Architecture

Float Glass – Absolutely Flat

Glass has fascinated all of us due to its brilliant properties- one, that it is weather proof and second, we can see through it. None of the building materials match these natural properties of this wonderful material; it is synonymous with smoothness.

Though the composition of this product has not changed largely through the years, there has always been a fight for perfection amongst manufacturers; perfection in smoothness and its optical quality. These two variables would always define the future of glass.


Initially glass was produced by pouring the molten glass onto large tables, then rolled flat into plates to provide even thickness, cooled, ground and polished before being turned over and given the same treatment on the other surface. The process gave the glass the name Plate Glass.


Plate glass manufacturing was industrialized in 1917 when Belgian engineer Emil Bicheroux developed a process whereby the molten glass was poured from a pot directly through two rollers. This resulted in glass with a more even thickness, and made grinding and polishing easier and more economical.

Another Belgian engineer named Fourcault was working on a different process and he managed to draw vertically a continuous sheet of glass of a consistent width from the tank. Commercial production of glass using the Fourcault process eventually got under way in 1914. The process named this glass as Sheet Glass and it does not required and grinding and polish, making it much cheaper than plate glass.


The above two discoveries made glass an industrial product, rather than a product of craftsmanship. Glass, once used only for castles and cathedrals, was now easily available at low cost. Architects were using it more frequently and the demand grew. As major amounts of glass were still being utilized in buildings, the bigger sizes and good optical qualities were always the foremost requirements. Thus began the war for perfection.


Though sheet glass provided brilliant finish and did not require any grinding and polish, both maintained the same share in the market because of the good optical quality of plate glass. However, the demand for plate glass was growing day by day.

Pilkington Brothers was the Britain’s glass manufacturing company that always looked forward towards better quality and mass production technology. It was a hard time for them as Belgium and France were the most popular glass manufacturers. In that environment of cut throat competition, Pilkington Brothers was able to survive because it was the only plate glass manufacturing company which also manufactured sheet, rolled and cathedral glass, all of which continued to yield profits which balanced the difficulties in the plate market. However, Pilkington had also been able to achieve comparatively low manufacturing costs in plate glass, resulting from numerous innovations and improvements in manufacturing since the introduction of the process.


As there was more demand for plate glass due to its better optical quality, in 1935 Pilkington developed the 'twin' machine which ground both sides of the ribbon of glass simultaneously. These developments gave Pilkington an international advantage in plate manufacture which they shared, however, by licensing the continuous and the 'twin' grinders to overseas manufacturers.

After the World War II, Pilkington Brothers became one of the world leaders in glass manufacturing. But to remain a leader they had to be innovative. Hence, the company was always looking for new talent for their technical department. They had one young energetic boy named Alastair Pilkington (there was no family connection however). His natural instinct always provoked him to look for better solutions over the current process.


Born in 1920, Alastair Pilkington was educated at Sherborne School and Trinity College, Cambridge. He became an officer in the Royal Artillery just before the outbreak of World War II, and later fought in the Mediterranean, where he was taken prisoner after the fall of Crete. When the war ended, he returned to Cambridge and gained a degree in mechanical science. After completing his degree he joined Pilkington Brothers as a technical officer in 1947.

By the start of the 1950s Pilkington Brothers had almost stopped manufacturing sheet glass and was concentrating on manufacturing plate glass due to the increasingly high demand of the latter. Alastair became Technical Director by that time and was continuously thinking about the solution. He saw two major problems in continuous plate glass manufacturing. The process however allowed glass of virtually any thickness to be made non-stop, but the rollers would leave marks on both sides of the glass, which would then need to be ground and polished on both sides.


The other problem was that polishing and grinding rubbed away around 20% of the glass, and the machines were very expensive. Alastair thought that if these problems could be eliminated, the cost would be reduced; a process where glass could be made without rollers like sheet glass but with perfect uniform thickness - that is, absolute flat glass. How to achieve this? The answer was blowing in the wind.

While he had identified what he wanted, his conscious efforts to develop a process to achieve it were disrupted. Being the technical director, he had to give his time to the routine functions. However, he found his regular job boring and often spent his time thinking about how to create a polished flat glass without distortions.

Like many other discoverers, the flash of insight that solved the problem dawned on him when he was not consciously attending to it. One day while helping his wife in the kitchen to wash dishes, he was struck by what he saw. Eureka!


The idea that a flat, polished finish could be produced came to him as he watched the oil floating on the water in the sink. To pour molten glass onto a bed of liquid was a direct corollary of this insight.

He knew that the surface of liquid is perfectly flat, flatter than any man-made surface. The liquid could not be water, it had to be something else. He made three prerequisite variables for this material. It should have more density than glass so that glass could float, it had to melt at a temperature less than the hardening point of glass (about 600° C) and could not boil at a temperature below the temperature of the molten glass (about 1500° C). The best material he found for the job was tin, a metal.


The rest of the concept relied on gravity, which guaranteed that the surface of the molten metal was perfectly flat and horizontal. Consequently, when pouring molten glass onto the molten tin, the underside of the glass would also be perfectly flat. If the glass were kept hot enough, it would flow over the molten tin until the top surface was also flat, horizontal and perfectly parallel to the bottom surface. Once the glass cooled to 600° C or less it would be too hard to get marks and could be transported out of the metal bath by rollers.

In 1952 he prepared a report and presented it to the Board of Directors. The idea was novel, but could it be transformed into reality? Despite knowing that it would cost 2 million dollars just to experiment and to see whether it was possible, the Board agreed to go ahead because of the strong conviction that Alastair had.

Within weeks the pilot project was set up and Alastair produced a seemingly unachievable smoothness to glass, through a float process. The glass was named Float Glass. In 1955 Alastair convinced the company to set up a full scale plant and within 3 years plant was commissioned.




However, it took Alastair fourteen months of non-stop production before the plant could produce any usable glass, costing the company £100 000 a month. Furthermore, once they succeeded in making marketable flat glass the machine was turned off for servicing to prepare it for years of continuous production. When it started up again it took another four months to get the process right again. They finally succeeded in 1959, having spent almost 7 million pounds and announced their accomplishment to the world.

It was a big breakthrough in the glass industry achieved by a team of great engineers and a visionary company, Pilkington Brothers. The company that was on the verge of financial ruin while producing a float glass technology, finally came up as a leader. It later provided a license to many companies. Income from licensing and technical fees was running at a rate of £30 millions a year in 1986.


Alastair Pilkington encountered numerous setbacks during his seven years of hard labour. People, he recalled later, kept asking him: "When will you succeed?" All he could say was: “We will know the answer to that only when we have succeeded.” The cost was far higher than anyone had bargained for, and it took considerable courage for the Board of Directors to go on supporting him.

Alastair Pilkington's endeavors, all those years ago, could have led to disaster. But his persistence paid off. It is one of the most remarkable success stories in British industry. Alastair was honoured with a knighthood in 1970 for his contribution and three years later in 1973 he became Chairman of the company. Alastair died on 5th May 1995. The modern glass industry owes much of its heritage to this man.


Today around 800,000 tons of float glass is produced by 260 plants all over the world. Many of these plants can produce 1000 tons of glass every day continuously for 15 years before they require any repair.

“A large part of innovation is, in fact, becoming aware of what is desirable. (Then you) are ready in your mind to germinate the seed of a new idea...” – Alastair Pilkington

from CBS forum

posted by noobs @ 5:21 AM