Pages: 26 - 47
Author: Michael Kitt
Text: Glass Survey of an industry
The red hot milk bottles, shown here and on the cover, have just been formed by an automatic making machine. They have cooled off sufficiently to become rigid, and to be transferred on to the conveyor which takes them to the annealing 'lehr'. The process symbolises the growth of an advanced technological industry from roots which are deeply embedded in ancient craft traditions. Today the British glass industry sells £160 million worth of its products a year. In the survey which begins on the next page, Michael Kitt, an industrial officer at the ColD, discusses the importance of design to this powerful industry, and describes the modern skills which mould a material that has fascinated man for 5,000 years.
Photograph by John Garner
Background to a modern industry
Each Corning ribbon machine produces glass envelopes for filament lamps at the rate of 1,100 or more per minute at Glass Bulbs Ltd. Here they are being inspected and packed before despatch for final assembly.
Glass is so transparently anonymous that the shop window draws attention only to the products beyond; the milk bottle only to the liquid contained. But for all this apparent anonymity, glass is as exciting and rewarding as any of the other modern materials. Modern technology, reinforced by experience built up over centuries, has made strikingly apparent the diverse potential of this ancient material, first used 3,000 years before Christ.
Most glass is formed by mixing together silica (sand). soda and lime. Small amounts of other substances are also added. The desirable physical properties of the modern glass product are determined almost completely by its chemical composition.
The mixture is fed into one end of a large heated tank and melted at temperatures varying from 1,200ÝC to 1,530ÝC. After it has been refined and cooled, the glass is drawn out ready to be manipulated by hand or machine. The pliability of the cooling glass enables it to be formed in a variety of ways: it can be blown like a bubble, pressed like butter, moulded like jelly, rolled and cut like pastry, drawn like toffee, or spun like candy floss.
The malleability of this fascinating substance, and the variety of useful properties that it can possess, makes it a challenging and rewarding material for the designer. Its applications are far-reaching and continually increasing, and it has a contribution to make to almost all aspects of everyday life.
£160 million a year in sales The British glass industry has a labour force of about 77,000, and is the third largest in the world. Ranging in size from the family-owned lead crystal factory to huge combines like United Glass, the industry's total sales in 1965 - of which exports represented one sixth - were estimated at £155-£160 million.
Some 74 manufacturers are members of the Glass Manufacturers' Federation (GMF). The federation carries out industrial training
Three basic types of glass
Type Composition (per cent) Applications
Soda-lime-silica silica sand 73 containers
soda ash 15 some table glass
limestone 10 sheet glass
alumina 1 lighting fittings
Borosilicate silica sand 80 ovenware
boric oxide 12-5 chemical apparatus
soda ash 4 5 high voltage insulators
Lead crystal silica sand 55 table glass
lead oxide 33 electronic equipment
potassium oxide 12 optical glass
Of the enormous number of glass types, soda-lime, borosilicate and lead crystall are probably best known and are produced in quantity in Britain. All have small amounts of other chemicals besides those given here.
programmes, encourages sections of the industry to work collectively through the federation to further improve productivity, and establishes a liaison with industries closely allied to glass manufacture.
Generally speaking, today's glass industry is one which supplies glass components and packaging to other industries. The British optical glass industry is a typical example, providing a wide variety of precision made products. Chance-Pilkington, for instance, one of the largest manufacturers in this field, produces over 100 types of optical glass at its modern St Asaph plant, including moulded blanks for lenses and prisms, and shielding glasses for radiation screens. The essential homogeneity of optical glass sets it apart from all other glasses, since it must possess accurately defined and uniform values of index of refraction and dispersion.
Components at home and abroad
With the introduction of the National Health Service, there was a sudden demand for ophthalmic glass blanks for spectacles. Highly efficient and flexible methods of manufacture enabled the optical industry to meet the demands on the home market. In addition, the industry exports millions of blanks annually to Japan at a price cheaper than the Japanese can make them.
The electrical industry uses numerous glass components. Glass envelopes for filament lamps are produced at the rate of 1,100 or more per minute on one of the Corning ribbon machines at Glass Bulbs Ltd. Harworth. Miles of glass tubing are used for fluorescent and other fittings. Blown and pressed components are produced in vast quantities for valves, cathode-ray screens, sealed beam headlamps, vapour discharge lamps, and so on.
The modern British laboratory glass industry uses borosilicate glass to supply standardised equipment that is completely interchangeable, functional and accurate. Laboratory glass plays a vital
A skilled manipulator at Quickfit and Quartz Ltd forming borosilicate glass tubes into a Leibig condenser. Standardisation and interchangeability are fundamentals of modern British apparatus.
part in instruments for fundamental research, mass clinical use and advanced electronic instruments. Laboratory glass pipe lines are used by brewery, food and chemical industries.
