With Light: Tools & Techniques
process of colouring was largely a chemical one in which metal
oxides (copper for red, iron for green, cobalt for blue) were
fused with glass under great heat.
was a 12th century glass painter, Theophilus, in his work 'On
Diverse Arts' who first explained the practical techniques little
changed over the centuries: "…if
you want to assemble simple windows, first mark out the dimensions
of their length and breadth on a wooden board, then draw scroll
work or anything else that pleases you, and select colors that
are to be put in. Cut the glass and fit the pieces together with
the grozing iron. Enclose them with lead cames...and solder on
both sides. Surround it with a wooden frame strengthened with
nails and set it up in the place where you wish…"
the early Middle Ages, glass was expensive as it was rare, and
made only in small quantities. It was provided
who usually set up shop at the edges
of forests where sand for glass making, and wood for the kilns,
could be easily obtained.
at the construction site, glaziers cut the raw sheet glass into
pieces used in creating the windows. First,
the subject of the panel was agreed upon by the donor of the window,
from which a
glazier would prepare a sketch. This then became a full sized
"cartoon" and transferred to a large bench that served as a template
for assembly. The
template included all the calmes lines (the lead) which were,
in turn, shaped to the pieces of glass that made up the painting.
red hot iron was used to cut a rough shape, with a final cut made
by a hooked shaped tool - the grozing iron. Then the actual painting
of each piece of glass was completed, with
lines and shading done in black. Finally,
pieces were fired in a kiln to fuse the design to the glass. The
final assembly was done back on the table, with larger panels
supported by iron saddle-bars to strengthen them.
Since bigger windows were more costly, increasing
use was made of a clear or grey glass with simple repeated designs
known as grisaille (from the French, for grey).
being cheaper, grisailles made interiors even lighter, albeit
less dramatic. A later addition to the glazier's pallet was silver
stain which resulted in colors from light yellow to a warm gold.
whole process - from conception to final installation - took many
highly skilled craftsmen, working under the watchful eye of the
master glass painter...
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