How To Work With Glass Tubing in the Lab

Glass tubing is used to connect other pieces of lab equipment. It can be cut, bent and stretched for a variety of uses. Here is how to work glass tubing safely for a chemistry lab or other scientific laboratory.

Types of Glass Tubing

There are two main types of glass that are commonly found in glass tubing using in labs: flint glass and borosilicate glass.

Flint glass gets its name from the flint nodules found in English chalk deposits that were a source of high purity silica, which was used to produce a potash lead glass. Originally, flint glass was a leaded glass, containing anywhere from 4–60% lead oxide. Modern flint glass tends to contain a much lower percentage of lead. This is the most common type of glass worked in labs because it softens at low temperatures, such as those produced by an alcohol lamp or burner flame. It is easy to manipulate and inexpensive.

Borosilicate glass is a high-temperature glass made from a mixture of silica and boron oxide. Pyrex is a well-known example of borosilicate glass. This type of glass can't be worked with an alcohol flame; a gas flame or other hot flame is needed. Borosilicate glass costs more and typically isn't worth the extra effort for a home chemistry lab, but it is common in school and commercial labs because of its chemical inertness and resistance to thermal shock. Borosilicate glass has a very low coefficient of thermal expansion.

Selecting Glass To Use

There are other considerations besides the chemical composition of the glass tubing. You can buy tubing in various length, wall thickness, inside diameter and outside diameter. Usually, the outside diameter is the critical factor because it determines whether or not the glass tubing will fit in a stopper or other connector for your setup. The most common outside diameter (OD) is 5 mm, but it's a good idea to check your stoppers before buying, cutting or bending glass.