History of plate glass manufacture

Thea Burns <burnsd [at] post__queensu__ca> writes

>Information on the history of plate glass manufacture is sought.
>Evidence to look for in attempting to assess the date of manufacture
>of plate glass sheets is also sought.

    1.  The casting of mirror plates was commenced in France by
        Abraham Thevart in about 1688, resulting in the founding of
        the St. Gobain glassworks, which was the principal producer
        of this material until the late 18th century, when it was
        introduced into England. Plates of unprecedented size were
        being produced by 1691.  The method comprised pouring glass
        onto a metal table, spreading it evenly with rollers,
        annealing, grinding, and polishing.

        Distortion of the image is often seen in early plate glass
        even when perfectly flat.  This is caused by an
        inhomogeneity in the composition of the glass due to
        imperfect mixing of the raw materials. The mechanical
        stirring of molten glass was not introduced until 1798 by
        Guinand, and was perfected in 1805. Chance took out a
        British patent for the process in 1838, but it was not
        routinely adopted for about another decade.

    2.  In 1884-87 Chance introduced the rolled plate process,
        whereby glass was poured onto an inclined metal plane and
        then passed between rollers, followed by grinding and
        polishing.

    3.  Continuous ribbon production was invented at the Ford Motor
        Company in 1920, and in 1926 continuous production was
        achieved by flowing glass from a tank furnace over a weir,
        and then onto rollers. This was put into production by
        Pilkington Bros., who developed the continuous grinding and
        polishing process in 1925. Continuous rolling, grinding and
        polishing of sheet glass was in operation by about 1930.
        From 1937, both sides of the glass were ground and polished
        simultaneously.

N.B.  If the query relates to glass used for framed works of art on
paper, the following types of glass may be found, although plate
glass is in fact rarely used for this purpose:

    1.  Cylinder or broad glass.

    2.  Crown glass.

    3.  Plate glass.

    4.  Drawn sheet glass.

    5.  Float glass.

With some practice, these five types of glass are readily
identified, but precise dating is not really feasible, although
various features can lead to a very general idea of age.

Dr. Nigel Seeley
The National Trust
36, Queen Anne's Gate
London, SW1H 9AS
+44 171 447 6521
Fax: +44 171 447 6540

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                  Conservation DistList Instance 10:58
                Distributed: Tuesday, December 17, 1996
                       Message Id: cdl-10-58-003
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