The Glass Bathyscaphe
ALAN MACFARLANE is Professor of Anthropological Science at the
University of Cambridge and a Fellow of King’s College and of the
British Academy. He is a well-known author and television presenter.
His fourteen books include Witchcraft in Tudor and Stuart England, The
Origins of English Individualism and The Riddle of the Modern World.
GERRY MARTIN is a former Managing Director and co-founder of
Eurotherm Ltd. He has also long been a historian of glass instruments,
particularly microscopes.
This paperback edition published in 2003
First published in 2002 by
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Copyright © Alan Macfarlane and Gerry Martin 2002
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ISBN 1 86197 394 2
For Sarah and Hilda
Preface
List of Illustrations
1 Invisible Glass
2 Glass in the West – from Mesopotamia to Venice
3 Glass and the Origin of Early Science
4 Glass and the Renaissance
5 Glass and Later Science
6 Glass in the East
7 The Clash of Civilisations
8 Spectacles and Predicaments
9 Visions of the World
Appendixes
1 Types of Glass
2 The Role of Glass in Twenty Experiments that Changed the World
Further Reading
Sources for Quoted Passages
Bibliography
Index
THIS IS A BOOK about change, especially about how the presence of glass and the way in which humans have used glass has enormously accelerated change (and conversely, the absence of glass has slowed it down). There is a very strong human tendency when studying the past to try to identify individuals who have made history, to make them heroes, or at least key figures in explaining how events have unfolded. This is particularly tempting in trying to understand discovery and innovation. This tendency always lead to distorted history for change arises out of the combined activities of dozens, hundreds, or even thousands of individuals. Yet we often label a particular innovation or invention with the name of an individual as a shorthand or convenience. It is within that framework that the mention of particular named individuals in this book should be interpreted.
This also applies to the writing of the book. Though two named authors have written it it is impossible to disentangle their contributions. Likewise they are just part of a much larger network of friends, authorities and contacts who have contributed to this single book. Among those whose influence is most direct and obvious to us are the following. Professors Chris Bayly, Mark Elvin and Caroline Humphrey, and Drs Su Dalgleish, Simon Schaffer and David Sneath made various suggestions which were particularly helpful. Kim Prendergast carried out the survey of school classes and schoolteachers in South Korea and arranged our visit to a school there. Professor Tokoro, David Dugan and Carlo Massarrella helped specifically in relation to myopia in Japan and the latter two more generally in developing our ideas on glass. Our thanks also to Stephen Pollock-Hill of Nazeing Glass.
The whole book was carefully read and commented on by John Davey, Sally Dugan, Iris Macfarlane and Andrew Morgan. John Davey also acted as the editor. Mark Turin kindly checked the text in proof stage.
Sarah Harrison thought of the idea of narrowing down our focus to glass. She inspired us to put the academic paraphernalia and quotations elsewhere (www.alanmacfarlane.com/glass). She read through the text and made many valuable suggestions. To her, and to Hilda Martin who has also helped in many ways, we dedicate this book in gratitude for their support in our endless quest.
