Georgian glass and its impact on window design

Throughout Georgian Britain, the predominant type of glass used to glaze domestic windows was Crown glass.  This was manufactured by blowing, from a set-quantity of molten glass, a small globe of material and then spinning this, using a puntil or punty stick, into a large, thin, spherical disk, usually just over five feet in diameter. Two early representations of Crown manufacture are reproduced below.

Once manufactured, the thickness of the disk was greatest at the centre where the puntil stick was attached. The quantity of glass at this point and the imperfection caused as the puntil stick was broken off made the central section unsuitable for general use and it was usually either re-smelted or used in low-end applications such as the glazing of stable and works areas. The nick-name bull’s eye has come to be associated with this piece of glass and, today, fake bull’s eyes are fabricated for use in theme pubs, etc. A photograph taken through a bull's eye pane is reproduced below.

Out of the remaining portion of the Crown sheet the glazier acquired the glass he would place into the main windows of a property. The geometry of the Crown sheet meant that pane size options were restricted. The glazer could cut very long, narrow, panes by selecting the area nearest the centre of the disk (panes of this shape were often required for margin-light work), or a set of more standard rectangular panes, if he did not sacrifice this part of the Crown disk.

As the panes that could be obtained from a Crown disk were far smaller than the average sash used in a window, a number of panes of glass were fitted into each sash, these being ‘joined’ together with glazing bars. Typically, a window might have 6 panes in the upper sash and 6 in the lower, making a so called ‘6 over 6’. Today, we call such multi-pane windows Georgian pattern, after the historical period during which they were the predominant type used. A picture showing such windows is reproduced below.

Crown glass has a unique visual quality, derived from its method of production, which makes it relatively easy to identify. The spinning of the glass globe into a disk resulted in a series of concentric rings radiating out across the sheet from around the puntil stick - these rings being a little akin to those formed when a stone is thrown into a pond. Once the Crown sheet has been cut into individual panes the rings appear as radial imperfections, usually one or two per sheet, these distort the image seen through a pane. These distortions are a sure marker of crown fabrication and quite unlike the more regular imperfections seen in other types of hand made glass, where the whole surface of a sheet takes on a dimpled appearance and there’s a full pane optical distortion.

We have lost the skill required to make commercial grade Crown glass and surviving panes should be thought of as rare antiques that require careful preservation in-situ.

Two characteristics of Crown glass, in particular, have resulted in much being lost (both accidentally broken and purposefully replaced). The material is exceptionally brittle and pane thickness is usually very thin, being on average just 1.5 - 2mm. During the Georgian period it was quickly recognised that hailstones and small pieces of blown debris could cause great damage to the glass and many properties were equipped with external to protect Crown glazed windows.

19th century storm shuttering in the Brighton & Hove area can be designated as being one of three designs. Hinged shutters, of the type often associated with Mediterranean properties and still widely seen around the city, rolling shutters, as can still be seen on a number of Kemptown and Brunswick Town properties and counterweighted shutters. All three types are reproduced below.

This last type of shutter has all but disappeared from our area and examples are not immediately obvious, although a half-dozen properties do still retain at least some parts of the shutter fittings and many more display evidence of such shutters having once been fitted. To spot houses that once had counterweighted shutters look at surviving original sash boxes for evidence of forwards channels to the main pair designed to take the main sashes, as can be seen in the photograph below.

Storm shuttering, if built with louver design, could fulfil an additional function. If operated in conjunction with the internal screening provided by fittings such as Venetian blinds, sub-curtains, etc, they could be used to control the quantity of light entering a room, in order to reduce ultra violet bleaching to fragile upholstery, paper products, etc.

At The Regency Town House we have researched the story of the counterweighted shutter, confirmed we were originally fitted with these devices, designed and manufactured a copy set and installed these at our main front elevation windows, as is illustrated in the picture below.

 Given the details provided above, it is clear that deploying storm shutters quickly during inclement weather was vital. In the Bevan’s correspondence of 15 and 18 June 1834 we learn of an occasion when the family’s servants failed act fast enough and between 66 and 100 panes of glass were lost. This likely represents some 30% of the total number of panes in the property and this level of damage was clearly significant.

Just as these letters are being written, in 1834, Robert Lucas Chance introduced his ‘improved cylinder sheet’ to the UK glass market. The technique used to produce this material eventually led to far larger panes of glass that were of considerably greater strength. Once such a product was available, fashionable families had their Georgian pattern windows replaced with ‘panoramic’ single pane sashes and at this point there was no reason to retain the old storm shutter systems. In their place came externally housed fabric roller blinds designed entirely to control light levels in the room. Even though, today, such blinds are rare the fabric blind covers often still survive on buildings, as illustrated in the photograph below.

By the end of the 19th century relatively few houses in Brighton & Hove had the old syyle of window and storm shutter in place and those that did were to see these fittings decay rapidly and face replacement.

Written by Nick Tyson

Feb 2009