Stained
glass is the broad and encompassing term used to describe various
kinds of glass cut into shape, to form designs. Joined by lead,
copper, foil or cement; this glass creates an ever-changing relationship
with light. Since stained glass has the capacity to both transmit
and reflect light, the interplays of strong colours, intense light,
soft hues and subdued illuminations evoke moods and emotions. Light,
the changing element, in its brilliance stimulates the reds and
golds; when muted by clouds, it enhances the blues and greens. Light
creates an ever-changing palette of colours.
How is the glass made?
Glass
is made from silica sand with iron, limestone, soda ash and borax.
These elements are heated at a temperature of approximately 3000°
F until it is a liquid. When the glass is cooled, it hardens to
become what we commonly call glass.
Sounds
simple, right? Well, the process is a little more complicated than
that. There are many different kinds of glass, and many different
processes that give it texture and colour.
Antique
glass
is formed by hand in a process called glass blowing, where the
glass maker blows air through a tube to shape liquefied glass
into a cylinder. These cylinders are cut and melted into flat
sheets. Antique glass is rich in variation. The thickness of the
glass can vary from one end of the sheet to the other. It may
contain air bubbles, known as seeds, or other striations,
each of which adds to its character and enlivens it as light passes
through.
Cathedral glass
is not mouth blown, it is usually machine made in flat uniform
sheets. Its consistency makes it a wonderful choice for larger
projects. This glass can come in a variety of textures
and imprints. Texture is a
very important feature in most stained glass work. It helps to
create contrast and interest, while increasing privacy and security.
Can
you guess which glass is more expensive? Antique is costly because
of the large amount of skill and time involved in making it.
How
does glass get its colour?
A common misconception is that stained glass is merely window
glass that has been coloured with dye or paint.
The colour of glass is determined by the chemical make up of its
ingredients. Minerals and metal oxides are combined with the molten
mixture to produce the desired colour. A glassmaker adds different chemicals
depending on the desired colour:
- Selenium or gold salts for reds and pinks
- Cadmium for yellows
- Copper oxides and cobalt for blues
- Sulphur for ambers
- Dichromate or iron oxides for greens
- Manganese oxides for purples
For example, in antique windows the depth of the reds would vary depending
on the availability and the cost of gold.
Colour
can be painted on to the surface of the glass but for sustained
longevity the glass must be heated in a kiln so that the
paints are fused to the surface of the glass.
