History of Stained Glass - 2
Stained glass has been produced since ancient times. Both the Egyptians and the Romans
excelled at the manufacture of small stained glass objects.
The term, stained glass, refers to glass that has been coloured by adding metallic salts during
its manufacture. Painted details and yellow stain are often used to enhance the design. The
term also applies to windows in which all the colours have been painted onto the glass and
then annealed in a furnace.
The manufacturing of stained glass started in the 10th century. It was then that stained glass
began to flourish as an art. Glass factories which had a ready supply of silica began to spring
up. Silica is essential to the production of stained glass. Glass was coloured by adding
metallic oxides to the glass while in a molten state in a clay pot oven.
Cylinder glass was then collected from the pot and put into a molten globule and blown, being
continually manipulated in a furnace. Glass coloured in this way was known as pot muntil until
it formed a large cylindrical bottle shape. It was then cut open, laid flat and annealed to make
it stable. This is the type of glass most commonly used for ancient stained glass windows.
Metallic salts were the added to produce colours in the glass. Copper oxides were added to
produce green, cobalt for blue, and gold was added to produce red glass.
Table glass was produced by tipping the molten glass onto a metal table and rolling it. The
glass was heavily textured by the reaction of the glass with the cold metal. Glass of this
appearance is commercially produced and widely used today, under the name of cathedral
glass.
Flashed glass, red pot metal glass was often undesirably dark in colour and very expensive.
The technique to produce red glass was called flashing. In this procedure, a semi-molten
cylinder of colourless glass was dipped into a pot of red glass so that the red glass formed a
thin coating. The laminated glass was cut, flattened and heat annealed. There were a number
of advantages to this technique. It allowed a variety in the depth of red, ranging from very
dark and almost opaque, through ruby red to pale and sometimes streaky red that was often
used for thin border pieces. The other advantage was that the red of double-layered glass
could be engraved or abraded to show colourless glass underneath. In the late medieval
glass this method was often employed to add rich patterns to the robes of Saints. The other
advantage was that sheets could be flashed in which the depth of colour varied across the
sheet.
In Early Christian churches of the 4th and 5th centuries there are many remaining windows
which are filled with ornate patterns of thinly-sliced alabaster set into wooden frames, giving a
stained-glass like effect. Similar effects were achieved with greater elaboration using coloured
glass rather than stone. Later the stained glass windows incorporate narratives. This is seen
in the windows that were drawn from the Bible with the story of Christ, saints or patrons.
History is also duplicated in narrative designs as is Literature. More importantly stained glass
windows that duplicated the story of Christ were known as the poor mans Bible. Not
everyone was able to read, therefore, the windows told the story.
Stained glass, as an art form, reached its height in the middle Ages. As Gothic architecture
developed into a more ornate form, windows grew larger, affording greater illumination to the
interiors. The elaboration of form reached its height of complexity in the flamboyant style in
Europe and windows grew still larger with the development of the perpendicular style in
England. The glass designs became more daring. The circular form, or rose windows,
developed in France from relatively simple windows then ultimately to designs of enormous
complexity.
In the 1500s a range of glass stains were introduced, most of them coloured by ground glass
particles. This was a form of enamel. Painting on glass with these stains was initially used for
small heraldic designs and other details. By the 1600s a style of stained glass had evolved
that was no longer dependent upon the skilful cutting of coloured glass into sections. Scenes
were painted onto glass panels of square format, like tiles. The colours were annealed to the
glass and the pieces were assembled into metal frames.
Modern stained glass windows often use machine made glass, slab glass, which as its name
suggests is very thick and so-called cathedral glass which is sometimes heavily textured.
Stained glass, as an art and a craft, requires the artistic skill to conceive the design, and the
engineering skills necessary to assemble the decorative piece, traditionally a window. Today
the art and craft of stained glass has evolved into window panels, lamps, vases, sun catchers,
wind chimes, bird housed and stepping stones. The possibilities are endless.