need to be ground together in a mortar with a drop of water before being added to the glaze, otherwise the glaze will be full of white spots.
Adding .5% CoO and 1% Mn02 will result in a pale blue (number 30.08B) while the usual oxides for copper red, .3% CuC03 and 2% Sn02 will result in a most unusual matt flambe colour. 83
Glaze No. 30.11 Cone 3 (Seger) 1136°C
Recipe: Bentonite PV53 16 Barium Carbonate 4 Zinc Oxide 1 Ferro Frit 4113 71 Silica 9
Result: A very good opalescent blue especially when applied over black or dark terracotta slip. The blue colour can be enhanced with the addition of up to .5% of either cobalt oxide or copper oxide.
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. Glaze No. 30.13 Cone 3 (Seger) 1136°C (NOTE: Same glaze as 40.13 lower fired)
Recipe: Bentonite PV53 15 Ferro Frit 4108 22 Ferro Frit 4113 22 Feldspar 31 Zinc Oxide 10
Result: Very good opalescent jun.
Glaze 30.13 CS Glaze plus .5% copper slag. A most unusual effect with the slag evenly distributed as spots and patches of green, bluegreen, red and metallic black in a body glaze of cream.
Glaze 30.13 B Glaze plus 1% CoO 2% Mn02 Excellent brilliant blue with faint mottle. CuC03 brushing was varied green and red. 85
Glaze No 30.13CS 86
Glaze No. 30.47 Cone 3 (Seger) 1136°C
Bumbo Latite Celadon
Recipe: Bentonite PV53 24 Bumbo Latite 12 Feiro Frit 4108 39 Whiting 2 Barium Carbonate 15 Silica 3
Result: Fired in reduction this glaze proved to be a grey green or yellow green celadon depending on whether it was applied to a white or dark clay. Usually it was crazed in a small pattern. Trailed patterns of opaque glaze number 30.08 OP and blue number 30.08B provided veiy good contrasts. In my stoneware work I had had success in using an igneous rock glaze utilising the Moonbi Granite near Tamworth to produce a celadon which I then converted to a copper red by the addition of the usual oxides, .3% CuC03 and 2% Sn02- As this Bumbo Latite glaze was also a celadon having only .02 molecular parts of iron oxide from the rock in its composition I prepared a test for a possible copper red. Fired at 1136° C in reduction it proved to be a superior copper red glaze with very good coverage.
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 87
Glaze No 30.47 Glaze No. 30.48 Cone 3 (Seger) 1136° C
Walcha Basalt Glaze NOTE: Suitable for all basalts
Recipe: Bentonite PV 53 24 Walcha Basalt 16 Feiro Frit 4108 40 Barium Carbonate 17 Silica 3
Result: A very good soft grey with some speckle.
Glaze 30.48 F Glaze plus 10% Fe203 An excellent dark iron glaze with some iridescence and varied tea dust, browns and blues.
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. Glaze No. 30.54 Cone 3 (Seger) 1136°C NOTE: Glaze 40.54 lower fired
Recipe: Bentonite PV 53 17 Ferro Frit 4108 43 Feldspar 33 Kaolin 5 Silica 2
Result: Glaze. 30.54 1R Glaze plus 4% Fe203, 4% Rutile. Very good matt grey blue with pale yellowish spots.
Glaze. 30.54 BB Glaze plus 2% CuO, 2% Ilmenite .5% CoO. Excellent matt green/blue/yellow. Glaze No. 40.02 Cone 4 (Seger) 1160°C
Matt Grey
Recipe: Ferro Frit 4108 40 Wood Ash 45 Bentonite PV53 15
Result: Reserved matt grey which flowed slightly.
Oxide Colour Bands: All colours flowed badly on this glaze but where broken colour could be tolerated for its own sake the mixed blue of CoO and Mn02, manganese and probably rutile could be useful as well as Leach's Cu pigment.
Note: Glaze Composition Because wood ash is very variable in chemical composition it does not allow itself to be used in the Seger Formula. It could be analysed but that is an unnecessary expense. So a recipe such as the above is purely empirical, one could almost say "seat of the pants" informed guesswork. In histoiy, for hundreds and perhaps thousands of years potters evolved glazes in this manner. Try something, evaluate and adjust it. 91
Glaze No. 40.04 Cone 4 (Seger) 1160°C
Clear
Recipe: Bentonite PV 53 14 Nepheline Syenite 38 Zinc Oxide 7 Lithium Carbonate 3 Whiting 10 Silica 28
Result: The glaze is a very good clear glaze just off white.
Oxide Colour Bands: CoO plus Mn02 - strong vibrant blue Mn02 - coffee brown Fe203 - grey green Fe203/rutile mix - opaque dark brown CuC03 - dull purple Chrome oxide - opaque green brown 92
Glaze No. 40.07 Cone 4 (Seger) 1160°C
Basalt Glaze
Bentonite PV 53 15 Basalt 40 Barium Carbonate 11 Zinc Oxide 4 Dolomite 4 Whiting 8 Lithium Carbonate 2 Silica 16
Results: (with various igneous rocks)
No. 40.07 J with Walcha Basalt [John Leah Quarry]. Excellent matt yellow green Iron brushwork - good brown
No. 40.07 B. with Bumbo Latite near Wollongong. Excellent deep green. Iron brushwork - good varied browns.
No. 40.07 R. with Raymond Terrace Dacite. Very good speckled grey green. Iron brushwork - dull brown. 93
Glaze No. 40.08 Cone 4 (Seger) 1160°C
Frit Glaze
Recipe: Bentonite PV 53 25 Ferro Frit 4108 54 Whiting 10 Kaolin 11
Result: Clear with tiny amount of opalescence.
