Also known as culture tube or sample tubes, test tubes are the common piece of laboratory glassware. Consisting of finger-like length of glass the test tubes are open at the top end and have the rounded U-shape. Also some test tubes with larger sizes are specifically designed for boiling the liquids and are known as boiling tubes. Like other glassware the test tubes are transparent and the colors of chemicals and other elements inside can be clearly visible from outside.
In scientific laboratories, the test tubes are used for holding, mixing or heating the small quantities of liquid or solid chemicals. Usually the test tubes are used in qualitative experiments and assays. The rounded U-shaped bottom and the straight sides of the test tunes reduce or minimize the mass loss of liquids or solid while pouring. Also pouring becomes easier due to its particular structure. Sometimes the test tubes are used to capture gases as in electrolysis demonstrations. In the biology laboratories, the test tubes are used for handling the living organisms like molds, bacteria, seedlings and plant cuttings etc. The test tubes with stoppers are used to store the chemicals and biological samples temporarily.
Like all other glassware, the test tubes need to have certain features. The test tubes need to be heated and therefore it is necessary that they are resistant towards thermal shocks. Again, the test tubes have to deal with chemicals more than any other scientific glassware in the laboratory and hence they need to be chemical resistant. Like many other glassware, the test tubes are usually made of borosilicate glass.