Cutting out the variables
The industry has long recognised the value of research. In fact, the whole glass industry is now reaping considerable benefits from research programmes that were begun more than 50 years ago. The first university department in the world for training glass technologists was set up at Sheffield in 1915.
The British Glass Industry Research Association grew out of the activities of Sheffield University and was formed in 1959 to give a consultative service to its 100 or so member firms, and to carry out applied research. The work of the association is extensive. This year, among many other things, it is looking into the performance of furnace regenerator design and is collecting fundamental data for computer analysis on the facts of the heat transfer process in forming containers.
Emphasis on research has led to the industry becoming more aware of the benefits of quality control, and it is developing a more scientific approach to glass manufacture. The slap-happy approach to glass making is disappearing. "In the old days", remarked T. F. Winder, the manufacturing manager of Glass Bulbs Ltd. passing the dials of the automatic temperature control system for a regenerative furnace, "you'd look in the furnace and say 'looks hot enough' or 'no, too cold'." Francis Hurlbut of United Glass also made the succinct point that "Glass making is a series of variables: we are trying to cut out the variables".
The degree to which automation has been achieved in the machine made glass industry for long runs of any single design is one of its most striking features. Raw materials are weighed, mixed and charged into melting furnaces, which are themselves automatically controlled by instruments to give the correct rate of batch-feed, firing and draught. The forming of the finished glass, whether it is in the shape of a container or a flat sheet, is handled by finely controlled automatic machinery. Only with flexible semi-automatic machinery, usually employed for smaller quantities of glass products, and in the hand-made glass industry, does one find the old skills employed in forming the molten glass. Soda-lime glass tubes for fluorescent lighting, made at Glass Tubes and Components Ltd. Two dozen types of glass are used for tubes ranging from 2 mm-65 mm in diameter. Other universities besides the department of technology at Sheffield are carrying out fundamental work, and of course, the larger manufacturers have their own well-equipped laboratories. The largest of these is Pilkington's glass research laboratory at Lathom, which was set up in 1960 at a cost of £2 million. There, 150 graduates are carrying out research programmes and developing the revolutionary float process (see page 41). The recent Queen's Award to Pilkington's, for technical innovation in glass production, underlines the dramatic technological advances that have been made in the British glass industry during the last decade.
The Society of Glass Technology celebrates its jubilee this month with an exhibition at the Sheffield City Museum which demonstrates the great range of achievements in the world of glass that have taken place during the lifetime of the society.
This is the background to an industry with an immense potential spurred on by research and technological developments in some sectors, seemingly cramped and restrained by tradition in others. Technical advances in machine made glass impose demanding and sometimes frustrating conditions on the designers' freedom: with hand made glass, however, the designer has unlimited scope for experiment, governed only by the skills of the glass manipulator and the opportunities that he, the designer is given. The following pages look more closely at the three main sections of the glass industry containers, tableware and flat glass - and discuss the design challenge of changing technical and market conditions.
5,000 million bottles jars a year
Elegant shapes, like the bottles opposite, are increasingly demanded by design conscious food and drink manufacturers. The demand provides a challenge to designers faced with the severe limitations imposed by high speed, automatic production and filling machinery.
The glass container industry in England was created to meet the needs of the apothecary for storing perfumes and oils, and to provide vessels for bringing wine from the cask to the table. The earliest onion-shaped bottles, squat bottles, sealed bottles and the later cylindrical bottles, were produced by hand from raw materials of a high iron content, which gave them their dark green colour. This is the cheapest type of glass and is still known in the industry as 'common' green or 'bottle' grass.
Today, the manufacture of glass containers forms the largest section of the British glass industry, whether considered in terms of tonnage or value of production.
The glass container industry's best customers are the food manufacturers, who account for about one third of the total sales. Drink companies take just under another third, and the remainder is used for pharmaceutical, cosmetic and other purposes. Sales in 1965 are estimated to have climbed to a total of just over 5,000 million units.
The great step forward came in 1908 with the introduction into Britain of the fully automatic Owens glass bottle making machine.
The revolution in glass bottle making led to the widespread use of glass in food distribution, and today 30 million bottles of milk are delivered daily to British homes, schools and catering establishments. The bottles are used repeatedly. The 1/3 pint bottles for school milk are known to average 75 trips and, coupled with beer bottles, which average 40 trips, the total number of bottle trips annually must average 25,000 million.