1 Early Egyptian glass, c. 1370 BC
Reino Liefkes (ed.), Glass (V & A Publications, 1997), p. 13
2 An eighteenth-century English lead glass
Reino Liefkes (ed.), Glass (V & A Publications, 1997), p. 90
3 Glass, alchemy and chemistry
Johannes Stradanus, ‘The Alchemist’, Palazzo Vecchio, Florence, reproduced from William H. Brock, The Fontana History of Chemistry (1992), cover
4 Apparatus used by Priestley
Priestley, Experiments and Observations on Different Kinds of Air, vol. I (1774), reprinted in Aaron J. Ihde, The Development of Modern Chemistry (Dover Publications, 1984), p. 42
5 Going up the river
Chang Tese-tuan (active c. 1100–1130), ‘Going Up River at Ch’ingming Festival Time’. Detail of a handscroll. Ink and slight colour on silk. Palace Museum, Peking. Reprinted in Michael Sullivan, The Meeting of Eastern and Western Art (University of California Press, 1989), p. 260
6 Dürer’s drawing device
Dürer’s Underweysung, 1st edn., Nuremberg, 1525, reprinted in Martin Kemp, The Science of Art (Yale University Press, 1990), p. 172 65
7 A compound microscope by Robert Hooke
From Hooke, Micrographia, 1665
8 Pasteur’s bottle
Used in his researches on spontaneous generation in 1860
9 Harrison’s chronometer
Original in National Maritime Museum, Greenwich, Inv.no.Ch.38, reprinted in William J.H. Andrews (ed.) The Quest for Longitude (Harvard University Press, 1996), p. 240 96
10 Pines and rocky peaks
Left: ‘Rain’ by Sansetsu, British Museum. Right: ‘Pines and Rocky Peaks’ by Ma Yüan. Collection of Baron Yanosuké, Tokyo. Reprinted in Laurence Binyon, Painting in the Far East (Dover Publications, 1969), pp. 206, 154.
11 Two views of Derwentwater
Top: Chiang Yee, ‘Cows in Derwentater’, 1936. Brush and ink. Bottom: Anonymous, ‘Derwentwater, looking toward Borrowdale’, 1826. Lithograph. Reproduced in E.H. Gombrich, Art and Illusion (Phaidon, 1960), p. 74
12 Concave lens for myopia.
Jan van Eyck, ‘Madonna and Child with Canon von der Paele’ (detail), 1436. Oil on panel, Groeningemuseum, Bruges.
13 Myopic children in China
Photograph reproduced in Otto Rasmussen, Chinese Eyesight and Spectacles (1950), p. 58.
‘… guessing before demonstrating! Do I need to remind you that this was how all important discoveries are made?’
Henri Poincaré
MOST OF US hardly give glass a thought, but imagine waking in a world where glass has been stripped away or uninvented. All glass utensils have vanished, including those now made of similar substances such as plastics which would not have existed without glass. All objects, technologies and ideas that owe their existence to glass have gone.
We feel for the alarm clock or watch: no clock or watch, however, for miniaturised clocks and watches cannot exist without the protective facing of glass. We grope for the light switch. But there can be no light switch, for there is no glass for the light bulb. When we draw back the curtains a blast of air strikes us through the glassless windows. If we suffer from short sight, we can see clearly for about ten inches. If we have long sight, as we probably do if we are over fifty, we will not be able to read. There are no contact lenses or spectacles to help us.
There is no clear mirror in the bathroom to shave by, no bottles of ointments or glass for our toothbrush. There is no television in the living room, for with no screen it cannot exist. When we look out of the windows we see no cars, buses, trains or aeroplanes, for without windscreens none of them can operate (and they almost certainly have not been developed anyway). The shops in town have no window displays and our gardens no glasshouses. In the evening the streets flicker with torch-light. The central heating owes more to the Romans than the Victorians. We shiver in the darkness.
These are a few examples of what would be likely to happen if glass left our lives. Even more striking would be the way in which almost everything else would be affected. There would almost certainly be no electricity, since its first generation depended on gas or steam turbines, which required glass for their development. So there would be no radios, no computers, or email. There might well be no running water. Clearly we could not cook with electricity and there would be no freezers or fridges. There might also be surprisingly little use of non-human energy in what remained of industrial production. Our fields would produce less than one twentieth of their current yield without the fertilisers discovered by chemists using glass tools.
In our hospitals medicine would be killing more people than it cured. There would be no understanding of the world of bacteria and viruses, no antibiotics and no revolution in molecular biology from the discovery of DNA. As there would be little control of epidemic and endemic diseases these would everywhere be as rife as they were at the end of the eighteenth century.
Our understanding and control of space would be very limited. We might not even be able to prove that the earth goes round the sun. Our astronomy would be ancient and our weather prediction haphazard. Long-distance navigation would lack accurate tools for measuring longitude and latitude, and, of course, there would be no radar or radio communications, let alone the telephone and telegraph, to help us when we were lost.
