Round-Bottom and Florence Flasks Blown from Glass Tube

A round-bottom flask is a glass sphere on a tubular neck: the round shape heats evenly and stands up to vacuum, so it is the flask for boiling and distilling. Blow it from the end of a borosilicate tube; flatten the bottom while soft and it becomes a Florence flask that stands on the bench. The picture: our diagram of the steps, from tube to round-bottom and Florence flask.