2009 marks the 50th anniversary of the announcement of the float glass process, yet very little has been published about the history of the invention since the initial flurry of articles in the 1960s. This literature was carefully edited both for accuracy and obscurity in order to protect the commercial value of the invention. Later publication was discouraged and persistent litigation inhibited access to the archive. Inevitably a mythology has grown up about the invention and Sir Alastair Pilkington's flash of insight at the kitchen sink. This paper sets out new research based on unique access to the Pilkington archive which explores precisely what Sir Alastair invented and when, and places the invention in the context of other work being done at the time.

Dr David Bricknell

After a long and distinguished career in the glass industry, David Bricknell chose to begin his retirement with historical research to uncover the real roots of the most significant glassmaking invention of the twentieth century. The impact of the Float Glass process on global society is incalculable. As well as earning him the degree of Doctor of Philosophy, David’s research has borne fruit in the recent publication of the definitive book on this topic.

In 1769 the Portuguese King D. José I and his prime-minister Marquis of Pombal greatly supported William Stephens, allowing him to re-establish a previous ruined glass production centre that bankrupted under John Beare administration in 1767. The production at the new Royal Glass Manufacture in Marinha Grande started ca. 1770 and was administrated by Stephens until 1792. In this work some arcanes written by William Stephens are examined, providing a new insight into the methods and knowledge then available. More than a simple collection of recipes,  the arcanes are experimental notebooks where the results obtained with different formulations are carefully compared and discussed. Stephens criticized his experiments within a surprisingly modern scientific perspective, although the influence of pre-scientific alchemic tradition is still noticeable. His results allowed him to refine his expertise in the art of glass colouring and to obtain truly original recipes. An attempt to clarify the chemical nomenclature and glass jargon used by Stephens was made and the probable sources of the raw materials were investigated. The production methods and equipment used in the last quarter of the 18th century at Marinha Grande are discussed. A few glass samples were reproduced using several compositions referred in the arcanes to check the validity of the proposed nomenclature and to investigate the conditions used to obtain the colours. The involved chemical redox equilibria and its influence in the optical properties is discussed. Micro-X-ray fluorescence (micro-EDXRF) and UV-Vis absorption spectrometry were used to characterize and compare laboratory reproduced samples with museum collection items seemingly attributable to the Stephens production period at Marinha Grande.

Professor António Pires de Matos

António Pires de Matos was a senior researcher at the Nuclear and Technological Institute where he worked since 1963. He was invited full professor at the Universidade Nova de Lisboa during seven years where he taught instrumental analysis in the Department of Conservation and Restoration. Recently his interests were focused on glass research. He is coordinating the research unit “Glass and Ceramics for the Arts” (www.vicarte.org) at the Universidade Nova de Lisboa which is running an interdisciplinary program on glass science in contemporary art, conservation and archaeometry. He will be responsible for the coordination of the “Master of Glass Art and Science” course which starts in September 2009.

The ancients were able to distinguish between beautiful (single) crystals such as rock crystal (quartz), with their characteristic faceted shapes, and natural glass such as obsidian with its conchoidal fracture properties that made it invaluable for cutting blades and arrowheads. To scientists the question asto what constitutes a glass is still the subject of considerable controversy, especially given the wide variety of new glass-forming systems discovered during the past 100 years. The present paper considers the various attempts that have been made to express what we mean by “glass”. An early attempt by Christopher Merret in his 1662 translation of Antonio Neri’s L’Arte Vetraria defined glass in terms of 26 characteristic properties. However, some of these properties are also found for crystalline materials, whilst others are not exhibited by many more recently discovered glasses.

Another, much more recent, approach considers the disordered atomic structure of glass, but again this in itself is not unique to the vitreous state. Other kinds of solids with a non-crystalline disordered molecular structure can be prepared in many different ways, for example by condensing water vapour on a very cold substrate to form amorphous ice.

