Test tube

A test tube, also known as a culture tube, is a piece of laboratory glassware composed of a finger-like length of glass tubing, open at the top, with a rounded U-shaped bottom. Often, the top features a flared lip. This is to aid pouring of a liquid from the test tube to a beaker. A distinction between test tube and culture tube is often made, calling a tube with a lip a test tube and one without a lip a culture tube.

Construction and uses
Test tubes are available in a multitude of lengths and widths to serve a varying number of needs. They are typically used by chemists to retain multiple discrete samples of materials, usually liquids, during chemical procedures and experiments, and are designed to allow easy heating of these samples. Often, test tubes are constructed of expansion-resistant glasses such as Pyrex, and can usually be held in a flame such as that produced by a bunsen burner. A boiling tube is, however, preferred when heating samples for any length of time. It is used to hold chemicals.

Test tubes made from plastics are formed using injection molding. Injection molding is a process in which plastic is heated and then injected, under pressure, into a test tube mold commonly made from metal.