Oxide Colour Bands: CoO plus Mn02 - grey blue Mn02 - transparent brown Fe203/Rutile mix- good ciystal kaki brown Chrome oxide - good green 94
Glaze No. 40.09 Cone 4 (Seger) 1160° C
Satin Matt
Recipe: Bentonite PV 53 16 Nepheline Syenite 44 Zinc Oxide 7 Barium Carbonate 9 Whiting 8 Silica 16
Result: Excellent satin matt with an almost crystaline surface.
Colour is a pale grey on white clay. On a dark clay the colour a darker grey due to the clay colour showing through.
Oxide Colour Bands CoO plus Mn02 - good bright blue Mn02 - dark brown Fe203/rutile mix - crystaline brown CuC03 - dull brown red
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 95
Further glaze colours: No. 40.09 BK Add 1% C@0, 4% Fe203, 4% Mn02 Excellent semi matt brownish black with a silvery surface.
No. 40.09 CR Add .3% CuC03, 2% S11O2 Excellent matt copper red. The red is more towards a sealing wax red. The surface exhibits the same silvery surface as all the above. This glaze would improve if fired to a higher temperature.
No. 40.09 B Add 1% CoO, 2% M11O2. Very good matt royal blue. A smaller amount of colour oxides could result in a more pleasant blue.
No. 40.09 CC Add .5% CoO, 2% CuO. Matt dull blue.
No. 40.09 F Add 8% Fe203. Excellent semi matt dark green breaking to brown on the rims.
No. 40.09 Y Add 6% Blythes Yellow Stain 235, 6% Zircon flour. Excellent semi matt. Colour just a tinge of yellow. 96
Glaze No. 4O.10 Cone 4 (Seger) 1160°C
Opalescent
Recipe: Bentonite PV 53 15 Borax 34 Whiting 9 Magnesium Carbonate 2 Feldspar 13 Kaolin 6 Silica 22
Result: Clear with opalescence in thickly glazed areas.
Oxide Colour bands: CoO plus Mn02 - good medium blue Mn02 - good brown Fe203 - pale blue green CuC03 - dark purple red 97
Glaze No. 40.11 Cone 4 (Seger) 1160°C
Shiny Opaque
Recipe: Bentonite PV 53 20 Feldspar 48 Whiting 9 Zinc Oxide 10 Silica 13
Result: A beautiful opaque shiny glaze very nearly white. With some of these "Once-fire" glazes occasionally there will be a slight flake off at the edges. Simply touch up any such areas with a brush when diy.
Oxide Colour Bands: CoO plus Mn02 - blue black Mn02 - matt coffee brown Fe203 - yellow green Fe203/Rutile mix- opaque coffee brown CuC03 - metallic brown-red halo Glaze No. 40.13 Cone 4 (Seger) 1160°C
This recipe is based on the calculations in Glaze No. 40.54.
Recipe: PV 53 15 Ferro Frit 4108 22 Ferro Frit 4113 22 Feldspar 31 Zinc Oxide 10
Result: Excellent rich opalescent blue
Oxide Bands: Cobalt &Manganese - good medium blue Manganese - varied yellow to brown Copper Carbonate - mottled red
All oxides bled into the glaze but the colour results indicate that the glaze would be an excellent vehicle for most colours. 99
Glaze No 40.13 100
Glaze No. 40.22 Cone 4 (Seger) 1160°C
Satin Matt Opaque Celadon
Recipe: Bentonite PV53 19 Feldspar 38 Dolomite 2 Whiting 9 Zinc Oxide 5 Barium Carbonate 9 Kaolin 5 Silica 13
Result: The glaze is an excellent Satin Matt opaque celadon green.
Oxide Colour Bands: CoO plus Mn02 - excellent blue Mn02 - good brown Fe203 - pale grey green Fe203 plus Rutile- good speckled brown CoO - dull purple
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 101
Glaze No 40.22 102
Glaze No. 40.23 Cone 4 (Seger) 1160°C
Blue green celadon
Recipe: Bentonite PV 53 19 Soda Ash 22 Feldspar 10 Whiting 8 Barium Carbonate 24 Silica 17
Result: The glaze is an excellent bluish green celadon of excellent quality.
Oxide Colour Bands: CoO & Mn02 rich dark blue Mn02 dark purple brown Fe203 pale blue Fe203 Plus Rutile- green to brown CuC03 good purple red Leach Cu Red pigment- ex.copper red
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 103
'
*
Glaze No 40.23CR 104
Glaze No. 40.24 Cone 4 (Seger) 1160°C
Opaque
Recipe: Bentonite PV 53 18 Feldspar 32 Dolomite 3 Borax 10 Whiting 15 Kaolin 9 Silica 13
Result: A very smooth, slightl y greenish opaque matt.
Oxide Colour Bands: CoO plus Mn02 - very dark blue Mn02 yellow brown Fe203 pale grey green Fe203/rutile mix - very dark brown C0CO3 pale grey purple 105
Glaze No. 40.25 Cone 4 (Seger) 1160°C
Recipe: Bentonite PV 53 16 Feldspar 34 Borax 23 Whiting 11 Silica 16
Result: Good transparent tending towards pale green
Oxide Colour Bands: CoO plus Mn02 - strong inky blue Mn02 dark brown Fe203 olive green Fe203/rutile mix - dark brown CuC03 dark purple red Leach Cu red pigment- dark purple red Chrome oxide - yellow green 106
Glaze No. 40.26 Cone 4 (Seger) 1160°C
Clear
Recipe: Bentonite PV53 21 Feldspar 11 Borax 32 Lithium Carbonate 2 Whiting 11 Zinc Oxide 6 Silica 17
Result: Good clear glaze with some opalescence in thickly glazed areas.