Glass containers are popular with food packagers for a variety of reasons. Glass is inert to most substances, and the smooth surface and the ability to withstand heat enable bottles and jars to be washed and sterilised effectively, and to take hot filling. The rigidity of the glass container, the consistently high mechanical strength, and the close tolerances within which they are made, allow high speed conveyor belt filling - an important factor when it means that a batch of 800 baby-food jars can be filled and capped by machine every minute. Glass container shapes can also be associated with certain specific products and the transparency of the glass allows for the visual examination of the contents.
Forty years of jam- jars, showing progressive refinement of quality and reduction of weight. Far left, 1920 jar, uneven in shape: Ieft to right light weighting of jars; 1945, 9 oz; 1947, 7 oz; 1960, 5 1/2 oz.
Opposite The Treetop bottles were designed by the Brand Group at Van den Berghs Ltd in conjunction with S. H. Benson Ltd. The design won a Starpack award in 1963.
The disadvantage of glass in packaging has of course been its weight. However, with modern production methods, most containers today have been redesigned to use less glass in their manufacture without impairing their performance. The modern jam jar, for example, weighs only 5 1/2 oz. as against about 13 oz in 1920. Among the many obvious advantages of 'lightweighting' is the fact that the thinner wall section can withstand great thermal shock: strength is invariably increased and yet the required capacities are retained.
The other problem with glass is breakage: now, however, invisible metal-based coatings have been developed which increase lubricity and reduce abrasion, and hence give longer life. United Glass' Titanising process is one commercial example, for which increases of 65 per cent in bursting strength and 71 per cent in crushing strength are claimed.
There are developments in the other direction too: 'one trip' drink bottles that are strong yet light are being produced. Engineered for fast filling lines and designed to fit in with modern marketing methods, they may one day supercede the 'deposit and return' variety. Other developments in packaging include lightweight glass packs of vegetables, which will soon be seen in the supermarkets, and the many 'after use' containers being developed.
As a result of the rapid development of the glass container over the last decade, it has been found necessary to revise the glass containers section of BS 1133 Packaging Code, first issued in 1955, to take into account the many improvements that have been introduced to reduce handling and distribution costs of the glass containers. To sum up, the improvements have led to containers that are lighter in weight, with closer tolerances and of more consistent quality.
Technical limits to design freedom
The designer in the container industry has to work within well defined limits. Apart from production limitations, cost
and the high speed filling lines have to be considered. Squat containers give These single trip bottles are made by
Forster's Glass Ltd to Schweppes' the greatest stability on filling machines, but market appeal demands height end
distinctive shapes: the result tends to be a compromise. The designer must also work with closure manufacturers,
and labelling is an important factor.
From the designer's first sketches, a wooden or plastics model is produced which is assessed and approved by both designer and packager. A pilot mould is then made and three or four dozen containers are produced in glass. These are tested for filling and capping. If all is satisfactory, further moulds are made and the container goes into full production.
With the art colleges' present facilities, the training of designers for the container industry can only be theoretical. Manufacturers advertise for Glass container designers and the successful I applicant has to glean the practical rudiments of container design from the factory floor - very few have even a basic knowledge. It is symptomatic that Forsters Glass Ltd won an Institute of Packaging year for Starpack award this year for an amber glass flagon designed by one of the firm's engineers.
Factory trained designers who have graduated from being apprentices generally tend to produce conventionally shaped glassspecifications. Each weighs 6 3/4 oz. compared with 14 oz for the standard bottles. They incorporate a reseal screw top.
Container cost in pence
Number of trips
Cost per trip in pence
Cost per gallon in pence
The table shows comparative costs of using glass milk bottles and cartons. From The Economics of the Milk Bottle by Rowena Mills.
Glass jars at Crosse and Blackwell Ltd are placed on conveyor belts to be mechanically filled, capped and labelled. High speed filling depends largely on the accuracy of the container's external dimensions, which containers. Overconscious of the limitations imposed by the glass forming machinery, their designs often lack the flair that can be imparted by the man who has had the opportunity at art college to learn to draw and to experiment with making shapes from many materials.
Designing the whole pack
The graphics of label and cap design often detract from the more modern appearance of the glass container. Co-operation between the glass manufacturer and packager, and the use of good graphic designers are needed to make the design standard of both container and label compatible.
Some designers try to achieve this unity by designing everything to do with the container themselves. Paul Hartland, designer for can be controlled to fine limits. Some machines for bottling drinks can fill, cap, label and cover with foil capping, 30,000 bottles an hour.
Jackson Bros Ltd. says he tries to design the whole pack - bottle. label, cap and cartons. He is often handicapped because the existing filling and capping machines allow him no latitude with the size and shoulder contour of the containers; sometimes even old stocks of labels prove a limiting factor.
