|
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. It is also known as flameworking or torchworking, as the modern practice no longer uses oil-fueled lamps. 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.〔Lierke, Rosemary, "Early History of Lampwork - Some Facts, Findings, and Theories," Glastech.Ber.65, 1992: p. 342.〕 Lampworking 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. Lampworking differs from glassblowing in that glassblowing uses a furnace 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 natural gas, or in some countries butane, for the fuel gas, mixed with either air or pure oxygen as the oxidizer. Many hobbyists use MAPP gas in portable canisters for fuel and some use oxygen concentrators as a source of continuous oxygen. Lampworking is used to create artwork, including beads, figurines, marbles, small vessels, Christmas tree ornaments, and much more. It is also used to create scientific instruments as well as glass models of animal and botanical subjects. ==Glass selection== Lampworking can be done with many types of glass, but the most common are soda-lime glass and lead glass, both called "soft glass," and borosilicate glass, often called "hard glass." Leaded glass tubing was commonly used in the manufacture of neon signs, and many USA lampworkers used it in making blown work. Some colored glass tubing that was also used in the neon industry was used to make small colored blown work, and colored glass rod, of compatible lead and soda-lime glasses, was used to ornament both clear and colored tubing. The use of soft glass tubing has been fading due, somewhat, to environmental concerns and health risks, but mainly due to the adoption of borosilicate glass by most lampworkers, especially since colored glasses compatible with clear borosilicate were developed. Soft glass is sometimes useful because it melts at lower temperatures, however it does not react well to quick temperature changes like borosilicate glass does. Soft glass expands and contracts a lot more than hard glass when heated/cooled, and must be kept at an even temperature while working with it, especially if the piece being made has sections of varying thickness. If thin areas cool below the "stress point", shrinking can cause a crack. Hard glass, or borosilicate, shrinks much less, so is more forgiving. Borosilicate is just like regular silicate glass (SiO2), but it has a more flexible molecular structure from being doped with boron. Glasses to be fused together 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) (is also used for Coefficient of Thermal Expansion. ) Glasses with incompatible COE, mixed together, can create powerful stresses within a finished piece as it cools, cracking or violently shattering the piece. 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. 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 or lead glass. However, it has a narrower working temperature range than the soft glasses, has fewer available colors, and is considerably more expensive. Also, its working range is at higher temperatures than the soft glasses, requiring the use of oxygen/gas flames instead of air/gas. 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 coloring chemicals in borosilicate glass react with any remaining oxygen in the flame either to produce the desired final color or to discolor if extra oxygen is present. Lead glass has the broadest working range of the three glasses, and holds its heat better when it is out of the flame. This gives one more time to adjust one's work when blowing hollow forms. It is also less likely to crack while working with it in making pieces of variable thickness than is soda-lime glass. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lampworking」の詳細全文を読む スポンサード リンク
|