Oxide Colour bands: CoO plus Mn02 - good blue which bled badly Mn02 - coffee brown Fe203 - grey green CuC03 - varied green to red Leach Cu pigment- excellent copper red 107
Glaze No. 40.28 Cone 4 (Seger) 116QOC
Opaque Matt
Recipe: Bentonite PV53 19 Feldspar 23 Dolomite 7 Borax 10 Whiting 11 Barium Carbonate 6 Silica 24
Result: Very good reserved matt slightly blue. The glaze did not heal over slight imperfections. Perhaps it could be fired to a higher temperature.
Oxide Colour Bands: CoO plus Mn02 good matt purplish blue Mn02 yellow brown Fe203 grey green Rutile almost black brown C0CO3 dull green
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 108
Glaze No. 40.32 Cone 4 (Seger) 1160°C
Clear
Recipe: Bentonite PV53 18 Borax 21 Whiting 13 Barium Carbonate 17 Kaolin 9 Silica 22
Result: A good transparent clear glaze tending towards pale green because of the reduced firing.
Oxide Colour Bands: CoO plus Mn02 - strong dark blue Mn02 - strong brown Fe203 - olive green Fe203/rutile mix - crystal brown CuC03 - dull metallic brown red
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 109
Glaze No. 40.33 Cone 4 (Seger) 1160°C
Clear
Recipe: Bentonite PV53 18 Borax 23 Podmore Frit P2244 5 Zinc Oxide 4 Whiting 9 Kaolin 11 Silica 30
Result: Very good clear tending grey green.
Oxide Colour Bands: CoO plus Mn02 -good medium blue which bled Mn02 - sharp brown Fe203 - grey green Fe203/Rutile mix- crystaline brown CuC03 - dark purple red Leach Cu red pigment- good copper red 110
Glaze No. 40.34 Cone 4 (Seger) 1160°C
Clear
Recipe: Bentonite PV 53 16 Borax 24 Podmore Frit P2244 5 Barium Carbonate 8 Dolomite 4 Zinc Oxide 2 Whiting 6 Kaolin 14 Silica 21
Result: Very good clear glaze tending towards greyish celadon.
Oxide Colour Bands: CoO plus Mn02 - dark blue, slight bleeding Mn02 dark brown Fe203 pale grey green Fe203 plus rutile - dark speckled browns CuC03 metallic dark red
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. Ill
Glaze No. 40.38 Cone 4 (Seger) 1160°C
Matt
Recipe: Bentonite PV53 21 Nepheline Syenite 28 Feldspar 20 Whiting 20 Barium Carbonate 2 Silica 9
Result: Excellent satin matt.
Oxide Colour Bands: CoO plus Mn02 - strong vibrant blue Mn02 dark brown Fe203 pale green Fe203/rutile mix - varied browns CuC03 varied red Leach Cu red pigment- clear pink red
Cr203 grey-brown
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 112
Glaze No. 40.39 Cone 4 (Seger) 1160°C
Matt
Recipe: Bentonite PV53 25 Whiting 28 Lithium Carbonate 7 Kaolin 22 Silica 18
Result: Good matt glaze.
Oxide Colour Bands: CoO plus Mn02 - medium blue Mn02 medium brown Fe203/rutile veiy rough surface CuC03 copper green Leach Cu pigment- good pink Chrome oxide brown black 113
Glaze No. 40.51 Cone 4 (Seger) 116QOC
Semi Matt
Recipe: Bentonite PV53 21 Nepheline Syenite 40 Whiting 6 Zinc Oxide 8 Barium Carbonate 12 Silica 13
Result: Excellent smooth semi matt tending towards blue green.
Oxide Colour Bands: CoO plus Mn02 - bright medium blue Mn02 pale beige Fe203 good grey green Fe203/rutile mix - dull matt brown Q1CO3 copper red Leach Cu pigment- matt copper red
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 114
Glaze No. 40.52 Cone 4 (Seger) 1160°C
Raymond Terrace Dacite Glaze
Recipe: Bentonite PV 53 20 Raymond Terrace Dacite 20 Whiting 15 Borax 24 Barium Carbonate 9 Silica 12
Result: The glaze was a medium yellow green transparent colour which flowed though it stopped short of the foot.
Colour Oxide Bands: All flowed badly mling out oxide brushwork decoration.
CoO plus Mn02 - good medium blue Mn02 - medium brown Fe203 - grey green Fe203/rutile mix - dark brown CuC03 - very good varied copper red
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 115
Glaze No. 40.53 Cone 4 (Seger) 1160°C
Jun Blue
Recipe: Bentonite PV53 16 Feldspar 34 Borax 23 Whiting 11 Silica 15
Result: This glaze resul next No. 40.54. Refer to earlier notes regarding my use of soluble materials.
Colour No. 40.53 BB (Beryl's Blue) add 2% CuO, 2% Ilmenite and .5% CoO
The oxide combination in this glaze results in a varied mottled green/blue/ochre depending on the thickness of glaze application. 116
Glaze No. 40.54 Cone 4 (Seger) 1160°C
Jun-like Blue
Recipe: Bentonite PV 53 18 Feiro Frit 4108 42 Feldspar 32 Kaolin 56 Silica 2
This glaze is another version of the previous one No. 40.53 for they have virtually the same molecular formula. The difference is that the soluble borax is eliminated and Ferro Frit 4108 substituted to overcome the fears and prejudices of some potters.
