FAQ about Lampworking

Why do they call it lampworking?

Lampworking is a type of glasswork that uses a propane fueled torch and oxygen to melt rods of clear and colored glass. Torch temperatures reach as high as 1400 degrees. Once the glass is in a molten state, the bead is formed by shaping with a variety of tools, hand movements and gravity. Lampworking 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 propane or 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) as the oxidizer.

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."

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 violently shattering the piece. Different major types of glass, e.g., borosilicate and soda-lime glass are not compatible with each other. Chemically, some colors 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.

Tools for lampworking are similar to those used in glassblowing. Graphite or steel pads, rods, and other shapes are used for marvering the glass. Tungsten picks can be used to drag glass around on the surface, or to bore a hole through a piece.

After designing a piece, a lampworker must carefully plan how to construct it. Once ready to begin, the lampworker slowly introduces the glass rod into the flame to prevent cracking from thermal shock. The glass is heated until molten, wound around a specially-coated steel mandrel, forming the base bead. It can then be embellished or decorated using a variety of techniques and materials. All parts of the workpiece must be kept at similar temperatures lest they shatter. Once finished the piece must be annealed in a kiln to prevent cracking.

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 uniform throughout. The time necessary for this depends 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't generate internal stresses, and then 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 may crack or shatter due to a seemingly minor temperature change or other shock.

The most popular glass for lampworking is soda-lime glass, and is available pre-colored. 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 and America.

How are these beads made?

• Preparing the mandrel - The beadmaker starts by dipping a mandrel, or wire (stainless steel welding wire, cut into lengths) into a clay based substance (bead release) and letting it dry.

• Heating rod and mandrel - The flameworker selects rods of glass to heat in the flame of the torch. When both glass and mandrel are sufficiently warm, the beadmaker starts rotating the mandrel while allowing the glass to wind upon it.

• Shaping the bead - Beads are shaped using a combination of heat, gravity and tools such as graphite paddles, mashers, tweezers, and picks. Presses to create shapes and indent patterns into the glass are also used.

• Decorating the bead - Beads can be decorated by melting stringers, or chips of glass on the surface, creating dots or lines. With a sharp pointed tool, feathers, hearts or other designs may be produced. Metal decorations of copper, fine silver, gold, palladium and platinum are applied as metal leaf, wire, mesh or fuming.

• Striking - If silver based colors are used (striking colors), the bead must be heated for a few moments in the torch flame or kiln to allow crystals to reform in the glass. This temperature is slightly above the stress relief point.

• Annealing - Once completed, beads should be heated to 940°-1050°F (depending on glass type), until the piece reaches its "stress relief point", held at that temp for a short time, then slowly cooled to avoid thermal shock.

• Cleaning - once the bead has cooled, it is removed from the mandral by soaking in warm water and a dremel or other high speed drill with a diamond bit is used to clean the bead release from the hole.

• Cold working - The cooled bead can be further decorated. Standard cold working techniques can be employed such as sandblasting, faceting and polishing. Etching the finished piece with acid leaves a matte finish.