This photograph shows the bottom of an 18th Century black blown glass mallet bottle found in Bradiford Water by Amelie Smith of Pilton in the summer of 2016. The term 'black glass' refers to glass which is usually in shades of dark green and amber but appears black because it is so thick. The colour comes from the impurities in the glass, the primary cause of which is iron oxide. The inset shows an example of a typical mallet bottle.
The first glass bottles of the free blown variety were made in England between 1630 and 1650. Because these varied so much in capacity, the English government passed a law forbidding the sale of wine in bottles in 1636. The term "black glass" was not formally used until the mid 1700s. At that point, private issue bottles with embossed seals became popular with wealthy patrons, both as a status symbol and to avoid confusion during the filling process at the vineyard.
The process of free-blowing involves the blowing of short puffs of air into a molten portion of glass called a 'gather' at the end of a blowpipe. It was used extensively as a glass forming technique until the late 19th century and is still widely used today for artistic purposes.
Many thanks to Amelie Smith for bringing this to The Pilton Story and showing it to the Barnstaple Museum to identify it.