Result: The glaze is always a jun-like blue which while satisfactory on white clay is more spectacular over dark clay or black slip. The blue is not quite as strong as in No. 40.53. The borax ingredient seems to favour the formation of the blue more than does the frit. The tiniest amount of CoC03 added will add to the solidity of the blue colour but tends to degrade the opalescence of the chun effect. The addition of my favourite mixture of oxides: 2% CuO, 2% Ilmenite and .5 CoO% will result in a spectacular mottled or speckled colour of blues, greys, yellow, greens and red. A painter friend likened the mixed colours to the effects of the pointillist painters of the post impressionist period. 117
Glaze No 40.54 No. 50.01 Cone 5 (Seger) 118Q0C
Bentonite PV 53 19 Feldspar 58 Zinc Oxide 6 Whiting 10 Silica 7
The glaze is an excellent semi-matt tending towards a blue celadon. Non crazed on Clayworks SWE Clay and Feeney E.
Bands: Cobalt/manganese mix - excellent dark blue. Fe203 -a good yellowish brown CuC03 - an opaque pink red 119
Glaze No 50.01 120
Glaze No. 50.02 Cone 5 (Seger) 1180°C
Recipe Bentonite PV 53 24 Feldspar 48 Zinc Oxide 8 Whiting 17 Kaolin 3
Result: A reserved stony matt opaque glaze.
Colour Band: The blue was a strong dark colour. 121
Glaze No. 50.07 Cone 5 (Seger) 1180°C
Recipe: Bentonite PV53 14 Feldspar 18 Whiting 12 Lithium Carbonate 14 Kaolin 20 Silica 22
Result: A very good semi-matt opaque on SWE clay and a solid grey matt on Feeney E. 122
Glaze No. 5O.10 Cone 5 (Seger) 1180C
Recipe: Bentonite PV 53 17 Whiting 13 Barium Carbonate 4 Feldspar 55 Silica 11
Result: Excellent smooth, uncrazed opaque on SWE clay and smooth grey on Feeney E.
Colour Bands: Blue very nice blue Iron Oxide yellow brown CuC03 good pink red
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 123
Glaze No. 50.11 Cone 5 (Seger) 1180°C
Recipe: Bentonite PV 53 23 Feldspar 35 Whiting 7 Barium Carbonate 15 Zinc Oxide 12 Silica 8
Result: The glaze is a good semi-matt which combines well with blue pigments.
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 124
Glaze No. 50.12 Cone 5 (Seger) 1180°C
Recipe: Bentonite PV 53 23 Whiting 7 Barium Carbonate 22 Zinc Oxide 8 Kaolin 17 Silica 23
Result: I have a personal dislike for so-called "dry" glazes i.e. glazes which either haven't melted or are overloaded with one or other of the oxides. To me glaze means melted. However, the above glaze while being a "dry" glaze has quite a pleasant matt surface. A warning is often given that such glazes should not be used for food containers. In any case the rough surface is quite unsuitable for such use. This glaze would be useful on sculptural pieces.
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 125
Glaze No. 60.02 Cone 6 (Seger) 1200°C Matt
Recipe: Bentonite PV 53 18 Feldspar 58 Whiting 10 Barium Carbonate 11 Silica 3
Result: This glaze is a very good opaque semi matt.
Oxide Colour Bands: CoO plus Mn02 good medium blue Mn02 beige to brown Fe203 pale green to grey olive Fe203/rutile mix dull brown CuC03 matt purple pink
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 126
Glaze No. 60.05 Cone 6 (Seger) 1200°C
Smooth Celadon
Recipe: Bentonite PV53 17 Dolomite 3 Feldspar 30 Borax 5 Whiting 16 Kaolin 5 Silica 25
Result: Excellent smooth greyish celadon on dark clay.
Oxide Colour Bands: CoO plus Mn02 good dark blue Mn02 coffee brown Fe203 grey green CuC03 dull greyish purple red 127
Some colours:
No. 60.05 F10 Glaze plus 10% Fe203 excellent green and brown tea dust.
No. 60.05 F4 Glaze plus 4% Fe203 is a very good smooth matt green.
No. 60.05 OP Glaze plus 4% Zircon flour, 4% Tin Oxide smooth pale beige.
No. 60.05 CMR Glaze plus 5% CoO, 1% Mn02, 2% Rutile transparent dark grey blue. 128
Glaze No. 60.09 Cone 6 (Seger) 1200°C
Semi Matt
Recipe: Bentonite PV 53 20 Dolomite 9 Feldspar 39 Whiting 9 Barium Carbonate 8 Silica 15
Result: The glaze is an excellent smooth off white.
Oxide Colour Bands: CoO plus Mn02 green medium blue Mn02 coffee brown Fe203 olive green Fe203/rutile mix olive green CuC03 good mauve pink
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 129
Glaze No. 60.11 Cone 6 (Seger) 1200°C
Smooth off White
Recipe: Bentonite PV 53 22 Feldspar 47 Whiting 4 Barium Carbonate 15 Zinc Oxide 11 Silica 1
Result: A good smooth off white. Non crazed but that would depend on the clay used.
Colour Response:Oxide bands painted on unfired glaze. Co0+Mn02 - blue, very good medium to dark blue Mn02 - brown Fe203 - olive Rutile - brown CuCo3 - purple red Ci"203 - olive brown
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 130
Glaze 60.12 Cone 6 (Seger) 1200°C
Opaque White
Recipe: Bentonite PV 53 21 Feldspar 31 Zinc Oxide 26 Silica 22
Result: Very good reserved opaque white.