He was able, however, to design containers in this way for Marela, the London pickle company. The brief stated that the jars should be modern and attractive, should handle well and withstand a variety of processing techniques; in addition they had to label quickly and easily, and be stable enough to pass through high speed filling and capping lines that would be used for several sizes of jar.
He designed the 6 oz. 10 oz and 16 oz jars (illustrated on page 34) to accept common closures, and used identical cap and label designs. The colours of the labels were varied to give immediate
recognition, and to harmonise with the contents of the jar. The backward-sloping surface of the jar is designed to expose the label to the high intensity overhead lighting in a supermarket. The shape allows the filling and capping lines in the factory to operate almost continuously even on different sizes and types of product. The indented shape and the lightness of the container are intended to produce freight economies and greater convenience for shop staff and the housewife. J. J. Rubin, Marela's marketing director, said that "The research which resulted in this packaging was our best ever i investment".
Though not entirely satisfactory visually - the graphics on the label, in particular, are open to criticism - the jars do represent a vigorous attempt at an overall design solution.
Another interesting design is the soft drinks bottle (illustrated on page 31). This won for the designers and manufacturer a Starpack award in 1963. Here bottle and closure have been designed as a unit, and the unbroken line gives the container a satisfying shape. The tapered form is also convenient to use. A measure of unstability resulting from too narrow a base, and poor graphics on the label, detract from what is otherwise a most attractive and functional container.
These two examples illustrate the attempts that are being made to come to terms with the various factors governing the design of this type of glass product. If glass is to keep its position as the foremost packaging material for the food and drink industries, designers and manufacturers must work increasingly along these lines, taking advantage of technical developments and keeping in close touch with the demands of the industries they serve.
Designed by Paul Hartland for Marela Ltd. these jars represent an attempt at a comprehensive approach to container design, in which jar, label and closure were designed to relate to each other.
Tradition or experiment the table glass dilemma
The craftsman in this photograph is making lead crystal glassware in ways which have hardly changed in centuries. But mechanised equipment produces more and more of the glasses we drink from. Both methods create barriers to experiment.
Typical of the lead crystal industry is Whitefriars Glass Ltd. where the 'metal' is gathered from clay 'pots', and is blown and manipulated by a team of craftsmen known as a'chair'.
In 1673, the Glass Sellers Co engaged George Ravenscroft to find a possible substitute for the fashionable and sophisticated Venetian crystal. He discovered that the addition of lead oxide to the then existing glass gave a new lead-alkali-silicate glass of unusual brilliance, known as lead crystal. This lead glass was found to be softer, heavier, clearer and more brilliant than the Venetian sodalime glass, and it led to a new style in glassware from which developed the modern wine glass. The cutting of glass was stimulated by the glass tax of 1746 which taxed glass by weight.
British full lead crystal is produced by nine factories, of which five are in Stourbridge, two near London and two in Scotland. It is one facet of the British glass industry that has not become mechanised, although general working conditions have been greatly improved: melted in clay pots, the 'metal' is blown and worked by hand.
All the factories are small compared with those where the glass is machine made; moreover, their expansion has been checked either through Government restrictions or lack of capital. However, interesting changes may now come about as a result of recent alterations in the structure of the lead crystal industry: affiliation to larger glass manufacturing groups has favoured the injection of capital and up-to-date marketing policies.
The frustrations of tradition The British lead crystal industry currently finds itself in a quite understandable dilemma. On the one hand, the popular demand for traditional, hand-made cut crystal tableware, both on the overseas and home markets, fully absorbs the output of the present skilled labour force. On the other hand, the industry itself is aware of the need to allow its trained designers to forge ahead with new designs based on its rich tradition. The present trend towards general simplicity in furnishings does not help an industry fully equipped to manufacture magnificent traditional products, and the very nature of British full lead crystal, with its striae and seeds or minute bubbles, requires a cut decoration to make it acceptable to the user.
Many company buyers, too, become indignant when new designs are introduced while long awaited deliveries of existing lines are not forthcoming. Commenting on this problem, John Webb, of Webb Corbett, remarked that "The market has a picture in its mind of the glass industry as suppliers of a traditional product". G. Stuart of Stuart Crystal amplified this: "A manufacturer's idea of good design is first a saleable one and second a creditable design." There are other problems too. Mr Stuart went on to say that "the demand for present designs is more than sufficient to keep us going, but we must export to live and orders are coming too quickly. We are starving the home market with 40 per cent of production - 60 per cent goes overseas". The industry has realised that too many ranges of traditional designs are being offered but, on the other hand, it has been said that the more factories standardise their
ctories standardise their ranges of glasses, the less opportunity the blower and cutter have to practise.