The artistic and aesthetic world would also be entirely different. Not only would there be no photographs, films and television: our very concepts of space, perspective and reality would be radically different. There would have been no Renaissance discovery of how to represent three-dimensional space and our systems of representation might not be far removed from those of the twelfth century.
This book shows just how central glass is to every aspect of our lives. It is true that other substances, such as wood, bamboo, stone and clay, can provide shelter and storage. What is special about glass is that it combines these and many other practical uses with the ability to extend the most potent of our senses, sight, and the most formidable of human organs, the brain.
Through mirrors and lenses glass makes us feel differently about ourselves and about the world. Telescopes, microscopes and spectacles let us see the distant and the near in ways which the human eye unaided cannot do. Through barometers, thermometers, vacuum flasks, retorts and a whole panoply of other instruments, glass enables us to isolate chemicals and test theories about their properties and interactions. Glass allows a representation of nature to be captured accurately and stored and then transmitted over long distances without distortion. Glass, in short, influences every sphere of our lives.
Since the middle of the twentieth century, alternatives to glass have been developed and it now seems less irreplaceable. The windows of Chartres or King’s College Chapel may never be exchanged for coloured perspex nor fine wine drunk from plastic, but glass is widely being superseded by other transparent materials. The time may come when our world would not collapse if glass disappeared as it undoubtedly would now, but this has no bearing on the degree to which glass technology was an important factor in improving wellbeing and knowledge in the millennia when modern civilisations evolved.
We live in a glass-soaked civilisation, but as for the bird in the Chinese proverb who finds it so difficult to discover air, the substance is almost invisible to us. To use a metaphor drawn from glass, it may be revealing for us to re-focus, to stop looking through glass, and let our eyes dwell on it for a moment to contemplate its wonder.
When we do notice glass we may find it difficult to place, for it tends to slip between categories. This is one source of its attraction and power. Glass is strange. Chemists find it defies their classifications. It is neither a true solid nor a true liquid and is often described as a ‘fourth state of matter’. For a long time it baffled scientists, who could not find any crystalline structure within it. Glass is brittle, which is one of its weaknesses, but it is also enormously durable and flexible and, in the creative hands of an experienced and knowledgeable craftsman, it is almost infinitely malleable.
Glass, wrote Raymond McGrath and A. C. Frost in 1961,
can take any colour and, though possessing no texture in the ordinary sense of the word, any surface treatment. As for responsiveness to light and shade, it has no serious competitor. It is capable of extreme finish and delicacy, is clean, durable and compact, and may be graduated almost imperceptibly from transparency through translucency to opacity, from perfect reflection through diffusion to the completely matt surface. There is, in fact, hardly any surface quality that it cannot assume. Yet at the same time it has a highly characteristic nature and in whatever manner we treat it or whatever surface we impose upon it, it still retains that unmistakable ‘glassiness’. Whether it is embossed, engraved, painted, sand-blasted, mirrored, impressed with any pattern we choose, moulded, blown, flashed and so on – there is almost no limit to what it will endure or to the possible permutations and combinations of the different treatments – its vitreous qualities remain its decorative raison d’être.
In the early days of glass people were concerned less with its utility, which only later became apparent, than with its beauty. Glass was developed first to satisfy our aesthetic delight, later for its use in magic and then, through one of those great accidents of history, its light-bending capacities turned it into the most important avenue to truth about the natural world – a good illustration of John Keats’s famous assertion that ‘beauty is truth, truth beauty’. The awe-inspiring nature of glass was captured nearly sixty years ago by one of its great historians, W. B. Honey:
Glass is nowadays too familiar to arouse all the wonder it deserves. Intrinsically wonderful as the product of mere sand and ashes it may be the occasion of further miracles when made into vessels. For its beauty never seems to be wholly the result of calculation. Its forms may be designed and controlled, its colour may be named and secured by a percentage of oxides; but beyond all these there is a quality in the material that defies prediction, and the play of light and colour within it, its insubstantial air, and the ‘pattern of a gesture’ which its form so often quite literally records, are only the chief elements, perhaps, in the beauty it may assume at the will of the artist.