Oxide Colour Bands: CoO plus Mn02 -strong purple blue tending to flow Mn02 - coffee brown Fe203 - pale green Fe203/rutile mix - crystal brown CuC03 - brown red Leach Cu pigment- pink Glaze No. 60.14 Cone 6 (Seger) 1200°C
Clear
Recipe: Bentonite PV 53 20 Feiro Frit 410 8 8 Feldspar 44 Whiting 18 Kaolin 2 Silica 8
Result: A good transparent clear tending towards yellow g
Oxide Colour Bands: CoO plus Mn02 - strong blue Mn02 dark chocolate Fe203 pale green Fe203/rutile mix - olive CuC03 good purple red Leach Cu red pigment- excellent red Chrome good olive green 132
Glaze No 60.14 133
Glaze No. 60.15 Cone 6 (Seger) 1200°C
Pale greyish celadon
Recipe: Bentonite PV53 19 Feiro Frit 4108 8 Feldspar 38 Barium Carbonate 2 Silica 17 Whiting 16
Result: An excellent smooth pale slightly greyish celadon.
Oxide Colour Bands: CoO plus Mn02 - very dark blue Mn02 - shaip brown Fe203 - pale green Rutile & iron - dark olive CuO - good pink red
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 134
Glaze No 60.15 Glaze No. 60.18 Cone 6 (Seger) 1200°C
Clear
Recipe: Bentonite PV 53 22 Nepheline Syenite 31 Whiting 16 Barium Carbonate 14 Lithium Carbonate 4 Silica 11
Result: A clear off white glaze.
Oxide Colour Bands: CoO plus Mn02 - pleasant blue bled badly Mn02 - brown which bled badly
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 136
Glaze No. 60.21 Cone 6 (Seger) 1200°C
Opaque
Recipe: Bentonite PV 53 19 Feldspar 66 Whiting 6 Zinc Oxide 9
Result: A very reserved opaque glaze.
Oxide Colour Bands: CoO plus Mn02 veiy dark inky blue Mn02 -brown Fe203 pale brown Fe203/rutile mix matt chocolate brown 137
Glaze No. 60.22 Cone 6 (Seger) 1200°C
Granite Celadon
Recipe: Bentonite PV 53 18 Granite dust 40 Barium Carbonate 11 Whiting 14 Silica 17
Result: This glaze was a very good slightly speckled green. The granite was sieved through on 80 mesh sieve (.0071 mm). With ball milling to afiner material the specks would be eliminated. With the addition of 10% Fe203 the glaze became an iron black. Fine grinding of the glaze was necessary.
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 138
Glaze No. 60.25 Cone 6 (Seger) 1200°C
Opaque Semi Matt
Recipe: Bentonite PV 53 22 Feldspar 27 Dolomite 7 Whiting 15 Zinc Oxide 4 Silica 25
Result: Very good reserved semi matt glaze.
Oxide Colour Bands: CoO plus Mn02 - quiet grey blue Mn02 - medium brown Fe203 - grey green Fe203/rutile mix - olive to brown 139
Glaze No. 60.26 Cone 6 (Seger) 1200°C
Matt
Recipe: Bentonite PV 53 22 Soda Feldspar 57 Whiting 13 Soda Ash 4 Zinc Oxide 4
Result: Excellent matt glaze.
Oxide Colour Bands: CoO plus Mn02 - matt mid-blue Mn02 - brown Fe203 - olive grey CuC03 - copper pink 140
Glaze No. 60.27 Cone 6 (Seger) 1200°C
Opaque semi-matt
Recipe: Bentonite PV 53 18 Feldspar 58 Soda Ash 3 Whiting 8 B arium Carbonate 11 Silica 2
Result: Very good opaque semi matt.
Oxide Colour Bands: CoO plus Mn02 - strong opaque blue Fe203 - olive grey green CuC03 - pink red
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 141
Glaze No 60.27 142
Glaze No. 60.28 Cone (Seger) 1200°C
Average Basalt Glaze
Recipe: Bentonite PV 53 20 Average basalt 44 Whiting 4 Barium Carbonate 3 Zinc Oxide 16
Result: This glaze was developed to use any basalt where the analysis was unknown or unavailable. The glaze is suitable for other igneous rocks as well.
No. 60.28 R Raymond Terrace Dacite. Off white almost clear.
No. 60.28 B Bumbo Latite. Veiy good smooth olive green.
No. 60.28 W Walcha Basalt Excellent almost black olive turning yellow where thin
No. 60.28 Gl Glen Innes Basalt Excellent dark crystalline brown, yellow where thin
No 60.28 GS Mr Gibraltar Syenite Dark mottled with green
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 143
Glaze No. 60.29 Cone 6 (Seger) 1200°C
Clear
Recipe: Bentonite PV53 13 Frit P2244 24 Feldspar 23 Magnesium Carbonate 4 Kaolin 9 Silica 27
Result: A good semi transparent glaze tending towards.yellow green.
Oxide Colour Bands: CoO plus Mn02 - blue black Mn02 purple brown Fe203 pale brown Fe203/rutile mix - matt dark brown CuC03 brown red Leach Cu red pigment- brown red Chrome oxide - unmelted green 144
Glaze No. 60.30 Cone 4 (Seger) 1160°C
Clear
Recipe: Bentonite PV 53 17 Borax 21 Whiting 14 Barium Carbonate 17 Kaolin 9 Silica 22
Result: Very good clear glaze tending towards celadon.
