Lampwork

Lampworking is a type of glassblowing that uses a gas-fueled torch to melt rods and tubes of clear and coloured glass. Once in a molten state, heating then shaping with a variety of tools and hand movements form the glass. It is also known as flameworking or torchworking, as the modern practice no longer uses oil-fueled lamps. Although the art form has been practiced since ancient times, it became widely practiced in Murano, Italy in the 14th century. In the mid 19th century lampwork technique was extended to the production of paperweights, primarily in France, where it became a popular art form, still collected today.
Early lampworking was done in the flame of an oil lamp, with the artist blowing air into the flame through a pipe. Most artists today use torches that burn either LPG, propane, natural gas, or in some countries butane, for the fuel gas, with either air or pure oxygen (which can be produced by an oxygen concentrator or from prefilled cylinders) as the oxidizer.
In addition to beads and artwork, lampworking is used to create scientific equipment, particularly for chemistry.

Rod and sheet
Most lampworkers, when bead-making, use rods of glass 7-8mm in diameter, though pre-made stringers are available in 1-3mm sizes, or rods of 15mm or more. Sheet glass can be cut with tools into strips, though it is easier to manipulate if attached to a rod first. Glass is also available in particles of various sizes (frit or powder), which is typically used for surface decorations in lampworked beads. Many manufacturers who once only sold their glass in sheet or very thick rod now provide rods for lampworking use. Window glass is usually not used, as it is not formulated for lampworking and there is little variation of colour available.
Soda lime glass
One of the most popular types of glass for lampworking is soda-lime glass, and is available pre-coloured. Soda-lime glass is the traditional mix used in blown furnace glass, and lampworking glass rods were originally hand-drawn from the furnace and allowed to cool for use by lampworkers. Today soda-lime, or "soft" glass is manufactured globally, including Italy, Germany, Czech Republic, China, America, and New Zealand.
Lead
In addition to soda lime glass, lampworkers can use lead glass. Lead glasses are distinguished by their lower viscosity, heavier weight, and somewhat greater tolerance for COE mismatches.
Borosilicate
Bead makers can use borosilicate glass, a hard glass requiring greater heat. This is laboratory glass, such as Pyrex. At one time, soft (soda lime and lead) and hard (borosilicate) glasses had distinctly different looking palettes, but demand by soft-glass artists for the silver strike colours on the one hand, and the development of the bright, cadmium based colours in the borosilicate line on the other, has diminished the distinctions between them.

Lampworking can be done with many types of glass, but the most common are soda-lime glass, sometimes called "soft glass" - and borosilicate glass, often called "hard glass". Leaded glass tubing was commonly used in the manufacture of neon signs, although its use has been fading due to environmental concerns and health risks.
Different colours of glass must be carefully selected for compatibility with each other, both chemically (more of a concern with soft glass than borosilicate) and in terms of coefficient of thermal expansion (COE). Glass with incompatible COE mixed together, can create powerful stresses within a finished piece as it cools, cracking or violently shattering the piece. Different major types of glass, e.g., borosilicate and soda-lime glass are not compatible with each other. Chemically, some colours can react with each other when melted together. This may cause desirable effects in colouration, metallic sheen, or result in an aesthetically pleasing crazing effect. It also can cause undesirable effects such as unattractive discolouration, bubbling, or devitrification. The atmosphere of the flame has an effect on the glass surface, it can also cause discolouration, a metallic sheen, depending on whether the flame is oxidizing (more oxygen) or reducing (more fuel) and the type of glass used. Moving and shaping the glass whilst it is too cool can cause devitrification.
Borosilicate glass is considered more forgiving to work with, as its lower COE makes it less liable to crack during flameworking than soda-lime glass. In comparison to soda-lime glass, it has a narrower working temperature range, has in the past had fewer available colours (this situation has now changed somewhat, there are many businesses currently manufacturing coloured borosilicate glass), and is considerably more expensive. Also, its working range is at higher temperatures, requiring hotter torches and the use of oxygen instead of air. In addition to producing a hotter flame, the use of pure oxygen allows more control over the flame's oxidizing or reducing properties, which is necessary because some colouring chemicals in borosilicate glass react with any remaining oxygen in the flame to produce different surface colours, depending how much, or little oxygen is present.

Tools for lampworking are similar to those used in off-hand glassblowing. Graphite or steel pads, rods, and other shapes are used for marvering the glass. Brass, graphite, or wooden molds (usually of apple or cherry wood) can be used to mold the hot glass. Tungsten picks can be used to drag glass around on the surface, or to bore a hole through a piece. Steel jacks, usually coated with beeswax, are used to neck down or cut off a piece. The immense importance of graphite in glassblowing is due to its self-lubricating ability, and incredibly low density and thus its ability to absorb heat; this allows the graphite to touch the molten glass with minimal temperature contrast between the metal and glass. There is a wide array of glass blowing tools made of graphite for this reason.