The history of glass as a technology of thought has attracted surprisingly little sustained attention from scholars. Its development is commonly assumed to have been roughly similar over most of the world. If we think about glass at all, most of us assume that, having been invented some thousands of years ago, its making spread over Europe and Asia. It was then used everywhere in more or less the same ways and to the same extent, and that it has so continued up to the present. We may be dimly aware that it reached a peak in Venice during the Renaissance, but otherwise it mainly seems a very useful and available substance.
One purpose of this book is to give second thoughts to such assumptions and received wisdom. We want to share our surprise at discovering, for example, that glass was practically non-existent in most civilisations and that, where it was present, its role has varied enormously. We were equally surprised to find that it does not follow that once glass has been invented it will be used and also that some civilisations used glass and then gave it up. We hope also to recapture the sense of the astonishing nature of glass so vividly expressed by Dr Johnson in 1750:
Who when he first saw the sand and ashes by a casual intenseness of heat melted into a metalline form, rugged with excrescences and clouded with impurities, would have imagined that in this shapeless lump lay concealed so many conveniences of life as would, in time, constitute a great part of the happiness of the world. Yet by some such fortuitous liquefaction was mankind taught to procure a body at once in a high degree solid and transparent; which might admit the light of the sun, and exclude the violence of the wind; which might extend the sight of the philosopher to new ranges of existence, and charm him at one time with the unbounded extent of material creation, and at another with the endless subordination of animal life; and, what is of yet more importance, might supply the decays of nature, and succour old age with subsidiary sight. Thus was the first artificer in glass employed, though without his knowledge or expectation. He was facilitating and prolonging the enjoyment of light, enlarging the avenues of science, and conferring the highest and most lasting pleasures; he was enabling the student to contemplate nature, and the beauty to behold herself.
To follow Dr Johnson’s vision we travel widely in time and space, going back ten thousand years and moving over the whole known globe. The journey has not always been easy. To understand the enigmatic history of glass requires the insights and methods of many arts and sciences each of which has perceived a part of the story but, like the blind philosophers who each touched only one part of the elephant, cannot imagine the whole.
The lack of a rounded overview is well illustrated by the treatment of glass in the museums we examined when researching this book. The Victoria and Albert Museum in London and the Fitzwilliam Museum in Cambridge display fine drinking glasses and mirrors. The National Science Museum shows lenses and prisms and the British Museum archaeological and art objects. By assembling these collections in a virtual memory museum, we began to put together the shattered history of this extraordinary substance. But none dealt with windows. It was King’s College Chapel, a few yards from where we wrote, with its medieval stained glass, that reminded us of one of the central roles of glass in history.
We found the fragments of an account scattered in the work of historians of art, technology and science, and of anthropologists, biologists, chemists and opthalmologists. Anyone who hopes to bring glass into focus thus has to travel lightly through many disciplines despite the warnings of good sense to remain within one’s competence. We have thus been heavily dependent on experts in other fields, some of whose work is listed in the section of further reading at the end of the book. Because glass is such a complex substance and its influence so little studied, it can be difficult to prove its effects. We may sense, for example, that the mirror shaped our notions of the individual, or that lenses changed optics and profoundly affected the Renaissance. Yet it is hard to prove these connections beyond all argument. We suggest links and hope they are plausible and satisfying. People are wary of too much guesswork; this book contains a fair amount of it. However, we have not disguised our guesses when we have had to make them. It can also be fairly said that discovery sometimes occurs after a first rough set of guesses has begun to seem plausible enough to justify detailed examination. We hope our reasoning here will stimulate others to investigate the degree to which our arguments and conclusions are right or wrong.