Oxide Colour Bands: CoO plus Mn02 -intense inky blue which bled slightly Mn02 - dark coffee brown Fe203 - green brown Fe203/rutile mix - crystal brown CuC03 - metallic purple brown
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 145
Glaze No. 60.44 Cone 6 (Seger) 1200°C
Clear
Recipe: Bentonite PV 53 17 Feldspar 31 Dolomite 3 Whiting 18 Kaolin 5 Silica 26
Result: A good white semi matt.
Oxide Colour Bands: CoO plus Mn02i!i- strong blue black Mn02 brown Fe203 pale green Fe203/rutile mix - strong brown
CuC03 pale mauve 146
Glaze No. 60.60 Cone 6 (Seger) 120QOC
Recipe: Bentonite PV 53 21 Feldspar 26 Dolomite 1 Talc 19 Borax 12 Zinc Oxide 15 Kaolin 5 Silica 1
Resuk: A good shiny opaque glaze the colour of which in my test was a beige-brown from the iron picked up from the Feeney E clay. 147
Glaze No. 60.61 Cone 6 (Seger) 1200°C
Recipe: Bentonite PV 53 20 Ferro Frit 4108 15 Feldspar 38 Whiting 19 Silica 7
Result: Good clear grey green. The green colour probably results from iron pickup from Feeney E clay. 148
Glaze No. 60.62 Cone 6 (Seger) 1200°C
Recipe: Bentonite PV 53 120 Feldspar 37 Talc 18 Zinc Oxide 17 Lithium Carbonate 1 Kaolin 3 Silica 5
Result: Excellent smooth opaque white. No. 60.63 Cone 6 (Seger) 1200°C
Bentonite PV 53 24 Ferro Frit 4108 50 Magnesium Carbonate 9 Kaolin 17
A very good clear to pale green glaze. The green is due to the pick up of iron oxide from the Feeney E clay. 150
Glaze No. 60.65 Cone 6 (Seger) 1200°C
Bentonite PV 53 14 Feiro Frit 4108 3 Dolomite 1 Feldspar 35 Borax 6 Barium Carbonate 5 Whiting 13 Silica 23
Result: The glaze was an excellent clear tending towards celadon because of the pick up of iron from the Feeney E Clay.
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. 151
Glaze No. 60.66 Cone 6 (Seger) 1200OC
Recipe: Bentonite PV 53 16 Whiting 12 Feldspar 30 Barium Carbonate 16 Zinc Oxide 2 Silica 24
Result: This glaze is a superior opaque pale green the opacity resulting in part to myriads of tiny enclosed bubbles. The celadon like green occurs through the solution of iron oxide from the surface of the Feeney E Clay
Warning: The above glaze contains barium carbonate which is a poison and should be handled very carefully. It is advisable to use gloves and face masks when handling the dry material. BIBLIOGRAPHY
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Yanagi, Soetsu. The Unknown Craftsman. Kodansha, Tokyo, 1972. 00 X o Q +-> O OH u CM © S3 o r» co CO OO © 3 ro o o CM *-J n CO o CM <->| O CO q« CM o CO o CM a rM rr flO oo ^r o o o ©rr C S3 CM CM © H (S « H Hi O o 3 o 8« ro © O i—i) oo ool cd not tf C7\ t> »0 OO 3.0 0 4.8 0 6.7 6 vo ^ ^H o CM II II II II || || rf ^O CN VO __ _, —'I O oo «n OO lO ,3(5 yo CM CM O Tt m co m °° ^ X X X X X X COONH(SOO o ^ r-~ o CM © o CM n Z H -st CMl CM CMl O CM OJ CM CMJO O O o ro >/-) oo ex. O > CO o *—> T3 O 3 o U £ a cd o o 2x -sr^ o^ CO O cs .-i CM 00 n a; 0) —i r- o CM ,-; o PP tin fflfcNo u .£ o n CO oo > o (U cd "3 ^- Us i. 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In this study I have used several commercially available clays as well as my own traditionally prepared bodies. In the early stages of this research I used my stoneware clay, Walkers PB103. This was reasonably successful at the higher temperatures in my study but was too porous in my opinion at the lower. I then used Clayworks SWE as a near white body and Feeney's E as a darker clay both proving very satisfactory, easily thrown and satisfactory in the kiln. My own personally prepared clay was very good also but it is based on a local material not generally available. However, I did make many tests of clay bodies mixed from milled materials and which were successful at the "middle" temperatures of this study. These are easily prepared. Body 1 This is a near white body, quite plastic with small shrinkage. Kaolin 20 Silica 35 Ball Clay 30 Nepheline Syenite 15 Body 2 An excellent wheel clay. Fires water tight at Cone 4 but can be fired to stoneware. Kaolin 31 Ball Clay 31 Nepheline Syenite 25 Silica 13 Body 3 A white plastic body, non porous at Cone 4 and above. Ball Clay 50 Silica 17 Feldspar 33 Body 4 Good throwing body. Its whiteness depends on the choice of both kaolin and ball clay, non porous at Cone 4. Kaolin 35 Ball Clay 20 Silica 25 Nepheline Syenite 20 Body 5 A good throwing clay which fires well at Cone 4 and is coloured by the red clay. Kaolin 27 Ball Clay 9 Silica 23 Nepheline Syenite 18 Red Clay 23 APPENDIX 3 The Exhibition BLOOMFIELD The Bkxxiifielcl Galleries GALLERIES - NEWS! NEWS! NEWS! Lin has returned from her trip to France and Spain filled with enthusiasm for Australian art today. "Even though our artists suffer from the tyranny of distance and consequent lack of access to major museums, they are right up there when it comes to expertise In painting and sculpture across a broad spectrum of subject matter and our commercial galleries compare very favourably with those I saw", she says. Highlights of the trip were the Matisse exhibition at Georges Pompidou, the Titian and Amenoteph III at the Petit Palais and the Zadklne at the Musee Zadkine In Paris; the Prado, Museum of Contemporary Art and the new Thyssen Bornemlsza Museum in Madrid. In