The principal network former in ordinary commercial glass is
Answer: A
Silica builds the continuous random network that gives glass its character, while soda and lime modify it. Alumina is a minor addition that improves durability rather than a former in its own right. The random network is what makes the solid a glass.
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Match each glass batch constituent with the role it plays.
List I
A. Silica sand
B. Soda ash
C. Limestone
D. Cullet
List II
1. the stabiliser that resists water attack
2. the network former
3. recycled glass that reduces melting energy
4. the flux that lowers the melting temperature
Answer: B
Correct answer: A-2, B-4, C-1, D-3
Four constituents with four distinct jobs. Silica sand is the network former, the glass itself. Soda ash is the flux, bringing the melting temperature down from around 1,700 degrees to something a furnace can sustain economically. Limestone is the stabiliser, supplying the lime that makes the glass durable. And cullet is recycled glass, which melts more readily than raw batch and so reduces the energy required.
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Soda ash is added to a glass batch in order to
Answer: C
Correct answer: lower the melting temperature usefully
Pure silica melts near 1,700 degrees, which is impractical for volume production. Sodium oxide from the soda ash disrupts the silica network and brings the melting temperature down by several hundred degrees. What it does not do is improve the glass - it makes it soluble, which is why lime must be added alongside it.
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Assertion (A): Lime is added to a soda silica glass rather than leaving soda as the only modifier.
Reason (R): Soda silica glass alone is attacked by water and would not survive in service.
Answer: D
Both are true and the reason gives the necessity: the historical name water glass belongs to exactly that soluble composition, and lime is what makes the glass durable enough for bottles and windows. Three components make up almost the whole batch.
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State whether the following is true or false.
A glass with soda but no lime would dissolve slowly in water.
Answer: A
Correct answer: True
Soda-silica glass without lime is water glass, and it genuinely dissolves - it is sold as a solution for exactly that reason. Lime is what makes the composition durable, by binding the network against attack. Soda lime glass is therefore a three-part compromise: silica for the structure, soda so it can be melted, and lime so the result survives contact with water.
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Cullet is added to a glass batch mainly because it
Answer: B
It has already been through the melting reactions, so it needs only to be brought to temperature. High cullet ratios are limited by colour mixing and by contamination in the recycled stream. Green and clear cullet cannot be mixed freely.
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Fining of molten glass is the operation of
Answer: C
Sulphate or another fining agent releases gas that sweeps the small bubbles out as it rises. Seeds and blisters left in the glass are among the commonest defects in flat and container ware. The bubbles come from the melting reactions themselves.
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Arrange the stages of glass manufacture in order.
1. fining and conditioning of the melt
2. batch mixing of sand, soda ash and limestone
3. forming and then annealing
4. melting in the furnace
Answer: D
Correct answer: 2 - 4 - 1 - 3
The order follows the material. The batch is weighed and mixed, melted in the furnace, then held while fining removes the bubbles and conditioning brings it to a uniform working temperature. Only then is it formed, and annealing follows immediately to remove the stresses that forming and cooling introduced.
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The float process forms flat glass by
Answer: A
Both surfaces come out flat and parallel with no grinding, which is what made the process transform the industry. Tin is used because it is dense, melts low and does not react with the glass. The ribbon is drawn off the far end of the bath.
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Assertion (A): The float bath is kept under a reducing atmosphere.
Reason (R): Tin oxide would form on the bath surface and mark the glass.
Answer: B
Both are true and the reason gives the purpose: a nitrogen hydrogen mixture keeps the tin metallic, since any oxide would be picked up by the ribbon and show as a defect on the surface. Hydrogen in the atmosphere keeps the tin reduced.
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