Making Glass

Product Specific Qualities Method of Manufacture Typical Formula
Glass Containers Bottles & Jars Relatively cheap when mass produced.
Resistant to mechanical shock, capable of being filled at very fast rates.
Some bottling plants fill in excess of 1000 bottles per minute.
Can be re-used and recycled.
Can be sterilised at high temperatures.
inert, do not impart taste or toxic substances.		 Automatically blown at high speeds.
Soda-lime silica
Approximate composition:
%
SiO2 74
Na2O 14
CaO 11
Al2O3 1
Flat Glass
  1. Relatively cheap.
  2. Can be toughened.
  3. Weather resistant.
  4. Can be coated.
Float process. Cast and rolled.
Soda-lime silica
Approximate composition:
%
SiO2 71
Na2O 16
CaO 9
Al2O3 1
MgO 3
Domestic Glassware for everyday use in home and catering
  1. Pleasant appearance.
  2. Ability to stand up to constant use.
  3. Does not affect contents
Mouth blown, pressed or fully automatic mass produced. Soda-lime silica
Approximate composition:
% %
SiO2 74 Al2O3 3
Na2O 16 K2O 1
CaO 5 B2O3 1
MgO 3
Radiation Shielding High density to absorb radiation. Extrusion and casting can be ground and polished to optical precision.
Soda-lime silica
Approximate composition:
%
SiO2 3
PbO 1
K2O 1
Thermometer Tubing Thermal stability over a wide temperature range, retaining transparency. Automatic or hand drawing. Soda-lime silica

Borosilicate

Lead glass

Depending on temperature

range required
Laboratory Glassware High chemical durability.

Low thermal expansion.

 Lampworking (made from tubing by heating and skilful manipulation).

Mouth and automatic blowing.

Sintering.

 Mainly Borosilicate or fused silica for extra low expansion coefficient
Full Lead Crystal Domestic Glassware
  1. Extra suitable for artistic hand shaping and mouth blowing.
  2. Brilliant finish, attractive when full or empty.
  3. Comparatively soft - easy to cut and polish or engrave.
Hand made by skilled craftsmen.
Lead glass
Approximate composition:
%
SiO2 3
PbO 1
K2O 1
Heat Resistant Oven to Table Ware
  1. Resistant to thermal shock.
  2. Attractive.
  3. Easy to clean.
  4. Can be used in microwave ovens.
Automatically pressed or blown. Borosilicate glass
Approximate composition:
% %
SiO2 80 Na2O 4.5
B2O3 12 Al2O3 5
Optical Glass
  1. Wide range of refractive indices.
  2. Wide range of dispersion coefficients.
  3. Perfect homogeneity.
  4. Complete transparency.
Extrusion and pressing, then ground and polishing. While range of compositions

Depends on application
Electrical Components: cathode-ray tubes, capacitors and resistors, computer components, printed circuits Good dielectric properties.

Low electrical losses over a wide range of temperatures.

High operating temperatures.

 Blowing.

Drawing - in rod form and in sheets.

Sintering and Pressing - glass is ground to fine grains and then is subsequently pressed into required shape and then fired.

 Wide range of compositions
Glass Building Blocks Resistant to normal temperature changes.

Resistant to atmospheric conditions.

Mechanical strength.

Attractive.

Translucent.

 Automatic pressing

- pressed in halves and then fused together

 Soda-lime silica glass

Similar to flat glass
Ballotini: minute glass spheres (1-60 microns) which reflect light High reflective properties: mixed with paint for road signs and cinema screens. flame drawing

- velocity of flames draws particles of glass up tower and as the softened glass falls on the outside, spheres are formed by surface tension effects.

 Soda-lime silica glass

Similar to flat glass
Glass Fibre High strength-to-weight ratio.

Resistant to attack by corrosive substances.

Resistant to high temperature.

Flame resistant.

High electrical resistance.

 Filament drawing.

Continuous filament.

White wool.

Crown process.

Can be woven into textiles or incorporated with plastics to form insulating materials, boat hulls, car bodies, etc.

 Soda lime silica and where resistance to weathering is necessary, a borosilicate glass is used, e.g.

Soda-lime silica glass

% %
SiO2 54.5 B2O3 8.3
Al2O3 14.5 Na2O 0.5
CaO 22.0
Lighting Glassware

1. Electric Light Bulbs

 Economical to produce.

Easy to manufacture by mass production methods.

Resistant to shock.

Impermeable and inert to gas, vapour and liquid.

Durable.

Transparent or translucent.

 Ribbon Machine

- produces bulb at the rate of over 1,000 per minute.

Blanks used in the manufacture of vacuum flasks are also produced by this machine
Soda lime silica glass
%
SiO2 72.5
Al2O3 1.3
CaO 6.5
MgO 3.0
Na2O 15.9
K2O 0.3
2. Special Glasses

(a) High pressure mercury vapour lamps

 Low electrical conductivity.

Resistance to intense chemical activity of mercury vapour.

 Special glasses can be formed by using manufacturing Wide range of compositions
(b) Aircraft fire-warning sensors Low melting point. processes, or, in some cases, laminated onto ordinary glasses  
(c) Glass for encapsulating electric components High electricity conductivity. i.e. sodium discharge lamps.  
3. Tubing for fluorescent lighting Low electrical conductivity.

Resistance to intense chemical activity.

Electrical discharge generates UV light which then causes fluorescent powder to emit visible light.

High efficiency.

Long life: 3,000 - 5,000 hours, i.e. about one year of continuous use.

 Automatic Drawing
Soda lime silica glass
%
SiO2 72.5
Al2O3 2.6
CaO 5.7
MgO 2.9
Na2O 14.6
K2O 1.2
B2O3 0.3
4. Domestic and industrial shades and bulkhead lights: inc. lenses for traffic lights, car lights and railway signal lights Resistant to high temperature.

Resistant to thermal shock.

Resistant to weathering. Accurate and non fading colour: subject to strict BS specifications.

 Mouth blowing.

Hand and automatic pressing - depending on quantities required.
  1. Soda-lime silica glass
  2. Laminated with opal glass
  3. Borosilicate glasses and opal glasses