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The Fascinating Story behind Float Glass Manufacturing

April 9, 2018

As we all know, clear float glass is a sheet of glass which is made by floating molten glass over a molten metal bath in order to achieve an end product of uniform thickness and a smooth surface. Float glass is, therefore, one of the most basic forms of architectural glass and can be processed further to yield functional variants of glass such as tempered glass and laminated glass.

But, behind all these technicalities, there lies a fascinating story of how the perfect technique for float glass manufacturing was discovered. It was in 1959 that Sir Alastair Pilkington from Merseyside, England, discovered the innovative process that is followed till this date. And it was all a result of a serendipitous sight.

Before the discovery by Pilkington

Till the 1600s, glass continued to be made by blowing large cylinders of hot glass which were then cut and flattened into sheets. Thereafter came the techniques of making plate glass (in which molten glass was poured into a mould and pressed in between plates to create a flat sheet of glass) and sheet glass (in which ribbons of molten glass were extracted from a furnace and flattened by passing them between rollers). Both these techniques were time-consuming and a costly affair, not to mention the surface imperfection and inferior quality of the resultant glass.

How to make glass which is perfectly flat, smooth and clear was the question on every glass manufacturer’s lips till the 1950s. One such manufacturer was Alastair Pilkington, who later on received his knighthood for the invention of the float glass manufacturing process.

A ground-breaking invention

The Pilkingtons were already known for inventing the plate glass manufacture technique. But the need for a better glass manufacturing technique that could produce glass of the perfect quality was always high on their agenda.

As the story goes, in 1952, while doing the dishes one night, Alastair Pilkington happened to notice one of the dinner plates floating on the water surface in the sink. Instantly, it struck him: what if he could float the glass ribbon from the furnace on a similar liquid surface? The molten glass would mirror the flat liquid surface and will settle down evenly due to gravity!

The only obstacle that remained was finding the perfect liquid for floating molten glass. Water, for all its abundance, would have instantly vaporized upon coming in contact with glass at such a high temperature. Thus, for seven long years, Pilkington and his scientists continued to experiment until it was discovered that molten tin offers the best liquid surface for float glass. The molten tin bath allowed the glass ribbon to cool down slowly while floating, and could also be separated from the cooled glass without leaving any mark on its surface!

Thus, the Pilkington process was born, and float glass of zero distortion, perfect thickness and amazing clarity could be mass produced. This very process is what is used in the manufacture of AIS Clear Float Glass as well.

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