Page 42 - Between light and shade

between light and shade, TRANSPARENCy and reflection

EVA) 0.38 mm transparent films 28. This glazing
also has the advantage of blocking ultraviolet
radiation.

The combination of sheets of toughened
glass 29 and ordinary float glass improves the

28 Laminated glass was invented in 1903 by the French chemist
Edouard Bénédïctus (1879-1930) and was patented by him under
the name Triplex. Nevertheless, it was the invention, in 1927, of
PVB (polyvinyl butyral) by the Canadian chemists Howard W.
Matheson and Frederick W. Skirrow that marked the starting
point for the use of laminated glass for car windscreens, from
1936 onwards in England. We had to wait until the 1960s for
its application in construction, 1980 for the first Belgian “stan-
dard” (an STS — spécifications techniques unifiées (unified
technical specifications)), and 1989 for Belgian standard NBN
23-002.
EVA: ethylene-vinyl acetate was developed in 1950 and marke-
ted by ICI (Imperial Chemical Industries).
29 A pane of toughened glass, patented in around 1930 by Rudolph

Seiden (1900-1965), is approximately two to five times stron-
ger than an ordinary pane of glass as it is pre-stressed by slow
heating followed by rapid cooling of its external surfaces,
which are compressed by the contraction and tension exerted
by cooling on the centre of the sheet. “Reinforced” (wire) glass
invented by Frank Shuman (1862-1918) in 1892 and made up of
a fine mesh of steel wires moulded into the glass, was the first
attempt to provide glass offering a degree of safety. However, as
the steel’s thermal expansion coefficient is twice that of drawn
glass and three times that of borosilicate glass, it is doomed
to fail when subject to repeated temperature variations. This
makes it all the more surprising that it was still being used for
the leaves of fire doors in the United Kingdom until recently. In
addition to their low mechanical strength, and like the majority
of polymers, PVB and EVA are subject to creep, which does not
enable the properties of glass to be fully exploited. This is why
I suggested to AGC, in 2010, that it was necessary to develop
a new type of reinforced glass (owing to the significant recent

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