From at least the early 17th century to the latter part of the 18th century, drawn glass beads over about 4 mm in diameter were generally rounded in European glasshouses using a method called a speo by the Italians who apparently invented it. The little-known process involved mounting a number of tube segments on the tines of a multi-pronged iron implement which was then inserted in a furnace and turned until the tubes were rounded to the desired degree. Beads produced in this manner often exhibit distinctive characteristics and are easily identified in archaeological collections.