This soda-lime vase from the Lochalsh range is an example of the modern, elegant designs made by the Caithness Glass Co Ltd. It is cased glass in a range of subtle colours. 10 inches high, £2 9s 6d.
Hand made bowl in full lead crystal with cut and polished decoration. It was designed by David Queensberry for Webb Corbett Ltd and is available in 7, 8 or 9 inch diameters. From £7 13s 6d.
Whitefriars Glass Ltd. however, has experimented successfully with modern coloured and colourless lead crystal designs. Other firms, too, are developing new ideas. The Duke of Edinburgh's Prize for Elegant Design went in 1964 in 1964 to David Queensberry for a prestige range of cut lead crystal vases made by Webb Corbett Ltd. and Caithness Glass, a comparative newcomer to the industry, has made a bold attempt at simple, elegant shapes.
Hand-made functional shapes in soda-lime glass have been designed by R. Stennett-Willson and made by Nazeing Glassworks Ltd for large commercial users; the Pullman service for British Rail is one example. Mr Stennett-Willson has planned a completely new factory at Kings Lynn and this will be in operation in 1967, producing simple new designs by hand in both soda-lime and lead crystal.
Modern cut full lead crystal wine suites are gracing the tables of modern British embassies in Belgrade, Lagos, Accra and Warsaw. Thomas Webb's Envoy suite, commissioned by the Ministry of Public Building and Works from a design by Professor Robert Goodden of the Royal College of Art, illustrates how full lead crystal can take its place in the modern way of life.
For dining room and pub The machine making of table glass was developed at the turn of this century. The early pressed glass imitations of lead crystal designs have given way to machine blown or pressed glassware that takes full advantage of automatic techniques.
A large percentage of machine blown glass is supplied to breweries and caterers, and has become associated with the 'pub'. But new and more elegant designs are now being aimed at the retail market and these will no doubt have a wider appeal as the hand-made product of the lead crystal industry becomes inevitably more expensive. Recent advances in moulding techniques have made possible the production of these more elegant designs. The qualified designer can now work to within tolerances of 0 001 inch, ensuring better detailing of the finished product, exact capacities, and control over the weight of glass used.
From the designer's original sketches, accurate drawings are made. Then models are turned in wood or plaster, and any moulded decoration carefully carved. At this stage, modifications to the original design are carried out after consultation with the manufacturers. Designing glass has to be more than one man deep, and the designer must have the co-operation of the pattern maker, the mould maker and the sales team. The trained man can drastically reduce production costs by designing glass shapes for the making process, and incorporating, where appropriate, the use of block instead of multi-part moulds.
A new range of table glass designed for the automatic machineblown process must have a run of several years to justify the high tooling costs. A set of steel or cast iron moulds that will form the new glass shapes is produced for each machine, together with duplicates to replace the original moulds as they begin to wear out. It can cost several thousand pounds to make a pattern from the designer's finished model, produce a block mould and mill the making mould. Depending on the quantity of glass produced, it can take between one and five years to recoup the investment.
Williamson, consultant designer to United Glass Ltd and Johnson and Jorgensen Ltd. remarked that some designs he did some 20 years ago were only just becoming best sellers.
The designer has to consider all these factors carefully as he proceeds, and Mr Williamson believes that the consultant quite often has the edge over the staff designer, who continually works under pressure and has to 'knock a design out'. A design for table glass that has to withstand the test of a long production run should be quietly and carefully evolved and all the problems worked out in detail with the production team.
New processes offer further challenges to the designer of tableware. Silk screen decoration, for instance, on glass tumblers is becoming popular, and the machine cutting of soda-lime glasses is improving in technique. This latter technique needs careful handling by a designer who can design for the process.
Clear and opal borosilicate glass, able to withstand thermal shock, is now machine pressed into shapes suitable for oven-to-table use. Some of the clear glass casseroles are good examples of design for mass production but, on the whole, the standard of opal glass tableware is not high. Lithographic patterns have been used which have tended to imitate the cheaper designs used by many earthenware potters, and there has been little fresh thought either in the opal glass shapes or patterns. If the design of the product were to be improved, it could appeal to a much more discriminating public and not only to the low price market at which it has generally been aimed.
Hand-made in c/ear glass, the Tower Service range, in six sizes, was designed by R. Stennett-Willson and made by Wilmart Ltd. Beer goblet, 7s; goblet, 5s 9d; c/ares glass, 5s 3d.
Examples of soda-lime Dema Glass made by Glass Tubes and Components Ltd. They are machine-blown in one piece, avoiding the join between stem and bowl. Prices from about 1s 3d.
