Glossary of Glass-Making Terms and Techniques

Sparkles From the Deep

Glossary of Glass-Making Terms and Techniques

BLOWING TECHNIQUE: A technique in which air is blown through a long pipe attached to a gob of molten glass, thus enabling the glass to be made into different shapes. There are two kinds of techniques, free-blowing and mold-blowing.
BOW-BASE: A kind of base made from thick glass threads shaped first into a bow, and then into a ring.
CAMEO: In this technique, layers of different colored glass are applied over a surface of a single color. Later, carving is used to create a contrasting effect.
CASTING: This technique involves the shaping of molten glass in a closed mold or over an open former. Open-ended vessels were cast over an open former; for closed vessels, the lost-wax technique are used.
COLLARED-RIM: A kind of rim in which the glass is folded out, down, and up.
CORE-FORMING: Also known as sand-casting. Sand, wrapped up in a cloth on the end of a rod, is plunged into molten glass in a crucible, or rolled in hot powdered glass, or where molten glass is rubbed on this core by a tool. The thickness and shape of the container is regulated by how many layers of molten glass is applied. The rim, handle(s) and base are added later in a final heating. Different colors of glass threads may also be draped around the container for ornamentation. In the final step, the stick is removed and the clay or sand inside the cloth is removed.
CUSHIONED-BASE: A kind of base which occurs by flaring of a piece of hot molten glass that joined to bottom.
CUTTING TECHNIQUES: With the help of minerals like corundum or diamond mounted on the end of a wheel-cutter, ornamentation can be made on cold glass. It is used in lathe-cutting, surface-cutting and burnishing. With the massive-cutting technique, larger glass pieces are given a rough shape. May also be used like a drill to facilitate the emptying out of the inside of the container.
DULLNESS: The loss of permeability and brightness of glass due to the effects of the environment.
FIRE POLISHING: Final introduction of glass vessels into furnace in order to smooth rough surfaces and burrs on the rim.
HOLLOWING: Indentations on the glass surface caused by air bubbles that rise to the surface during glass-making.
IMPURITIES: The remnants of sand, clay, earth or molten glass slag on the surface of containers.
INTERNAL CRACK: Cracks that occur during the annealing of the vessel.
INVERTED BASE: A kind of base-disk made by blowing a glass pellet into containers.
IRIDESCENCE: The appearance of a variety of color tones in different lights, an effect of the weathering process. First the area gets cloudy, then it flakes off in pieces. The vessel finally disintegrates into powder.
KICK: A depression in the bottom of a vessel, made with a pontil or a tool.
LOST-WAX TECHNIQUE: First, the wax is shaped over an open former and a closed mold is placed over it; then the wax is melted by heating and poured out through a hole. Powdered glass is then poured in, and with the final heating, it melts and takes the shape of mold.
MARVERING: A method of smoothing a surface by rolling the vessels on a flat surface.
MOLD-BLOWING: In this technique, vessels are shaped by blowing a molten glass gob, gathered on to the end of a long blowpipe, into a pre-made mold.
MOLD-PRESSING: For this technique both an open former and a closed mold are used. Powdered glass is heated for a long time in a closed mold. After it melts, the open former is pressed into this molten glass and squeezed. The glass is pressed between the open former and the closed mold.
MOSAIC GLASS TECHNIQUE: Different colored pieces of glass are placed side-by-side in a closed mold and heated until they fuse together. This technique has variations, such as gold-banded, millefiori and retichelli (netted container).
ORNAMENTATION: Decoration of glass surfaces, using colored and clear glass threads which can be draped, trailed, spattered, or sprinkled. Also includes decorations done using the wheel-cutter, lathe-cutter, twisting, grinding, etching and painting.
PONTIL: A metal rod that enables one to hold the unfinished glass piece from the bottom. While being held by the pontil, the rim, handle(s) and decorative elements are added. Pontil marks can sometimes be seen on the bottoms of some containers, but usually the mark is removed by shaving.
TOOLING: The use of tools (pliers, clamps, forceps) to shape a vessel. Sometimes traces of tool marks can be seen on the neck of the vessels, indicating that they have been shaped this way.
TRAILING: A decorative technique made by winding thin glass threads across the glass. Thin threads are known as snake threads; thicker threads, as ribbons.
TUBULAR-SHAPED BASE-DISC: A kind of vessel base that is indented from the bottom; has a tubular shape.
WEATHERING: The deterioration of glass objects due to adverse effects of the environment. Causes surface pitting and color changes. Caused by certain soil types, temperature changes, and humidity.