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Glassblowing 101

Lampwork is a form of glassblowing where the glass is heated over a flame.  Originally from the Middle Ages, the term lampwork referred to oil lamps with a blowpipe directed into the flame to increase the heat generated.  Today, modern torches use propane or natural gas mixed with compressed air or pure oxygen to generate the intense heat required.  More often it is now being called Torchwork or Flamework.

The majority of glass in general use worldwide is known as Soda Lime Glass or Soft Glass and is composed of quartz sand (silica, silicon dioxide, SiO2) soda (sodium carbonate Na2CO3 or sodium oxide Na2O) quicklime (calcium oxide CaO) and other oxides added for clarity or coloring.  The glass used most commonly for beads is soft glass referring to the relatively "soft" flame that can be used to work it, and how fluid it gets.  The soda acts as a flux to lower the melting point of silica and was originally produced from the ashes of seaweed and certain salt water tolerant plants.  Lime is added to strengthen the glass.  In some areas potash (potassium carbonate K2CO3) was substituted for soda which is produced from wood ash.  Historically, glass produced in factories varied depending on the local materials available.

Borosilicate glass known as Hard glass is a chemical and heat resistant glass made under the brand names "Pyrex", "Kimax", and "Duran".  Boron oxide is added to the glass mix, reducing the COE to 33, and making it react far less to thermal changes.  This makes it usable in the kitchen oven.  Most glass figurines, ships, and sculptural pieces, are made of hard glass because of it's tolerance to some parts cooling, while other areas are being worked in a flame.  It is called hard glass because it does not flow or soften as readily as soft glass and requires a hotter or "hard" flame.

After glass has been worked with heat, it will have residual stress within from temperature differences.  Annealing is the process of heating the glass very slowly to a set temperature determined by the make and type of glass.  It is held at this heat for a soaking period during which the glass relaxes all stress but does not change shape or slump.  It is then cooled very slowly to room temperature.   

C.O.E. Stands for "coefficient of expansion" which is a measure of how much a material expands for each degree it is heated, expressed such as 104 x 10-7/0C for soft glass.  The whole number value is generally used by itself when comparing different types of glass, such as COE 104 for Moretti, and COE 90 for Bullseye and COE 33 for the borosilicate family.