Childrens Illustrated Encyclopedia

Glass

Containers of clear

glass both protect

their contents and

display them. lenses

are specially shaped

pieces of glass that

bend and concentrate

light. But not all glass

is functional; some

glassware is simply

decorative.

stiCky Clay and dry sand are more familiar on the end

of a shovel than on the dinner table. yet these are the basic

ingredients in the manufacture of the plates we eat from,

and the jars and bottles in which we buy preserved food

and drinks. Glass and ceramic materials share some useful

qualities: they resist the flow of heat and electricity, and

they have a hard, nonreactive surface. But they are

different in other ways: light passes through glass but not

ceramics, and ceramics stay strong when they are heated.

in their most basic forms, glass and ceramic objects are

brittle, but special additives and manufacturing methods

make both materials much tougher. Glass and ceramics

are ancient materials. the Egyptians made decorative glass

beads more than 5,000 years ago, and pottery is even older.

237

GlassBlowinG

the breath of the glassblower

inflates soft glass on the end of

a tube into a bubble. skillful

shaping makes the bubble into

fine glassware as it cools.

Find out more

Heat

light

Plastics

science

HEat rEsistanCE

Ceramics can withstand very

high temperatures. Ceramic

tiles keep astronauts cool

even when their space shuttle

glows red from the intense

heat of re-entry.

Heating sand,

limestone, and

soda ash in a

furnace together

with recycled

glass produces

molten glass.

The molten glass is

poured onto a pool of

molten tin, which makes

the glass spread into a flat

sheet suitable for windows.

The glass sets and

hardens on the cooler tin.

A lump of hot, soft

glass is placed in

a bottle-shaped mold.

Blowing air into the

mold makes the

glass inflate into

a bubble, which

expands to form

the bottle.

stainEd Glass

strips of lead hold together the

many pieces of colored glass in the

stained glass windows that decorate

homes, churches, and temples.

CEramiCs

damp clay is easy

to mold into

pottery and tiles;

heat sets the

shape permanently.

Ceramics resist heat

and electricity, so

they are ideal for

insulating objects

that get hot, such

as spark plugs.

Ceramic tile

Glass bottle for

holding ink

Ornate

glassware

jug made

in the

1930s

EnamEl

Enamel is a glasslike

layer on metal and

other objects that

protects them from

damage and corrosion. Colored enamel

gives ornaments a beautiful appearance.

Making glass

Glass bottle for

holding medicines

Spark plug

for car

engine

Fiberglass

strengthening

plastic with fibers

of glass produces

a material called

fiberglass or glass-

reinforced plastic,

which is tough

enough to be used

for car bodies.

Magnifying

glass which

is a large

convex lens.

Pottery mug

Recycled

glass

The glass then

cools and

sets hard.

Sand Limestone Soda ash

Glass and ceramics

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