A BIT OF HISTORY4 4000 YEARS AGO the Egyptians and Persians mastered the art of fusing and slumping glass. The Egyptian chemists used these processes to create art forms for the pharaohs. The knowledge they gained, while working with this complex and unpredictable, material continues to inspire glass artists today. The age old technique of kiln-forming glass is a fascinating and magical transformation of glass when combined with heat. Once the design has been completed the piece is stacked in a kiln. The kiln is heated to approximately 1500 degrees. The temperature varies greatly depending on many variables including the type of process, the type of glass and the thickness and size of the entire piece that is being fused. When the process temperature is reached, the glass is baked or soaked. This soaking process causes the glass to attain a liquid state. As a result the layers either bend to a mold or fuse and become one solid piece. Additional treatments to the surface of the glass may be added and once again the heating process is repeated. The process, temperature, and soak time are dictated by the specific applications to the glass. During each process the glass must be slowly cooled to room temperature. An annealing process is used which ensures that the finished piece of glass will be free of any stress which could crack or shatter the glass. The annealing process, depending on the size and thickness of the project can take from several hours to several days. COLORS OF GLASS
Adding different metal oxides to sand, soda and lime, the basic formula for glass creates different colors. For example: greens and aqua glasses usually have iron, while amber and brown colors are produced by adding small amounts of iron and sulfur. Light blues require copper, while dark blues require very small quantities of cobalt. Amethyst glass contains manganese. Opaque white can contain either tin or calcium. Selenium is one metal oxide that is used to produce reddish colors. Some reds and pinks even have a bit of gold in them! The brilliantly colored dichroic glass is created through the application of a variety of metal oxides such as titanium, magnesium and silicon in a high temperature vacuum furnace to either clear or black glass. The finished product has more than one color, and the different colors can be seen when the glass is viewed from different angles. Technically, there are three colors in the finished piece: transmitted (when light passes through the clear glass), reflected (light bounces off the glass and reflects a second color) with the third color viewed by looking at the glass from a 45 degree angle. If the base glass is black, however, there is no transmitted color to be seen. In order to be fusible, the base glass must be tested compatible. Due to the layers of metal oxides, this glass is stiffer than other fusible glass and so requires special handling. In addition to adding to the beauty of finished work and it also adds to the cost. BULLSEYE GLASS LEAD FREE The glass I use is specially designed to be fused in a kiln. The larger the piece is, the longer the time required for this process. In general, it takes about 24 hours before the fused piece is ready to be removed from my kiln. Fusible glass is also "tested compatible" which means that each sheet of this handrolled glass will fuse properly with any other sheet that has the same rating and Coefficient of Expansion (COE). The COE means that the glass heats and cools at the same predictable rate. Without this feature, different pieces of glass could not be fused together, they would shatter. This is part of what makes fused glass different (and therefore more costly) than stained glass. FUSED GLASS As the name suggests, fused glass is the process of taking sheets of glass and attaching them or "fusing" them together. Heat from a kiln adheres the glass pieces together. The more heat, the closer together the class becomes. At lower temperatures, the heat can make the glass pieces stick together. However, each piece can still be felt and thus a 3-D effect is created. At higher temperatures, up to 1800 degrees, the glass pieces become completely fused into each other so that when you run your hand across it, you do not feel each piece of glass any more. It has become one, smooth piece of glass. Basically, how are fused pieces created? In a nutshell, the process of fused glass requires sheets of glass to first be cut into the desired shape or shapes. Then, the pieces of glass are assembled, and a little glue is used to temporarily allow the pieces to stick together. Next, the assembled glass design is put into a kiln. As the kiln heats up, the glass contracts, expands, and adheres together. Occasionally, the kiln is checked until the piece is melted to the artist''s satisfaction (for example, 3-D or smooth). Next, the item is annealed. If the glass were to be taken out of the kiln while still hot, it would crack. So, the kiln temperature is slowly lowered to allow the glass to slowly cool down. Once the glass has properly cooled down, the fusing process is finished. Other steps can follow this depending on the artist''s needs. For example, if the piece isn''t fused to his liking, it can be fired in the kiln again. SLUMPING AND FUSING If the glass is to be slumped either into or on top of a form, the fused glass is placed on the mold and once again heated to a lower temperature than a fuse or tac. It remains at the process temp until the glass has softened and assigned the shape of the mold. All kinds of items can be made with fused glass. Items for the home such as plates, clocks, bowls, chimes, and wall hangings are some of today''s most popular fused glass pieces. As for jewelry, fused glass is most often used to create cabochons and pendants. I truely hope that you enjoy gazing at the wonders of my glass as much as I enjoy creating it. Sally |