her new capacity as consultant to the Gallery under the directorship of Jane, Lin will be In attendance at the Gallery by appointment only on Wednesdays for valuations and authentications and also be available for hanging collections both private and corporate. This month Bloorrfleld Galleries Is holding a Norman Lindsay exhibition with a difference. Fifty two small pen and pencil drawings from a folio personally collected by Rose Lindsay and dating from 1900 are a fascinating Insight into Rose's preferences. Pen drawings from Vfefon, studies for published works, Springwood compositions, single figure nudes, motifs for decorations, pen and pencil compositions and numerous others including a kookaburra study comprise this unique exhibition. van" Englund, Walcha based potter, will be shnwjn^frnm Tuesday August 31 tojSeptember 18. Represented In state and regional galleries andjiniverettte^TrTAustralia, Japan, USA, ChinF^ncTRnssia^Jyan Is currently completing his Doctojjle-of^feative Arts at the University of Wollongong. This exhibition, IvanVTkst major solo Sydney showtef-ZtTyears will feature exciting new glazes on a variety of superb pots. All ofjfje-pots exhibit his preferencS'for simple, conventional shapes, are wheel thrown arid^we_b2JjjhJox-deeorattorTln wax, cobalt and peuoxidsa, — Lin's visit to Bulgaria last year proved very successful. Since the collapse of communism a new Ministry for the Arts Is being formed and Lin had meetings with the dynamic Minister of Culture In Sofia (Professor Elka Konstantinova) and, In Varna, the Director of the Varna Art Gallery, foremost Bulgarian artist Vanko Urumov. Privately conducted tours of galleries and visits to artist's studios were arranged. A highlight was the trip to the Tryavna Art School with its ancient tradition of wood sculpture. Bloomfield Galleries will be holding a showing of works by Todor Velln, a Bulgarian artist now living In Sydney from late September to early October. October is Reinhard month! Professor Ken Reinhard, Dean and Director of the College of Fine Arts, University of NSW Is widely represented In state and regional galleries, universities and private collections In Australia and overseas. He has represented Australia in exhibitions In France, USA, New Zealand and Yugoslavia in a variety of media and since his first exhibition at the Macquarie Galleries In 1964 and has been a prominent figure In Ihe Australian art world. Ken's work has always been controversial and this exhibition. The Naked Chair, promises to be a show sfopperl During the first week in November, marine artist Peter Yeomans will be showing his new works, the Venetian Series Peter studied at East Sydney Technical College and St Marlins School of Art, London and In 1988 obtained his post graduate diploma In painting from the College of Fine Arts, University of NSW. Although wel known as a marine artist he has approached diverse subject matter with notable success. In 1993 his Pilot Boarding won the prints and drawing category prize at the P 8,0 Awards, Australian Maritime Museum. In November we will be sending out our last newsletter of the year with information about our final exhibition for 1993. BLOOMFIELD GALLERIES NEWSLETTER - WINTER 1993 118 Sutherland Street, Paddlngton NSW 2021 Australia Ph: (02)326 2122 Fax: (02) 327 8148 Gallery Hours: Tuesday - Saturday 1:00-6:00pm A DMelon of N M Bloomfield Holdlnoe Ply Limited ACM 002 «»» »59 DAVE WOOD GLEN MANNING IVAN ENGLUND CALLIGRAPHY CERAMICS MAJOR EXHIBITION OF NEW WORK 31 August - 18 September 1993 New England Landscape, 1993 ht 43 cm The Bloomfield Galleries EXHIBITION 6-28 AUGUST, 1993 118 Sutherland Street, Paddington NSW 2021 Phone: (02) 326 2122 Fax: (02) 327 8148 OLD BAKERY GALLERY Tuesday - Saturday 1:00 pm-6:00 pm 22 Rosenthal Ave, Lane Cove 2066. PO Box 193. Tel: (02) 428 4565 Gallery Hours: 10 am to 5 pm Tuesday to Saturday ALAN FOX Studio Altenburg AMINITE', 1993. HANDBLOWN GLASS FORM JANE STURROCK NASH FOX STUDIO GLASS 1 OCTOBER-2 NOVEMBER, 1993 cl- POST OFFICE, KARRIDALE, W. AUSTRALIA 6288. 104 Wallace Street, Braidvoood, NSW 2622 TELEPHONE: (097) 586 712 Telephone: (048) 422384 OPFN 10 AM TO 5 PM EVERY DAY IVAN ENGLUND NEW ENGLAND LANDSCAPES An invitation to attend the opening of this major exhibition on Tuesday 31 August 1993 from 6:00pm - 8:00pm Exhibition extends until 18 September 1993 118 Sutherland Street, Paddington NSW 2021 Phone: 326 2122 Fax: 327 8148 NEW ENGLAND LANDSCAPES Catalogue Statement Making pots is not just about pushing clay into some sort of shape and firing it though at its simplest it could be just that. A lifetime could be spent in the study of clays and rocks, the geology of which is the very basis of pottery. Then there is the interest of how clay is shaped. The most direct method of making a pot is to build it by hand from coils or slabs. Many potters still use the potters wheel in one of its many forms to skilfully shape the clay. Slip casting allows not only the repetition of forms but allows unlimited control of shapes. There is scope for designers of pottery forms for factories or for studies and some workers are interested only in decoration or painting. To complete a