Glass onion
Onion bottles, or glass onions, were a shape of bottle used during the 17th and 18th centuries. Onion bottles most commonly were used to hold wine, but were also used for other spirits. At the beginning of the 17th century wine bottles were small and thin glassed, making them difficult to store and ship. During the 1630s, privateer turned inventor Sir Kenelm Digby teamed up with James Howell, creating a method of making stronger glass with hotter furnaces. These early onion bottles, usually referred to as "shaft and globe" bottles, evolved into onion bottle shape by the 1670s . This shape gradually evolved to be stouter with a wide base and short neck, reaching its height at the end of the 17th century before becoming elongated during the onset of the 18th century. Onion bottles achieved their dark green or brown colors from iron oxide found within the sand used to make them. The color was further darkened by the coal used to heat the furnaces, leaving the bottles almost black. Collars were applied to the tops for corks to be tied down. When shipped, they would be laid on their sides to soak the cork and help prevent  oxidation of the wine inside. Spirits like brandy were also added to the wine to extend its life when shipping overseas.