Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

GTBL042-14 GTBL042-Callister-v2 August 29, 2007 8:59

592 • Chapter 14 / Synthesis, Fabrication, and Processing of Materials

Pressing operation

Gob

Parison

mold

Suspended

parison

Finishing

mold

Compressed air

Figure 14.18 The press-

and-blow technique for

producing a glass bottle.

(Adapted from C. J.

Phillips,Glass: The

Miracle Maker.

Reproduced by

permission of Pitman

Publishing Ltd.,

London.)

pressing in a mold. This piece is inserted into a finishing or blow mold and forced to

conform to the mold contours by the pressure created from a blast of air.

Drawing is used to form long glass pieces, such as sheet, rod, tubing, and fibers,

that have a constant cross section.

Up until the late 1950s, sheet glass (or plate) was produced by casting (or drawing)

the glass into a plate shape, grinding both faces to make them flat and parallel,

and finally, polishing the faces to make the sheet transparent—a procedure that

was relatively expensive. A more economical float process was patented in 1959 in

England. With this technique (represented schematically in Figure 14.19), the molten

Raw

Materials

Heating

Zone

Fire

Polishing

Zone

Heater

Combustion

Gases

Controlled

Atmosphere

Float Bath Furnace

Cooling

Zone

Annealing

Furnace (Lehr)

Cutting

Section

Melting Furnace

Molten Glass

Liquid Tin

Figure 14.19 Schematic diagram showing the float process for making sheet glass.

(Courtesy of Pilkington Group Limited.)