Hand-made, crystal carafe, tumblers and vase from Whitefriars Glass Ltd. Carafe, about £1 7s 6d, and tumblers, £3 14s per dozen, designed by W. J. Wilson. Vase, about £2 10s designed by Geoffrey Baxter.
Five Star, machine made soda-lime glasses from Ravenhead Glass, designed by Hardie Williamson and distributed by Johnsen and Jorgensen Ltd. Prices from about 2s 9d.
The Phoenix casseroles in borosilicate heat resistant glass were designed by Peter Glynn Smith for The British Heat Resisting Glass Co Ltd. Prices: 1 1/2 pint. 8s 5d; 22 pint, 10s 3d; 3 1/2 pint, 13s 6d.
Revolution in flat glass
Most of us think of flat glass as the stuff that goes into the window frame at home. But technical developments of all kinds are revolutionising the uses of this material, and are providing architects and designers with exciting opportunities.
Sheet glass emerges continuously from the top of the annealing tower, where it is automatically cut, snapped off by operatives wearing protective clothing, and removed by hydraulic handling equipment.
The diagram of the float glass process shows how the ribbon of glass is drawn from the furnace over a tank of liquid tin at controlled temperatures, after which it passes to the annealing 'lehr' and is
The manufacture of flat glass, needed of course in vast quantities for building purposes, is an important section of the industry, and one which has recently seen one of the most striking developments in the history of glass making. The British invention of the float glass process has revolutionised plate glass manufacture throughout the world, and today it has almost entirely superseded the long and expensive method previously used. Now a highly advanced yet constantly changing manufacturing method, it was announced by Pilkington's in 1959. The cost of developing the process was £4 million; by 1965 this sum had been recouped in licensing fees.
In the float process, the basic materials are processed as for polished plate - ie melted together in a tank - but then the molten glass is floated in a continuous ribbon on molten tin at controlled temperatures. Pilkington's states that "the finished product is completely transparent: the two surfaces of the glass are flat, parallel and fire polished, giving clear, undistorted vision, reflection, and a natural unspoiled surface with a brilliant lustrous finish. Float glass, therefore, combines the finest attributes of sheet and clear
subsequently cut to size. The photograph shows the nearly 12 ft wide ribbon of float glass as it comes from the lehr at Pilkington's Cowley Hill works at St. Helens.
plate glass." The time-consuming grinding and polishing operations have been eliminated, cutting the production time by half and consequently reducing costs considerably.
Alastair Pilkington, leader of the team which worked on the float glass project, ended the speech he made when he was presented with the 1963 Toledo Glass and Ceramic Award with encouraging words about the future: "The commercial problems are not easy to see, but from a technical point of view the process shows all the signs of becoming a universal method for the making of flat glass. The process is moving rapidly in this direction; in fact the rate of development is almost embarrassing as plans are continually being upset by new possibilities. We expect great things from the float process in the future."
The advantages of the process were soon recognised by glass companies throughout the world. The largest manufacturers in the USA, Europe and Japan have now been licensed to produce float glass. Discussions are now in progress for the granting of a licence to Czechoslovakia. Pilkington's itself is building a $20 million float
Glass: survey of an industry
plant in Canada: this will begin operating in 1967 and will make the Canadian glass industry one of the most modern in the world.
Sheet or window glass for ordinary uses is still vertically drawn in a continuous ribbon of treacle-like consistency from a tank containing up to 1,200 tons of molten glass at temperatures varying from 1,200ÝC to 1 ,530ÝC. It is snapped off at the top of the annealing tower at the rate of 50 miles or more a week. The resulting fire-finished vitreous surface is good, but the glass is seldom free from distortion as both surfaces are not perfectly parallel.
Glass in architecture Developments in sheet glass have increased its value to the architect, engineer and designer. The special types of flat glass now available enable larger areas of glass to be specified in modern buildings. Heat absorbing glass which cuts down the effect of the sun's rays is used in modern airport control towers. Amber tinted glass forms an effective deterrent against house flies in food stores, and coloured opaque glass can be used to provide hygienic walling in operating theatres.
Complete building facades can now be formed from a suspended assembly of toughened float glass. A new method of glazing allows the architect to use the glass itself as a load-bearing material without the use of mullions Airframes of any kind. Toughened glass fins, - inch thick in the form of cantilevers, stiffen the assemblies against wind pressure. Probably the largest suspended toughened glass assembly in the world, weighing 130 tons, is currently being produced by Pilkington to enclose the 800 ft long frontage of the grandstand and clubhouse of America's Laurel Park racecourse in Maryland.
A new 'super grass' that can be mixed with concrete or plastics to give them exceptional strength has just been discovered by a team led by Dr E. M. Nurse and Dr A. J. Jajumdar at the Building Research Station. This glass reinforcement should bring about significant design changes in building structures, since it is now possible to use thinner, stronger sections.