During the last thousand years something quite extraordinary has happened in the world. The population of human beings has risen immensely, yet there is far more food to feed them as a result of changes in agriculture. The resources of available energy have vastly expanded. Life expectancy has generally increased as understanding of disease has improved. These and many other changes are part of the increase in reliable knowledge. That increase, we think, would not have been possible without glass. In telling something of its fascinating story we hope also to have shed some light on how our world came to be as it is and how we have come to be as we are.
Hail, holy Light, offspring of Heav’n’s first-born,
Or of th’ Eternal co-eternal beam
May I express thee unblamed? Since God is light,
And never but in unapproachèd light
Dwelt from eternity, dwelt then in thee,
Bright effluence of bright essence increate.
John Milton, Paradise Lost, Book III, lines 1–6
NO ONE IS CERTAIN WHERE, when or how glass originated, but for the purposes of this book this does not matter greatly. The where can broadly be answered by suggesting origins in the Middle East, perhaps in more than one place, including Egypt and Mesopotamia. As to when, some estimate the origins of glass at between 3000 and 2000 BC, while others suggest hints of glazing on pottery as early as 8000 BC. As to how, all is complete guesswork and we can only say that it was originally made by accident.
The earliest forms of glass were not transparent. We can see this when the number of recovered glass objects suddenly increases, in about 1500 BC. This was also the time when the ‘core-formed’ technique was developed. One of the two major techniques was as follows. A stick was covered in clay, then dipped into a crucible of heated glass and withdrawn so that it was covered in glass. The glass was smoothed with a slate and made to cover one end of the clay lump. After cooling, the stick was pulled out and the clay scraped away. Thus a hollow tube of glass, with whatever decorations had been scraped on the surface, could be made. At that point glass making extended along much of the eastern end of the Mediterranean and, through Phoenician merchants, was set to spread through the Greek islands and North Africa. It was seen as a substance which could mimic others, it was like clay, or could be used to imitate precious stones. It was not transparent. In this period glass was used for three purposes: to glaze pottery, for jewellery and to make small containers, mainly for liquids.
1. Early Egyptian glass
An early Egyptian glass, made in about 1370 BC for storing liquid. Most early glass was opaque like this and it was well over a thousand years before clear glass became popular. Glass was thus long regarded as an alternative to pottery, or as a way of making replicas of opaque precious stones.
Somewhere between 1500 BC and the birth of Christ, perhaps around 500 BC, glass-making techniques spread to east Asia and were known to the Chinese. Thus by about 100 BC much of Eurasia had a common knowledge base of how to make coloured and plain glass. Its use continued to be mainly for the same purposes, glazing pottery, jewellery and containers.
Glass-blowing, which opened up endless new possibilities, was developed at some point in the century before the birth of Christ. Somewhere in Syria or Iraq, a revolutionary new technique of making glass artefacts was introduced. Up to this point glass objects were made by casting and grinding. Then came the invention of glass-blowing. This involved the use of a long iron tube of at least a metre in length which was dipped into the molten glass to pick up a lump. The blower then blew the glass into a bubble. We tend to think of this as an obvious development but it needed a highly sophisticated awareness of the properties of glass and its potential to reach this point. Technically it required heating glass to a much higher temperature than for moulding or casting. It needed to be very liquid. This required a knowledge and experience of furnaces that had developed in the glass industries of the Middle East. With the introduction of glass-blowing, really thin, transparent glass could be made. This new technique enormously increased the versatility of glass and, in particular, opened up potentially new uses.
It is really just over two thousand years ago that the great divergence in its use in east and west Eurasia began. In order to trace the causes and consequences we have to examine the various civilisations separately. We shall do so in relation to five major uses of glass. The first three are usefully distinguished using the more specific French terms for forms of glass instead of the collective English noun ‘glass’: ‘verroterie’ for glass beads, counters, toys and jewellery, ‘verrerie’ for glass vessels, vases, bottles and other utilitarian wares; and ‘vitrail’ or ‘vitrage’ for window glass. To this we may add two more. There are mirrors, and there are lenses and prisms, including such applications as spectacles.
