Pâte de verre
The term pâte de verre was invented at the end of the 19th
century by the French sculptor, Henry Cros (1840-1907). In
experiments at the Manufacture National de Sèvres, Cros and a
handful of contemporaries rediscovered this technique, thought to
date back to Egyptian times.
To make pâte de verre, glass is ground to a granular
consistency. Different colours of glass, powdered enamels and
metallic oxides are mixed to form a paste. This mixture is then
brushed, poured, or packed into a mould.
The mould is fired in a kiln until the glass fuses together. The
mould is broken away to reveal the glass. The glass can be left
with the matte surface or finished by grinding, cutting and
polishing.
Blown glass
The art of glass blowing has been practiced for thousands of
years though the process and tools have changed little since Roman
times.
In order to blow glass it must be heated in a special kiln to
make it pliable. Once the glass is soft enough, hollow ware is
formed by inflating the glass on the end of a blowpipe. The form is
constantly manipulated by blowing through the pipe, and colour and
shape are added to complete the piece. In a studio all pieces tend
to be free blown, and the work can be completely formed at the
glass maker’s chair. The molten glass can also be blown into moulds
and then finished at the chair.
Engraved glass
There are many techniques that can be used to make patterns on
glass.
Stipple engraving is done entirely by hand. A hard, sharp point,
either diamond or tungsten carbide, is tapped onto the surface of
the glass. The tiny dots that are produced are used to make up the
design.
Point engraving, also called line engraving, involves marking
the glass with a hand-held diamond or tungsten carbide point. The
point, held in the hand or on the end of a scriber, scratches the
surface of the glass.
Sandblasting is an industrial technique in which fine grit is
projected onto the glass at high pressure. It is associated with
mass produced designs, but can produce original results with
hand-cut stencils and hand-controlled cutting techniques.
Copper wheel engraving is a traditional technique where the
glass is cut with a copper wheel or disk, rotated in a lathe. An
abrasive powder in oil is applied to the wheel’s edge. By using
different speeds, wheel sizes and edge profiles a wide variety of
texture and line effects can be achieved. Many engravers now also
use stone and diamond impregnated wheels.
In drill engraving a hand-held drill similar to a dentist’s
drill, equipped with a diamond burr, is used to cut into the
surface of the glass. If water is used to lubricate the cutting
surface a softer, cleaner-edged cut is obtained.
Cast glass
This term covers a wide variety of techniques used to form glass
in a mould. The two most common techniques used in modern glass
making are sand casting and kiln casting.
In sand casting, sand is compressed into a metal container and a
wooden mould (former) pressed into the sand to make a void.
Coloured powders and prepared objects of glass or other material
can be embedded into the void before the mould is part filled with
hot liquid glass. More details can be added before the work is
slowly cooled (annealed) in the kiln.
Kiln casting involves filling a mould with pieces of glass and
heating them together until the glass melts into the mould.