How Long Have People Been Recycling Glass in England?
Bishop's Wood glass furnace
NHLE entry: Listing details for Bishop's Wood glass furnace
The photograph above peers into the remains of the 16th-century glass-making furnace in Bishop's Wood, Eccleshall. The four round bases are clay crucibles that, when whole, would have been bucket-sized and held molten glass. The broken crucibles are still stuck to their platforms on either side of the fire trench where the wood fuel would have been burnt.
This scheduled furnace is a rare surviving example, allowing archaeologists and glass-making historians a privileged glimpse into the history of glass use and recycling in England.
The beginnings of glass use
Before the Roman conquest in AD 43 glass was a rarity in England, but afterwards people were able to obtain a wide range of glass cups, plates, bowls and bottles, and even glass window panes. Roman glass was made by heating white beach sand with natron, a salt mixture originating from dry lake beds in Egypt.
Incredibly most of the glass in use throughout the Roman empire at this time was produced in big centres in the eastern Mediterranean and then transported around the world. Chunks of raw glass were obtained by local glassworkers, who remelted them and shaped them into useable objects. Most Roman glass had a pale blue-green transparency, but completely colourless glass was used for quality tableware.
How did glass recycling start?
Glass recycling was very important in Roman times. New glass had to travel such a long way to reach many parts of the Roman world that glassworkers were keen to reuse old glass, particularly for basic items like bottles. Piles of cullet - broken glass ready for remelting - were found during archaeological excavations and barrels containing cullet have been discovered in Roman ship wrecks. Scientific analyses have shown that Roman glass may have been sorted before remelting, to separate colourless glass from the blue-green, much like in present-day bottle banks.
When was glass made from scratch in England?
After the Romans departed England glass became hard to come by, but by the 12th century AD glass-making furnaces had been established in some heavily wooded areas. The trees were essential because a different technology was being employed to make glass, using the ashes of plants as well as sand. As a result, a lot of plant material was needed, partly as a raw material but also because the furnaces themselves burned vast amounts of wood as fuel. Again the glass-makers reused old glass: adding cullet to fresh raw materials sped up the process and conserved fuel.
Nevertheless the rate at which the glass furnaces consumed woodland greatly concerned the government. In the early 17th century, King James forbade glass-makers from using wood and so newly adapted furnaces had to be established in areas where coal was available.
Remains of glass furnaces in Britain today
The locations of numerous medieval and post-medieval woodland furnaces are known, but the structures have been largely destroyed and the remains buried. A 17th-century furnace survives at Shinrone in Ireland, however, which gives us an idea of how others might have looked. We do know that they were built from stone and brick to withstand the very high temperatures (about 1400°C) needed to melt plant-ash glass.
Although the furnaces themselves have left little trace, original windows made from greenish plant-ash glass can be found in many medieval and post-medieval buildings, and are still admired today.
We provide further information on glasswork history in the following publications (published under our former name of English Heritage):
Archaeological Evidence for GlassworkingPublished 26 October 2018
This document provides guidance on identifying, investigating and interpreting the archaeological remains of past glassworking.
Medieval and Early Post-Medieval GlassworksPublished 31 October 2018
Introductions to Heritage Assets. An introduction to medieval and early post-medieval glassworks.