The Romans have a central place in the history of glass. They provided not only the technical skills, but also a sense of glass as an important material in its own right. Roman glass technology was in many ways unrivalled until the nineteenth century. Yet it was the revolution in attitudes which was the most important feature in the development of the peculiar place of glass in the west. It is this attitude towards glass which distinguishes the history of glass in western Europe from its history in Asia.
The possibilities for innovation coincided with the peak of Roman civilisation, which placed glass at the centre of its interior decorative development. With the development of glass blowing it was possible to produce glass vessels cheaply and in large quantities. Glass was such a versatile, clean and beautiful substance that fine pieces became highly prized and symbols of wealth. Its success was so great that it began to undermine its main competitor, ceramics. Glass was principally used for containers of various kinds: dishes, bottles, jugs, cups, plates, spoons, even lamps and inkwells. It was also used for pavements, for coating walls, for forcing frames for seedlings, and even for drainpipes. It is no exaggeration to say that glass was used for a wider range of objects than at any other time in history, including the present. It was especially appreciated for the way it enhanced the attractiveness of the favourite Roman drink, wine.
In order to appreciate the colours of wine it was necessary to see through the glass. Thus another development, with great implications for the future, was the realisation that clear glass was both useful and beautiful. In all civilisations up to Rome, and in all other civilisations outside western Eurasia, glass was chiefly valued in its coloured and opaque forms, particularly as an imitation of precious stones. The long-term consequence of the perfecting of clear glass manufacture was the development of glass as a thinking tool, through mirrors, lenses and spectacles.
In their cutting, engraving, painting, gilt decoration and designs the Romans were greatly advanced. They knew all the tricks of the glass blower’s trade and many of their fine pieces were as good as anything produced for many centuries after.
The technical ability of Roman glass craft workers meant that in terms of both the diversity of the objects which they made, and the quantity, it could be claimed that Roman civilisation was more glass-soaked than any other until the very recent past. This was partly due to the cheapness of the product. Every part of the huge empire could be supplied with glass. Rubbish heaps and middens suggest that glass utensils were thrown away when only slightly damaged as it was cheaper and easier to buy a new one than repair the old.
Of the five major uses of glass which we have suggested, the Romans developed two in particular, verroterie (glass beads, etc.) and verrerie (glass vessels and other domestic ware). But the other three uses, which would be the great developments of medieval Europe, although perfectly practicable and indeed known about, were not adopted to any great extent. These were vitrail (window glass), mirrors and lenses.
It is quite evident that the Romans could make good windows of glass, and occasionally did so. Window glass was apparently made by casting, and pieces of considerable size could be made. There is evidence for this from the Roman town of Pompeii. Other examples have been found in Roman houses in Italy and elsewhere. Yet most experts are surprised at the slow development of window glass in Italy. This is usually explained by the warm Mediterranean climate and the use of mica, alabaster and shells as cheaper alternatives. It may be that the large, flat panes of glass were rather crude and the imperfections meant that those who could afford them did not really see them as necessary for enhancing the beauty of their houses. For whatever reason, windows were not a major development in the south. As one moves towards northern Europe there is more evidence of glass windows, suggesting that the climate argument is correct. In Britain they were quite common after the Roman invasion and even reached beyond the frontier of the Roman Empire into southern Scotland. It was in northern Europe that window technology developed and flourished after the fall of Rome.
The Romans knew how to make glass mirrors, yet metal mirrors were preferred. Archaeological investigations have uncovered only a few examples of the former. The glass was generally coated with tin or, more rarely, silver. It was used in hand-mirrors but larger mirrors in which a man could see himself from head to toe have also been found.
Likewise, the use of glass to magnify objects was probably known. A little glass ball filled with water may have been used for fine work, such as engraving gems, but the Romans did not develop lenses, prisms and spectacles. Glass as a tool for obtaining reliable knowledge, either in optics or in chemistry, does not seem to have been developed to any significant degree. The Romans had laid the foundations for a world of glass, but the philosophical effects of this strange substance were not yet felt.