pot it must be fired so there is a wide field of study in kiln design and building, in fuels and in the various effects of both kiln and fuel best illustrated by the "fire" marks and slaglike glazes beloved of the wood firers with their Bizen type anagama kilns and by the potters who "salt glaze" pots by throwing common salt into the hot kiln. Then there are real glazes. Glaze is closely allied to glass where certain substances are mixed and fired to a temperature where they melt to become glass. The glass worker forms the shape while the glass is in the molten state while the potter applies the glaze mixture to the pot surface to become molten when fired. I have been fascinated by glazes throughout my long career as a potter. I have formulated low fire glazes for a commercial roofing tile company and for many years I worked exclusively in stoneware fired at 1250oC to 1300oC. Glazes can be rough and stony, transparent and glasslike with or without grazing (or crackle!), opaque either in white or offwhite, they can be heavily laced with iron oxide to produce the black tenmokus, tan/orange kaki or greenish crystalline "tea-dust" of oriental pottery. With a minute amount of the same iron oxide it is possible to achieve the incomparable green oeladon "like the blue of the sky after rain". Glazes can be stained with the various metal oxides, cobalt for blue, manganese for brown purple, chrome for dense green and copper for the incredible "copper red", the flambes, the peach blooms and the sang de boeufs. Modern chemists have produced a vast array of stains with which to colour glazes. Many years ago at the Wollongong Technical College I began an investigation into an area of temperatures that had been largely neglected over the centuries; that is the glazes that would be fired at cone 4 or 1160oC. I called such glazes "middle fire" to differentiate them from earthenware and stoneware. In 1990 I started work and research for the degree of Doctor of Creative Arts at the University of Wollongong and chose to further my research into the middle fire glazes this time calculating them to be applied to the unfired pots, the so-called "once fire" or "raw glaze" technique rather than the more usual method of applying the glaze to an already fired pot. The present exhibition shows glazes developed over the last three years in the temperature range of 1100oC and 1200oC and constitutes part of my presentation together with my written submission for the Doctor of Creative Arts degree. All the pots have been thrown on a potters wheel in deliberately simple shapes to allow the glazes full attention. The decoration is simple using wax, cobalt and copper oxides. I present this work as proof of my thesis that excellent glazes are achievable in the middle fire temperature range. Ivan Englund BLOOMFIELD GALLERIES IVAN ENGLUND 31 August -18 September 1993 NEW ENGLAND LANDSCAPES TITLE DATE GLAZE SIZE (mm) PRICE 1. Pared* 1993 Celadon Glaze 280 $200 2. Towards Evening 1993 Chun Glaze 300 $200 3. BIIM Streamer 1993 Red, White and Blue 304 $200 4. Valley Mist 1993 Chun Blue Glaze 320 $250 5. Variations In Blua 1993 Chun Blue Glaze 330 $250 6. Homage to Beryl's Blue 1993 Ilmenite Glaze 350 $250 7. Potntlllst Platter 1993 Ilmenite Glaze 356 $250 B. Seaside 1993 Cobalt Glaze 360 $250 9. Misty Morning 1993 Chun Glaze 325 $260 10. Fiery Landscape 1993 Copper Red Glaze 360 $260 11. Gesture In Blue 1993 Blue and White 295 $275 12. Celebration in Red 1993 Copper Red Glaze 340 $275 13. Dreams of Summer 1993 Red and Blue Brush 290 $280 14. Polntlllst Blue 1993 Ilmenite Glaze 375 $280 15. Iron Landscape 1993 Iron Oxide 340 $290 16. Hanko 1993 Basalt Glaze 320 $300 17. 1 Hear the Creek Falling 1993 Cobalt Glaze 375 $300 18. Heraldic Pelican 1993 Blue and White 395 $300 19. Dawn 1993 Grey Glaze 405 $300 20. Marine Sunset 1993 Copper Glaze 410 $300 ...2/ Gallery Hours: Tuet - Saturday 1:00pm - 6:00pm Mornings by appointment 118 Sutherland Street, Paddington NSW 2021 Phone: (02) 326 2122 Fax: (02) 327 8148 BLOOMFIELD GALLERIES D7AN ENGLUND Page 2 TITLE DATE GLAZE SIZE (mm) PRICE 21. Windblown 1993 Wax Resist and Blue 320 $375 22. Winter Landscape 1993 Wax Resist and Blue 320 $375 23. Afterglow 2 1993 Copper Variations 340 $375 24. Trees and Hills 1993 Blue and White 360 $375 25. Evening Sky 1993 Red Copper 310 $380 26. Southeaster 1993 Wax Resist and Blue 315 $380 27. May 5th 1993 Cobalt and Copper 320 $380 28. Wedding Dat 1993 Copper Speckle 370 $380 29. Afterglow 1 1993 Copper Variations 410 $380 30. Blue Group 1993 Blue and White 445 $380 31. Gala 1993 Matt Glaze 460 $390 32. Towards Ebor 1993 Celadon Glaze 385 $400 33. Tablelands Landscape 1993 With Blue Oxides 415 $400 34. Looking South 1993 Cobalt Painted 440 $400 35. Blue Border 1993 Cobalt and Copper 470 $400 36. New England Landscape 1993 Blue on White 495 $400 37. The Blue Poplars 1993 White with Cobalt 480 $420 38. Fire Shower 1993 Basalt Glaze 480 $450 39. Valley Dawn 1993 Copper Glaze 485 $450 40. Cool Valley 1993 Varied Copper Glaze 490 $450 Gallery Hours: Tues - Saturday 1:00pm - 6:00pm Mornings by appointment 110 Sutherland Street, Paddington NSW 2021 Phone: (02) 326 2122 Fax: (02) 327 8148