The glass has an elongated funnel bowl engraved with barley and hops and a mercury airtwist stem.
The airtwist stem was developed by English glass blowers in the early 18th Century.
Once a blob of molten glass was attached to the bowl, it was pierced by nails and as the stem was drawn out and twisted, the pattern was formed and could be varied by changing the number, size and shape of the nails.
When a flat nail was used, a twist of such luminescence was created that mercury was once thought to have been introduced to the thread.
These twists continue to be known as mercury airtwists.
