Lampwork Beads


Lampworking is a process where rods of glass are introduced into a flame in order to melt the glass so that it can be shaped. lampworkers today use torches that burn either propane or natural gas for the fuel, with either air or pure oxygen as the oxidizer. Lampworking is also known as flameworking or torchworking.

To create beads, lampworkers melt narrow rods of glass around a mandrel. A mandrel is a thin thin length of stainless steel. The space occupied by the mandrel becomes the hole through the bead. Turning the mandrel and holding it in different positions allows gravity to help the bead take form. Tools are also used to push and pull the glass into shape.

A lampwork artist understands the glass and knows how much heat it takes for glass to flow. He can manipulate color, shape, and understands how to add dots both inside and on the surface of a bead and how to paint thin lines with thin rods of glass. Lampworking is a skill that takes a great deal of practice.

Lampworking can be done with many types of glass, but the most common is soda-lime glass, sometimes called "soft glass", or Moretti after an early Italian manufacturer.

Different colors of glass must be carefully selected for compatibility with each other, both chemically 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 even violently shattering the piece. Different major types of glass, e.g., borosilicate and Moretti, are not compatible with each other. Chemically, some colors can react with each other when melted together. This may cause desirable effects in coloration, metalic sheen, or result in an aesthetically pleasing "web effect". It also can cause undesirable effects such as unattractive discoloration, bubbling, or devitrification.

Glass shrinks as it cools. Bringing a bead out of the flame and leaving it in the open air allows the outside of the bead to cool rapidly, while the inside is still burning hot. The stress point between the cool, shrinking glass and the hot center begins to grow, often causing the bead to crack. The best way to cool beads is in a kiln, where temperatures can be closely regulated. This cooling process is called annealing.

Annealing, in glass terms, is heating a piece until its temperature reaches a stress-relief point, that is, a temperature at which the glass is still too hard to deform, but is soft enough for internal stresses to ease. The piece is then allowed to heat-soak until its temperature is even throughout; the time necessary for this varies depending on the type of glass and thickness of the thickest section. The piece is then slowly cooled at a predetermined rate until its temperature is below a critical point, at which it can no longer generate internal stresses, and then the temperature can safely be dropped to room temperature. This relieves the internal stresses, resulting in a piece which should last for many years. Glass which has not been annealed will usually at least crack, and can shatter due to a seemingly minor temperature change or other shock.


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