Double-fixed glazing, such as that used in the CIS building in Manchester, gives airtightness and enables a high degree of sound insulation to be achieved. It also gives controlled, ducted ventilation and a precise temperature. For private houses, hermetically sealed, double-glazed units are factory produced in many stock sizes, and now an allglass unit can be glazed into many existing frames.
The decorative use of glass in architecture must not be forgotten either. Stained glass has for centuries had an ecclesiastical association, but today its modern derivations are used by artists and designers to give important buildings 'eyes' with decorative glass effects.
From the 'antique' glass and 'Norman slabs', slab glass has recently been developed. One inch thick, faceted and shaped, it can be set in concrete or resin, and the designer can vary the thickness of concrete between the 'lights'. Slab glass is particularly suitable for modern secular building; its decorative qualities enrich the exterior wall surface, and from the interior the thick faceted glass refracts the light with jewel-like brilliance.
Whether the building is secular or ecclesiastical, it is vital, text continued on page 44 Well over 50,000 sq ft of 4 inch float glass was used in glazing the first 15 floors of the CIS building in Manchester. Architect, G. S. Hay in association with Sir John Burnet Tait & Partners.
An example of a new technique of fusing overlapping pieces of coloured glass to form a decorative panel of uniform thickness. Designed and made by Keith Cummings at Whitefriars Glass Ltd.
The entire window area in front of the pillars in the offices of Brown & Polson Ltd. Esher, is a single, suspended assembly of 16 armour plate glass panels. It incorporates vertical stiffeners..
This window in Manchester Cathedral was designed by Margaret Traherne. It is a war memorial, and the glass, set in the original medieval framework, expresses the fire of battle and sacrifice.
Glass: survey of an industry
The windscreen of this car has a wide section stressed in a non-uniform way. On impact, this section will break into bands of large which can still be seen through, however, for the glass designer to work closely with the architect at the planning stage to ensure that glass becomes an integral part of the design. Far from providing purely a background, fused coloured glass, flashed glass, etched, engraved and sandblasted glass, glass applique, glass mosaic and abstract colour glazing can make an important contribution to a building.
All these techniques are being used by established artists, and by the designers and students of the lively stained glass department at the Royal College of Art, under the guidance of Lawrence Lee. They are rediscovering that glass, apart from its inherent beauty, is itself one of the most exciting materials. The effect of light, restless and
variable, gives glass a quality of beauty and purity which is both profound and deeply satisfying.
Safety in strength
Clear float glass can be toughened by cutting it to shape, heating it to its softening point and then chilling both sides simultaneously with compressed air. This gives a pre-stressed glass. Because it is then able to withstand heavy strain or loading, and thermal shock (it has been tested through a temperature range of minus 70ÝC up to 295ÝC without being affected), it can be used in circumstances where ordinary glass would fail. Should the toughened glass break under impact, it fractures into comparatively small, harmless particles.
Today, all automobile windscreens are either toughened or laminated using poly-vinyl-butyral. The strength of the glass allows the automobile designer to improve the driver's visibility by incorporating larger areas of glass: at the same time its behaviour under impact gives a measure of safety from laceration in the event of a crash. Zone toughening of windscreens, a further modification, has resulted in improved post-fracture vision.
Other forms of toughened glass have been developed for various special uses. Laminated 'bandit' glass, containing thicker plastics film, is virtually impervious to vigorous attack and is used by banks and jewellers and in certain security vehicles.
In most aircraft windows, the glass components are toughened before being laminated together, and a gold film, two ten-millionths of an inch thick and quite transparent, is incorporated. This is able to accept power inputs capable of de-icing the glass.
These are just a few of the many developments in the flat glass section of the industry: constant research and experimentation, opening up new possibilities, is continually increasing its value to a variety of industries.
Looking ahead at glass design and technology
Training designers for the glass industry can be a frustrating business-not enough openings and too little scope for experiment, say the teachers. Developments in technology provide the most exciting prospects. The two could go hand in hand.
There are three colleges of art in Britain with glass furnaces for training purposes: the Royal College of Art in London and the colleges of art in Stourbridge and Edinburgh.
The RCA has recently combined the smaller school of industrial glass with the school of ceramics, thus giving the students a broadly based training. Students take a general course in the first year and are encouraged to use both glass and pottery. They then specialise for a further three years. David Queensberry, professor of ceramics and glass, believes that many exciting shapes can be achieved by turning other materials on a lathe. "We should develop a new, more experimental approach. Early coiled glass and that made by the lost wax process is so infinitely more exciting than anything that's been made since. When one talks of fine glass, the industry thinks of lead crystal, but it's not the great contribution to the history of glass making. The sooner we move off into other realms of glass, the better". He feels that, while student design at the RCA is competent, "It's not exciting enough yet."
