The making of sheet glass using the technique of mouth-blowing.

The Anglo-Saxon abbot, Saint Benedict Biscop, is credited with bringing glass-making to Sunderland, and Britain, back in the 7th Century AD. The windows of Bishopwearmouth Monastery were glazed by Biscop and his team of glaziers. This tradition continued into the 20th Century and Sunderland’s glass factories produced some of the finest glass in the world. The Hartley Wood mouth-blown sheet glass factory in Sunderland was operational from 1892 to 1992 and made glass for Tiffany and cathedrals all over the world. The National Glass Centre Sunderland was set up to celebrate this local history.

The last remaining company in the UK, English Antique Glass in Birmingham, have recently ceased production of sheet glass although they do still hold stock and have the skills in-house to restart production should there be a sufficient demand.

The molten glass is gathered on the end of the blowpipe and is coloured by rolling in intensely coloured globs of glass known as frit. When the glass is the right size and shape it is gradually blown and shaped, continuously re-heating it, into a long wide bulb. Once the right shape is achieved the hot glass is cut open at both ends so that it becomes an open cylinder or tube which then has to cool and anneal. The cylinder is then cut along its length and reheated, during which it is carefully flattened out to become a sheet of coloured glass.

Most window glass in the early nineteenth century was made using the cylinder method. Unlike modern float glass, each piece is unique, with air bubbles and slight variations in design.

Handmade glass comes in a range of variations including clear, coloured, seedy, crackle (alligator skin appearance), and opal (a slightly obscuring glass).

• Stained glass

• Market issues: Most glass is now manufactured using the float method, or mouth blown glass is imported from other countries such as Poland and Germany.
• Training issues: There are no training routes available.
• Technical issues: There are many technical challenges to the successful production of this material, not least the challenge of successfully annealing the glass so that it does not spontaneously shatter during or after cooling.  The carcinogenic nature of some of the minerals used to colour the glass so that it retains its colour undimmed for over a millennium is another issue, as is the cost of raw materials such as gold which has to be melted into the glass to produce the most vivid pinks.

• National Glass Centre, Sunderland

English Antique Glass still hold the equipment and the skills to resume sheet glass making. There is potential for sheet glass making to resume, should there be sufficient demand from stained glass craftspeople and the sector.