The process is called Lampworking, flameworking or torchworking
but we'll refer to it as 'Lampworking' below.
Lampworking is a
type of glasswork where a torch or lamp is primarily used to melt the glass. Once in a
molten state, the glass is formed by blowing and shaping with tools and hand movements.
Although lack of a precise definition for lampworking makes it difficult to determine when
this technique was first developed, the earliest verifiable lampworked glass is probably a
collection of beads thought to date to the fifth century BC. Lampworking became widely
practiced in Italy in the 14th century. In the mid 19th century lampwork technique was
extended to the production of paperweights and became a popular art form, still collected
today. Lampworking differs from glassblowing in that glassblowing uses a furnace and glory
hole as the primary heat source, although torches are also used.
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 propane or LPG, or in some countries, butane for the fuel gas, mixed with either
air or pure oxygen as the oxidiser.
Lampworking is used to create artwork, including figurines,
trinkets, curios, Christmas tree ornaments, beads and much more. It is also used to create
scientific instruments as well as glass models of animal and botanical subjects.
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."
Soft glass melts at lower temperatures, however it does not react well to temperature
changes like borosilicate glass does. Because soft glass expands a lot more than hard
glass when heated, and contracts more when cooled, along with its brittle nature, during
cooling or even while working it, soft glass is more prone to cracking due to thermal
shock than borosilicate. If a piece cools too quickly in one spot, such as if cold water
touches a thin piece of soft glass, that part would solidify immediately, and cause a
crack. However, hard glass or borosilicate, would be more resilient. Borosilicate is just
like regular glass, but it has a more flexible molecular structure from being doped with
The colours of the glass must be 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. 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 coloration, metallic sheen, or result in an
aesthetically pleasing "web effect". It also can cause undesirable effects such
as unattractive discoloration, bubbling, or devitrification.
Borosilicate glass is considered more forgiving to work with, as its lower COE makes it
less apt to crack during flameworking than soda-lime glass. However, it has a narrower
working temperature range than soda-lime glass, has fewer available colours, and is
considerably more expensive. Also, its working range is at higher temperatures than
soda-lime glass, requiring larger 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
either to produce the desired final colour or to discolour if extra oxygen is present.
Further extensive history and an on-line glass museum is
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