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Home Page --> Tutorial Lesson 2, Glassblowing Terminology

Tutorial Lesson 2, Glassblowing Terminology
Lesson 1
(Introduction and Safety)
Lesson 3
(The Glassblower's bench)

Glassblowing Terminology

Anneal - The process of removing stresses introduced into the glassware during the glassblowing process.

Annealing Oven - A piece of equipment used to remove the stress in glassware.

Annealing Point - The temperature at which the stress in glass is removed. Annealing point temperatures are different for each type of glass.

Blowhose Assembly - This tool is used to blow air through to shape the glass. The blowhose will have a mouthpiece at one end and a swivel at the other. The swivel is a device that allows the rotation of glass that will be blown. The swivel is connected to the glass by latex or rubber tubing or a stopper/tubing assembly. The blowhose is usually about six (6) feet long and 3/16" ID. Latex is commonly used because of its light weight and low cost.

Borosilicate Glass - This is the type of glass most commonly used in the laboratory. It is a heat-resistant glass which contains in the range of 5% boric oxide. In addition to outstanding resistance to heat and thermal shock, borosilicate glasses are known for chemical durability and low coefficients of thermal expansion. Trade names you may be more familiar with are PYREX (Corning), KIMAX (Kimble) and DURAN (Schott). In scientific glassblowing the glass used comes in tubing, rod or sheet form. It is usually four (4) foot lengths. The diameters are expressed in millimeters.

Burners - These devices are usually designed for stationary use at the bench or lathe. The glass being worked is moved into and around the flame. The flame size is determined by valves that adjust the flow and mix of fuel gas and oxygen.

Calipers - A tool used to measure the internal diameter and/or the outside diameter of glass tubing or rod, and wall thickness.

Corks - These are fixed size stoppers for temporarily sealing openings in the glass. They are typically made of natural cork or rubber.

Cutting Tool - An instrument used to scratch the surface of glass tubing or rod. See Tungsten Carbide Knife below.

Diamond Scribe - A hand held tool with a diamond point used to make a permanent mark on glass.

Didymium Eyeglasses - Didymium lens protect your eyes from certain visible and UV light produced in the glassblowing process. They enable the glassblower to see the glass while it is being worked in the flame.

File - Files may be used to scratch the glass tube or rod surface. Three-corner (trianglular) files are the easiest to use.

Fire Polishing - The process of using a flame to smooth the ends of glass tubing or rod.

Flint Lighter - A handheld tool used to create a spark when igniting a torch or burner.

Fused Silica - These are amorphous (non-cystalline) silica glasses in the Quartz family.

Glass Components - Are prefabricated items usually purchased from glassware suppliers. Examples include o-ring connectors, joints, and stopcocks.

Glass/Ceramic Tape, Tubing and Pads - These are asbestos substitutes that find use as spacers, supports, insulators, etc. while glassblowing.

Glassblowing Lathe - A piece of equipment used as an aid in glass rotation.

Glass Saw (Cut-Off Wheel) - An electric-powered tool used to cut glass tubing and apparatus.

Graphite/Carbon Rods and Shapers - Tools used to form or shape hot glass. These hand held tools may be found in rod, flat , taper and custom forms.

Hard Glass - This term is used by glassblowers to generically describe glass in the borosilicate family. Most scientific glassblowing involves hard glass. See "soft glass" below".

Hot Glass Rest - Any object used to hold or contain hot glass.

Hydrogen - This fuel gas mixed with oxygen to generate temperatures hot enough to work quartz. It is highly flammable; be sure to consult the MSDS before working with it.

ID - Inside Diameter.

Lapping Wheel - A piece of electrically-powered equipment used to create flat surfaces on glass.

Markers - Wax pencils or inks used in identifying specific points/information on glassware. Depending on the type of marker, the marks may or may not be permanent after heating.

Natural Gas - This fuel gas is mixed with oxygen to generate temperatures hot enough to work borosilicate glass. It is composed mainly of methane with trace amounts of nitrogen and ethane. It will not generate a flame hot enough to work quartz. It is highly flammable; be sure to consult the MSDS before working with it.

OD - Outside Diameter.

Oxygen - Pure oxygen gas is mixed with hydrogen, natural gas or propane when using a burner or torch. As an oxidizer, it enhances the combustion process, permitting hotter flames than if the fuel gas was used alone. Pure oxygen is an exceedingly reactive and dangerous. Be sure to consult the MSDS and/or your gas supplier before working with it.

Pluro Stopper - These are adjustable size rubber stoppers used in sealing openings in glass.

Polariscope - This instrument is used to detect strain/stress in glass that could lead to breakage if not removed through annealing.

Propane Like natural gas, propane is a fuel gas mixed with oxygen to generate temperature hot enough to work borosilicate glass.

Quartz - This family of glass is almost pure silica (SIO2). It is used extensively in the semi-conductor industry , for high temperature applications, and for spectroscopy at wavelengths where borosilicate glass might cause interference. A Fused Quartz Properties & Usage Guide is available at National Scientific Company.

Regulator - Gas regulators are single or double stage pressure control devices installed between glassblowing tools such as torches and the gas manifold, delivery line, or compressed gas cylinder supplying the gases to them. Air Products has a terrific SafetyGram on regulator selection, installation and operation.

Ring Stand and Clamp Assembly - A ring stand is a common laboratory stand used with an adjustable clamp to hold glassware stationary. The clamp fingers should be covered or protected from the direct flame of your torch. Soft flexible braided glass/ceramic tubing is available for this purpose.

Rotate - The process of continually turning glass tubing or rod when it is in the flame or in a softened state. Rotation ensure that all sides of the tube/rod are exposed to the flame and are at equal temperature.

Soft Glass - These glasses are in the soda-lime family and typically contain about 71-75% silica, 12-16% soda, 10-15% lime, and coloring agents. Soft glass is not generally used in scientific applications because of its low softening point and brittle nature. It is primarily in lampworking (neon signs) and artwork.

Softening Point - The temperature at which glass will sag under its own weight under certain conditions.

Strain or Stress -
This is tension or compression in glass developed during the heating and cooling stages of the glassblowing process. Stress/strain are relieved through annealing in a cool flame or, ideally, an annealing oven.

Thermal Shock - Sudden, rapid cooling or heating of glass surface that may produce cracks or fractures. Hard borosilicate glasses are more resistant to thermal shock than soft glasses.

Torch - Torches are usually handheld. Unlike stationary burners (glass is moved into the flame), the torch is moved around the glass, which is stationary.

Tungsten Carbide Knife - This hand tool is used to create a scratch on the glass wall surface to intiate a "cut" in the material.

Tungsten Pick - This handheld tool is used to "sew" small holes and cracks in glass together. A sharpened tungsten rod (1/16 to 1/8 inch OD) is attached to a handle, preferably one that does not transmit heat. This tool is usually 6 -10 inches in overall length.

Working Range - The temperature within which which glass is hot enough to shape, seal or bond.

Tutorial Lesson 2, Glassblowing Terminology
Lesson 1
(Introduction and Safety)
Lesson 3
(The Glassblower's bench)

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