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Glass tubes or glass tubing are hollow pieces of borosilicate or flint glass used primarily as laboratory glassware. Glass tubing is commercially available in various thicknesses and lengths. Glass tubing is frequently attached to rubber stoppers.
In the past, scientists constructed their own laboratory apparatus prior to the ubiquity of interchangeable ground glass joints. Today, commercially available parts connected by ground glass joints are preferred; where specialized glassware are required, they are made to measure using commercially available glass tubes by specialist glassblowers. For example, a Schlenk line is made of two large glass tubes, connected by stopcocks and smaller glass tubes, which are further connected to plastic hoses.
Although modifying glass tubing is no longer an essential laboratory technique, many are still familiar with the basic methods. A glass cutter is used to break pieces of glass tubing into smaller pieces. Freshly cut edges are flame polished before use to remove the rough edge. Glass tubing can be bent by heating evenly over a Bunsen flame to red heat. Hose barbs can be added to tubing, giving a better grip and seal for attaching plastic or rubber tubing.