Sep
15
German and French Coloured Glass
September 15, 2009 |
German factories.
DM Ml FROM “THE LAST JUDGEMENT’, COMPOSITION IN
RED GI.ASS
Si. Mary’s Church, Fairford, Gloucester, England.
15th century
In mediaeval times, when the most glorious
work in glass in western Europe was
achieved in the wonderful stained glass
windows produced for the great cathedrals
of the time, coloured glass assumed a new-
importance. Red glass was still made with
copper, but manganese was used to make
a pale rose-red or pink glass. Towards the
17th century there was much experimen-
tation in the making of red glass. The
problem was to produce a ruby glass that
remained consistent in quality. Many
formulae for coloured, including red, glass
were given in Antonio Neri’s VArte
Velraria, the standard Italian book on
glass-making, published in 1612. His
information was largely based on his
experience in Antwerp glass-works
founded by the Venetians. This book was
translated into English with a commentary
by Christopher Merrett in 1662; was
published in Holland in 1669; translated
into German, forming the greater part of
Johann Kunckel’s Ars Vitraria Experi-
memalh in 1679, and translated into
French in 1752.
RUBY GLASS BEAKER MOUNTED ON SILVER-GILT FOOT
Potsdam, Germany, end of 17th century.
Ht. 120 mm (475 in.)
It was not until the end of the 17th century
that a clear ruby or pink glass could be
made consistently well. This was the
contribution of Johann Kunckel (f.1630-
1703), a celebrated chemist, who directed
the glass-works at Potsdam in Germany
from 1678. His famous book Ars Vitraria
Experimentalise or Vollkommene Glasma-
cherkunst (complete art of glass-making,
1679) was to appear in five successive
editions, and remains a fundamental work
on the subject of glass technology in
modern times. By 1689, the date of the
second edition, Kunckel had learnt to
correct the crisselling (clouding in the
glass due to the excess of alkali) in Potsdam
glass by including a considerable quantity
of chalk in the mix. He made his ruby glass
by the addition of gold chloride to the raw
materials, and found out exactly how to
strike the red colour by reheating. The
idea was not all his own, for he was actually
putting into practical application in glass-
making the discovery of the precipitation
of gold by tin made some years previously
by Andreas Cassius.
RUBY GLASS BEAKER WITH SILVER-GILT MOUNTS
Southern Germany, second half of 17th century
Ht. 215 mm (8-45 in.)
With the death in 1688 of his patron, the
Elector Friedrich Wilhelm, Kunckel’s
fortunes were reversed. His experimental
glass-house on the Pfaueninsel was burnt
down, and various intrigues against him
eventually caused him to leave the Pots-
dam factory. In 1693 he went to Sweden,
was shortly afterwards ennobled as Kunc-
kel von Lowenstern, and finally died in
1703. Although he remains most famous
for the discovery of making ruby glass with
gold chloride, it is a mistake to imagine
that this secret stayed solely in the hands
of the Potsdam factory, for specimens of
similar gold-ruby glass are now attributed
to the Southern German glass-houses at
Munich or Freising. Kunckel is known to
have made glass of other colours, amongst
them blue, green, and agate, and he often
experimented on opaque white glass (’Por-
cellein-Glas’), but few pieces of his manu-
facture have survived.