Our difficulty in understanding the influence of glass is partly caused by a widespread, but mistaken, impression. Most of us would assume that however wonderful the Roman glass was, all this was more or less lost to the west after the collapse of the Roman Empire. This makes superficial sense; the craftsmen would have been killed or dispersed and the market for glass would vanish. Furthermore, for a long period this assumption seemed to be borne out by the archaeological record. Far less glass dating after about AD 400 was dug up and what there was seemed to be of inferior quality. The apparent dearth of glass seemed a characteristic of Europe until as late as 1400; the destruction of Rome appeared to have left a glass vacuum for nearly a thousand years. Even experts on glass believed this until about two decades ago.
With such a picture it is very difficult to see that glass could be a technology which made a great difference. If western Europe more or less lost glass for a thousand years, it could hardly be in advance of other civilisations in this respect. And if there was little glass in western Europe by 1100, we would tend to think that it would take some centuries for it to revive, making its influence felt only from about the sixteenth century. This picture needs to be revised drastically. This will provide a very different link in the argument, for it can be shown that while there was certainly a decline in manufacture, much of the Roman legacy was maintained and, in some ways, improved upon even by 1200.
Archaeology can be misleading. Undoubtedly there was a very rapid loss in the quality and quantity of glass objects found after about the fifth century, and there seems to be little increase in the quantity even after the economic recovery of Europe from the eighth century. But this may not be a reflection of what happened, but rather of three other factors. Firstly, the development of Christianity meant that very few objects, including glass ones, were now placed in graves, the major source of Roman glass artefacts. Secondly, we know that broken glass was collected for recycling. Thirdly, much of the glass in Europe after the ninth or tenth century was made using potash made from the ashes of woodland plants such as bracken and beechwood, rather than from marine plants. The result is that glass objects made in this way are much more likely to decay than Roman glass, especially when buried in acid soils.
A final fact is that the assumption that glass had disappeared meant that those who did do some digging did not always notice what glass there was. This was compounded by the fact that until quite recently there was little serious archaeological work on early medieval Europe. The situation has now changed and the relatively young discipline of medieval archaeology has revealed a wealth of medieval glass. Excavations have transformed our knowledge and shown, as we might have guessed when we looked at the glorious stained glass in medieval churches, that it was widespread, made by craftsmen with great technical skill and confidence.
What then is the new picture that is emerging for the period between AD 500 and about 1200? It firstly incorporates a little of the old story, a half-truth which should not be entirely lost. It is indeed true that, particularly north of the Alps, the collapse of the Roman Empire led to a considerable loss of technical skill and quantity of output for a while. Yet rather than a complete break, we can now see a picture of a decline combined with continuity. There was a diminution of quality and quantity, but glass techniques were maintained and the high regard for the substance was not lost.
One of the reasons for our mistaken assumptions lies in the fact that much of the continued production occurred on the edges of the old Roman Empire. The centres of glassmaking moved up into Germany, northern France and England. The Roman love of glass had spread as far as Afghanistan and the central Sahara, and as far north as Scotland and Scandinavia. When the barbarians overran the Roman Empire, they had already absorbed glass as an essential part of their lives, and this tradition continued. Thus recent research suggests that the Roman collapse had far less effect on the glass-makers north of the Alps than was once thought.
The Romans had learnt from the originators of glass in the eastern Mediterranean, but had then returned the gift by enriching glass-making there. Even before Rome collapsed, northern European glass-making was benefiting from the eastern influence and it continued to reinvigorate glass making after the collapse of the Roman Empire. A reservoir of skills and knowledge was maintained in Syria, Egypt and the Eastern Empire after the fall of the Roman Empire and it is quite clear that this had a dramatic effect on northern glass-makers. Immigrant glass-makers from the eastern Mediterranean spread across Europe and improved the techniques, particularly in north-western France.