Perhaps the best “glass” definition to date considers the formation process. The most popular wording by the American Society for Testing and Materials, "Glass is an inorganic product of fusion which has cooled to a rigid condition without crystallizing. "incorporates a gross error! Glasses having more than one component are NOT (initially) a product of fusion; they are a product of chemistry, as already realised by Samuel Parkes in 1812: “The sister art, that of making GLASS, is also entirely chemical.”The process by which soda-lime-silica glass is formed from its raw materials involves a chemical reaction between the basic sodium and calcium carbonates and the acidic silicon dioxide. At the temperature of the reaction, the products are liquid and, once the reaction is complete, the glass can be quenched from the resulting liquid. Thus our understanding of glass is helped if we  think of it as "an inorganic material that has been quenched from the liquid to a rigid state without crystallising."

Professor Adrian Wright

Based for many years at the prestigious J.J. Thomson Physical Laboratory, University of Reading, Emeritus Professor Adrian Wright has an international reputation for his expertise in the field of the molecular structure of glasses and amorphous solids. A past President of the Society of Glass Technology, he is a prolific author of research papers and has organised many international conferences on glass.

The widespread adoption of coalfired furnaces by English glassmakers during the 17th century signalled the beginning of a revolution in glass manufacturing, particularly in terms of furnace design. Major advances were realised after the middle of the 19th century as this revolution gathered pace, and the limitations on output imposed by furnace and crucible size were addressed. Key technological breakthroughs in these fields included the introduction of regenerative furnaces, the replacement of the coal fire with a remote gas supply, and the development of the continuous tank furnace. Recent archaeological excavations of the Percival, Vickers glassworks in Manchester, and the Powell and Ricketts’ glassworks on Avon Street in Bristol, exposed the physical remains of some of these innovations, the surviving fabric providing important evidence for the adoption and experimentation with new technology.

Despite being largely absent from the available company records, it was the successful application of this technology that ensured the survival of these two firms into the 20th century.

 

Ian Miller BA FSA

 

Ian has been involved in commercial archaeology since 1989, and is presently a Senior Project Manager with Oxford Archaeology North. His principal area of interest since the early 1990s has been in Industrial Archaeology, and he has been involved in the research, survey, and excavation of numerous industrial sites throughout England. In particular, he has spent many years working on the archaeology of the textile industry, and the associated growth of industrial townscapes in the North West. His knowledge of 19th-century glass furnaces stems from recent excavations carried out by Oxford Archaeology North at the Perciva Vickers flint glassworks in Manchester, and the Powell & Ricketts glass bottle works in Bristol.

Two interesting conservation projects have been identified during the recent treatment of glass objects in the Cleveland Museum of Art and the Ashmolean Museum of Art and Archaeology. The first case is a goblet attributed to Herman Schwinger (German 1640-1683) in the CMA collection. The goblet was treated and then re-housed to impede further the degradation of the unstable composition.

Collections of ceramics, glass and stone have historically been relegated to the least stable storage areas due a lack of resources and the perception that they are consistently robust in nature. Occasionally this exposure has resulted in extreme reactions which can create visible changes within short periods of time. Isolation within an RH controlled container is a preventative measure that can be used in the short term with the aim to impede inherent instability and hopefully prevent any controllable reactions. The treatment of a glass object with an inherently unstable composition and the exploration of practical methods which could be used to isolate objects will be discussed.

The second case is a heavily restored 9th century Iranian jug; the previous restoration was removed and a support fill made for a large area of loss. The jug will be on permanent display in the new Conservation Gallery in the Ashmolean Museum as an example of interventive conservation and accompanied by a brief description of the treatment.

Reference:
“Short-term Storage of Objects
Sensitive to Relative Humidity”
November 2008 issue of ICON News

Dana Norris PGD

Having graduated with a BFA from Kent State University in Ohio, Dana put her experience with ceramics and glass to good use as Artist in Residence at the Watershed Centre for Ceramic Art in Maine, followed by a period working as a Studio Potter in North Carolina. A Post Graduate Diploma in the Conservation and Restoration of Ceramics at the UK’s West Dean College paved the way to a post as Assistant Objects Conservator at the Cleveland Museum of Art in Ohio and most recently the position of Ceramics and Glass Conservator at the Ashmolean Museum of Art and Archaeology in Oxford.