Helen Turner, head of glass design at Edinburgh College of Art, declares that "We aren't going to produce more designers to design noughts and crosses for the cut crystal factories". She felt rather as Professor Queensberry, that "Until the crystal industry jolts itself out of its complacency, then nothing will happen; it needs to do something it's never even thought of before". She thought that the two years' general followed by two years specialised training in glass design which Edinburgh provides, is inadequate to fit a designer for the needs of the glass industry. A postgraduate training was also required. "In Czechoslovakia, they train glass designers seriously. They start at 12 and do six years study."
At Stourbridge College of Art, in the heart of the lead crystal industry, students follow the new DipAD course. Besides the fulltime students, industrial apprentices attend evening classes. The evening students, however, tend to lose interest, and Rene Stevens, head of glass design, would like to see better facilities for trainees within the industry: "The work is hot, hard and physical, and apprentices spend much time on mundane work. Apprentices should be trained to make everything, not just be attached to one 'chair' [the trade name for a group of men pooling their skill to produce glass products]. Caithness Glass sent its boys to Stourbridge for six weeks at a time to train in all aspects of glass making and they are useful to the firm as soon as they leave here."
Designers at Stourbridge College are trained not to become craftsmen but to have a proficient knowledge of the techniques of
David Queensberry, professor of ceramics and glass at the Royal College of Art. "More experimental approach needed ".
Helen Turner, head of glass design at Edinburgh College of Art. "No more noughts and crosses for cut crystal factories".
Irene Stevens, head of glass design at Stourbridge College of Art. "The work is hot, hard and physical".
Glass: survey of an industry
Dowglaz decorative glass tiles are available in various colours, size 10 x 2 inches. Designed by William Mitchell and John Shepherd, they are made by John Dowell and Sons (GBM) Ltd. From 4s each, ex works.
Experimental car designed and made by Ogle Design Ltd for the Triplex Safety Glass Co Ltd. The extensive window area uses a greenish glass which increases absorption of ultra-violet and infra-red rays, thus reducing transmitted radiant heat but only marginally reducing thermal light transmission. The car also has invisible wire heating elements in the rear window and windscreen; the body is glass fibre.
glass making. Besides supplying designers for the local industry, it trains them in decorative techniques that can be applied architecturally. The college realises that the present glass industry can absorb only a limited number of trained designers and that future students must therefore have a broader basis of training and a proficient knowledge of other forms of three dimensional design.
The Glass Manufacturers' Federation has organised seminars for designers in the glass industry, dealing with such subjects as the design of glass containers, quality control, and weights and measures. These have enabled designers from various branches of this complex industry to meet and exchange ideas, and learn about developments in other industries.
A ceramics, glass and mineral products industry training board was established by the Ministry of Labour in July 1965, under the 1964 Industrial Training Act. The director of this board came from Pilkington's, and the GMF's training officer has been appointed as the board's senior training officer. The federation will continue with certain training work, which is carried out in co-operation with the unions, and will collaborate fully with the board.
As in other industries, takeovers and mergers are under way and large groups of companies are emerging with vital capital to reinvest in modernisation programmes. Associations with overseas companies have been formed: one recent example is the link up between the Perkin-Elmer Corporation, the foremost American company in the design and manufacture of advanced optical and electro-optical systems, and Pilkington. The two firms formed a new company in May this year, operating at St. Asaph. It will benefit from the technical knowledge developed in America for highly advanced research, and specialised optical-electronic equipment, laser-optics and tracking devices will be manufactured.
Other interesting developments are taking place. Some of the most sophisticated uses of glass include fibre-optics where bundles of thousands of very fine, parallel glass fibres are capable of transmitting light and images around corners. Here there are obvious medical design applications. Fine glass beads, called ballotini, embedded in plastics, make highly reflective road signs. Light/ energy stored in laser glass can give a very intense beam which already has many uses, including ophthalmic surgery. Designers have used special glasses to form micro-miniature electronic components of great reliability for computer development, and all glass delay lines can, for example, act as 'memories' for computers. Glass ceramics or pyrocerams, designed to withstand great extremes of temperature, are being used for the nose cones of inter-planetary rockets.
These exciting examples of the new uses of glass developed by both designer and technologist are a foretaste of the contribution which this old man-made material can be expected to make to future progress. However, the breakthroughs of the future, which seem to be the ultimate, soon become the applications of the present; their value recognised, accepted and then expected.