Thus, after the fall of Rome the situation was far from static. Much of the old Roman technique was preserved, but through the centuries in the north the making of glass changed. For example, Roman techniques were replaced by new styles of glassware, mainly drinking vessels, known variously as Frankish, Merovingian or Teutonic. It is worth noting three especially important influences which bent the early Roman excellence in new directions as well as helping to preserve the great tradition.
One of these was Christianity and the introduction of glazed windows, particularly in churches, then the further development of painted and stained glass manufacture. There are references to such windows from fifth century France at Tours, and a little later from north-east England, in Sunderland, followed by developments at Monkwearmouth, and in the far north at Jarrow dating to the period between 682 and c. 870. By AD 1000 painted glass is mentioned quite frequently in church records, for example in those of the first Benedictine Monastery at Monte Cassino in 1066. It was the Benedictine order in particular that gave the impetus for window glass. It was they who saw the use of glass as a way of glorifying God through their involvement in its actual production in their monasteries, injecting huge amounts of skill and money into its development. The Benedictines were, in many ways, the transmitters of the great Roman legacy. The particular emphasis on window glass would lead into one of the most powerful forces behind the extraordinary explosion of glass manufacture from the twelfth century.
Apart from the addition of window glass, until 1100 the two main uses for glass had been for verroterie (beads, toys, jewellery) and verrerie (vessels). The period between 1100 and 1700 saw the continued development of the two earlier uses, especially in relation to fine drinking glasses. Windows, both of stained glass in religious buildings and of plain window glass for ordinary homes, became increasingly common. Similarly, there were improvements in both quality and size of glass mirrors as luxury items for the home. The new use for glass was in the development of lenses, prisms and spectacles, that is glass for optical purposes. Windows, mirrors and optical glass would change the knowledge base of Europe. None of these were manufactured to any extent elsewhere in this period.
It seems likely that the tradition of glass-making never died out in Italy after the fall of Rome, especially in the northern Adriatic area around Venice. Yet it was really from the thirteenth century that Italian, and particularly Venetian, glass-making began to influence the whole of Europe. By the early fourteenth century glass production was widespread and in the following century the techniques improved further, probably heavily influenced by events in the eastern Mediterranean. In particular the destruction of the city of Damascus (a great glass centre) by the Mongolian war-lord Timur the Great in 1400 probably led to an influx of craftsmen to Italy, as may also have happened in 1453 when Constantinople finally fell to the Turks.
Two particular technical developments in glass making laid the foundation for glass of a high enough quality to underpin the Knowledge Revolution. The first of them also shows how the recovery of the skills of ancient Roman glassmakers was an important influence. The glass-makers on the island of Murano, near Venice, experimented with Roman glass techniques and towards the end of the fifteenth century they developed a method of making glass in which thin canes of multicoloured glass are embedded, known as millefiori. Even more important was the development of crystal or (cristallo glass), a word first mentioned in 1409. It can be thin, almost weightless, free from flaws and colourless and it enabled the glass-makers to make wonderfully elegant and intricate forms. Its purity and thinness was an object of fascination and desire. Thus it fed into the artistic renaissance that was occurring in northern Italy at this time.
There is circularity in the development of glass in any civilisation that depends mainly on how it is perceived, but likewise, how it is perceived is dependent on its quality and versatility. As glass-making improved, so did the desire for it and hence money flowed into further improvements. Thus the glass-making explosion in Italy is not merely an automatic result of the increasing wealth of Europe from the twelfth century onwards. It is linked to many other forces, intellectual and cultural.
One of these was the growing fascination with curious and precious substances, particularly among Renaissance patrons. Rock crystal was especially prized, since it was thought to have magical properties. But it was available only to the rich. Fine glass became a cheaper substitute, just as beautiful and more versatile. The Venetian glass-makers also began to imitate many of the other beautiful hardstones such as agate, jade, jasper and lapis lazuli and to use them in all sorts of forms from cups to candlesticks as well as for beads.