TECHNICAL INFORMATION
416
Glossary of Glass Fabricating Terms
TECHNICAL INFO.
expansion coefficient —is the average increase in length per unit length per °C change in temperature over the range of 0 to 300°C. Since the expansion coefficient is affected slightly by annealing, the values given are for annealed glass. filling point —the level up to which a glass bottle has the nominal capacity. fine annealing —annealing to an extremely low stress and uniform index of refraction. finish —(1) the part of a bottle for holding the cap or closure. (2) stage in melting process after glass appears free of seeds.
lehr, leer —a long, tunnel-shaped oven for annealing glass by continuous passage. lime glass —a glass containing a substantial proportion of lime, usually associated with soda and silica. liquidus temperature —the maximum temperature at which equilibrium exists between the molten glass and its primary crystalline phase.
melt —a specific quantity of glass made at one time.
melting temperature —the range of furnace temperatures within which melting takes place at a commercially desirable rate, and at which the resulting glass generally has a viscosity of 10 15 to 10 25 poises. For purposes of comparing glasses, it is assumed that the glass of melting temperature has a viscosity of 10 2 poises. moil —(1) the glass remaining on a punty or blowpipe after a gob has been cut off or after a piece of ware has been blown and severed. (2) the glass originally in contact with the blowing mechanism or head, which becomes cullet after the desired article is severed from it.
fire cracks —cracks in ware caused by local temperature shock.
fire-polish —to make glass smooth, rounded, or glossy by heating in a fire.
forming —the shaping of hot glass.
Fourcault process—a method of manufacturing flat glass using a “vertical draw” process.
mold —a form (usually metal) in which glass is shaped.
frosted surface —treated to scatter light or to simulate frost.
mold mark —mark or seam on glassware resulting from a mold joint.
gaffer —head workman, foreman, or blower of a glass hand shop.
obsidian —a highly siliceous natural glass.
gather, (n) —the mass of glass picked up by the hand shop worker on the punty or blowing iron.
out-of-round —the imperfection of nonroundness in glass articles.
gather, (v) —to get glass from a pot or tank on the pipe or punty.
Owens process —a bottle-making process in which the blank or parison mold is filled by suction. paddling the rough —shaping of a piece of glass in a furnace by means of paddles or tools preparatory to the pressing operation for making optical glass blanks. parison —tube-like piece of plastic which air is blown through during blow molding. paste mold —a mold lined with adherent carbon, used wet for blown ware.
glass —an inorganic product of fusion that has cooled to a rigid condition without crystallizing. Glass is typically hard and brittle, and has a conchoidal fracture. It may be colorless or colored, and transparent to opaque. Masses or bodies of glass may be made colored, translucent, or opaque by the presence of dissolved, amorphous, or crystalline material. When a specific kind of glass is indicated, such descriptive terms as flint glass, barium glass, and window glass should be used following the basic definition, but the qualifying term is to be used as understood by trade custom. Objects made of glass are loosely and popularly referred to as glass; such as glass for a tumbler, a barometer, a window, a magnifier, or a mirror.
peephole —a small opening in a furnace used for observation purposes.
pig —a rest for blowpipe or punty during the gathering operation.
glass-blowing —the shaping of hot glass by air pressure.
pot —a one-piece refractory container for molten glass. Open pot: a pot wherein the glass surface is not protected from the furnace atmosphere. Closed pot: a pot having a crown protecting the glass from the furnace atmosphere.
glory hole —an opening exposing the hot interior of a furnace used to reheat the ware in hand working. gob —(1) a portion of hot glass delivered by a feeder. (2) a portion of hot glass gathered on a punty or pipe. graduated glassware —glassware that is marked with one or more graduations for volumetric measuring purposes. hackle marks —fine ridges on the fracture surface of glass, parallel to the direction of propagation of the fracture. hard glass —(1) a glass of exceptionally high viscosity at elevated temperatures. (2) a glass of high softening point. (3) a glass difficult to melt. (4) a glass hard to scratch. hot end —those manufacturing operations concerned with hot glass, that is, melting, forming, annealing. lampworking —forming glass articles from tubing and cane by heating in a gas flame.
pot furnace —a furnace for melting glass in pots.
pressed glass —glassware formed by pressure between a mold and a plunger. pull —the quantity of glass delivered by a furnace in a given time, usually 24 hours. punty —(1) a gathering iron of solid cross-section. (2) a device to which ware is attached for holding during fire polishing or finishing. reboil —reappearance of bubbles in molten glass after it previously appeared plain.
Powered by FlippingBook