Glass that changed world invented at Pilkingtons

Alastair Pilkington hit on the brilliant idea of changing the way glass was made as he watched his wife washing the dishes at their St Helens home.As he gazed at a plate floating on the soapy water he wondered whether the same science could be applied to glassmaking.He tried it, and it worked, and the idea earned Pilkington Brothers as it was then called £600m.

Virtually all of the glass made until then was drawn from pots of molten glass, but it contained flaws and bubbles.

From that kitchen sink Eureka! moment in 1952 it was to be another seven years before Alastair Pilkington and his team had perfected the process.

More than half a century later float glass has entered an elite hall of fame for engineering wonders.

The company has been presented with the prestigious Engineering Heritage Hallmark for the invention of the Float Glass process.

The accolade, awarded by the Institution of Mechanical Engineers, which has the Queen as its patron, describes float as "the major glass innovation of the 20th Century" which has had "enormous" social impact.

"Almost all the glass that the public sees or looks through today is Float Glass," says the impressive citation.

The IMechE launched the heritage scheme in 1984 to recognise landmark developments in mechanical engineering and to raise the profile of the profession.

Only 36 awards have been made so far, and previous winners include the Harrier jump jet, the Rolls Royce RB 211 engine, the Thames Barrier and the Jubilee Extension Line.

The Float Glass process was invented by Pilkington in St Helens in 1952 and announced to the world in 1959 after seven years of secret development work in a wooden shed in its Cowley Hill glass works.

Pilkington Group chief executive, Stuart Chambers, said last night: "This award is really a credit to all those Pilkington engineers, and production employees, who worked on the Float Glass project ove years without ever knowing whether it would be a success.

"Their commitment to an objective, despite setbacks on the way, was genuinely outstanding and reflects the best traditions of British engineering."

Sir Alastair Pilkington (no relation to the glassmaking family empire) was honoured with a knighthood in 1970.

Later he became chairman of the company and died in 1995. Until the 1950s quality glass could

only be made by the costly and wasteful plate-glass process, of which Pilkington Brothers had also been the innovator.

Because there was glass-to-roller contact, the glass surfaces were marked. They had to be ground and polished to produce the parallel surfaces which bring optical perfection in the finished product.

The other old process, sheet glass, is made by drawing it vertically in a ribbon from a furnace. It was cheaper to make than polished plate glass but it was unacceptable for high-quality applications because of distortion.

In the float glass process, a continuous ribbon of glass moves out of the melting furnace and floats along the surface of a bath of molten tin.

The ribbon is held at a high enough temperature over a long enough time for the irregularities to melt and for the surfaces to become flat and parallel. Because the surface of the molten tin is flat, the glass also becomes flat.

The ribbon is then cooled down while still on the molten tin, until the surfaces are hard enough for it to be taken out of the bath without rollers marking the bottom surface: so a glass of uniform thickness and with bright, fire-polished surfaces is produced without the need for grinding and polishing.

The cost was far higher than anyone had bargained for, and it took considerable courage for the board of directors to go on supporting Alastair Pilkington.

When he finally made it, they decided to license the process, chiefly to get some income but also in order to ensure that others would not find it worthwhile to research their own technology.

Today, over 80% of the world's flat glass is made by the float process.