Page 33 - Between light and shade

Light, transparency and reflection

produced only with perfect flatness without the
“materiality” provided by drawn glass, which
is able to reveal its presence under light, requi-
ring it to be “marked” where there is a risk of
bumping into it.

The improvements made to float glass, desi-
gned to curb excess energy consumption and
the discomfort resulting from the fashion for
extensively glazed curtain walls, increased this
impairing effect. The quest to reduce the total
amount of energy that glazing allows to pass,
in terms of incident solar energy 14, resulted in
tinted heat absorbing glass and reflective glass
with “vacuum” or “pyrolytic” coatings 15, in all
colours to suit the architect’s wishes.

of concordance between the coloured appearance of an object
illuminated by a given light source (or naturally through
glazing) and the appearance of this same object illuminated
by a reference source with the same colour temperature (or
naturally).
14 The solar factor (S.F. or “g”, which is expressed as a %) defines

the relationship between energy passing through the glazing
and incident solar energy. g = 84% (and LT = 88%) for 6 mm
ordinary single glazing , g = 74% (and LT = 79%) for 2 × 6mm
ordinary double glazing, and can fall to g = 16% (LT ≤ 20% !)
for coated glass.
15 The development of glass with thin coatings began in the 1960s.

Vacuum coatings are applied by cathodic arc deposition aided
by a magnetic field. This is a nanotechnology, which does not
yet have its own name (as it has been referred to since the 1990s)
as these coats are between 10 and 800nm thick (nm = nano-
metre = 10 -9 m = 10-6 mm = 10-3 µm).

33