Sheet Glass Manufacture The Float Process Reading Answers

Feb 23, 2023

Sheet Glass Manufacture The Float Process Reading Answers tests a candidate’s understanding skills through passages and questions. This IELTS reading topic Sheet Glass Manufacture The Float Process Reading Answers is an academic topic. Candidates will need to read the passage thoroughly to answer different types of questions. This IELTS reading passage has question types like: No more than 2 words, True/False/Not Given.

Sheet Glass Manufacture The Float Process Reading Answers has been taken from the book Cambridge IELTS 8. Student's Book with Answers. Candidates can follow IELTS Reading practice papers for more topics like Sheet Glass Manufacture The Float Process Reading Answers.

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Section 1

Read the Passage to Answer the Following Questions

Sheet Glass Manufacture The Float Process Reading Answers

Glass, which has been made since the time of the Mesopotamians and Egyptians, is little more than a mixture of sand, soda ash and lime. When heated to about 1500 degrees Celsius (°C) this becomes a molten mass that hardens when slowly cooled. The first successful method for making clear, flat glass involved spinning. This method was very effective as the glass had not touched any surfaces between being soft and becoming hard, so it stayed perfectly unblemished, with a 'fire finish'. However, the process took a long time and was labour intensive.

Nevertheless, demand for flat glass was very high and glassmakers across the world were looking for a method of making it continuously. The first continuous ribbon process involved squeezing molten glass through two hot rollers, similar to an old mangle. This allowed glass of virtually any thickness to be made non-stop, but the rollers would leave both sides of the glass marked, and these would then need to be ground and polished. This part of the process rubbed away around 20 per cent of the glass, and the machines were very expensive.

The float process for making flat glass was invented by Alistair Pilkington. This process allows the manufacture of clear, tinted and coated glass for buildings, and clear and tinted glass for vehicles. Pilkington had been experimenting with improving the melting process, and in 1952 he had the idea of using a bed of molten metal to form the flat glass, eliminating altogether the need for rollers within the float bath. The metal had to melt at a temperature less than the hardening point of glass (about 600°C), but could not boil at a temperature below the temperature of the molten glass (about 1500°C). The best metal for the job was tin.

The rest of the concept relied on gravity, which guaranteed that the surface of the molten metal was perfectly flat and horizontal. Consequently, when pouring molten glass onto the molten tin, the underside of the glass would also be perfectly flat. If the glass were kept hot enough, it would flow over the molten tin until the top surface was also flat, horizontal and perfectly parallel to the bottom surface. Once the glass cooled to 604°C or less it was too hard to mark and could be transported out of the cooling zone by rollers. The glass settled to a thickness of six millimetres because of surface tension interactions between the glass and the tin. By fortunate coincidence, 60 per cent of the flat glass market at that time was for six-millimetre glass.

Pilkington built a pilot plant in 1953 and by 1955 he had convinced his company to build a full-scale plant. However, it took 14 months of non-stop production, costing the company £100,000 a month, before the plant produced any usable glass. Furthermore, once they succeeded in making marketable flat glass, the machine was turned off for a service to prepare it for years of continuous production. When it started up again it took another four months to get the process right again. They finally succeeded in 1959 and there are now float plants all over the world, with each able to produce around 1000 tons of glass every day, non-stop for around 15 years.

Float plants today make glass of near optical quality. Several processes - melting, refining, homogenising - take place simultaneously in the 2000 tonnes of molten glass in the furnace. They occur in separate zones in a complex glass flow driven by high temperatures. It adds up to a continuous melting process, lasting as long as 50 hours, that delivers glass smoothly and continuously to the float bath, and from there to a coating zone and finally a heat treatment zone, where stresses formed during cooling are relieved.

The principle of float glass is unchanged since the 1950s. However, the product has changed dramatically, from a single thickness of 6.8 mm to a range from sub-millimetre to 25 mm, from a ribbon frequently marred by inclusions and bubbles to almost optical perfection. To ensure the highest quality, inspection takes place at every stage. Occasionally, a bubble is not removed during refining, a sand grain refuses to melt, a tremor in the tin puts ripples into the glass ribbon. Automated on-line inspection does two things. Firstly, it reveals process faults upstream that can be corrected. Inspection technology allows more than 100 million measurements a second to be made across the ribbon, locating flaws the unaided eye would be unable to see. Secondly, it enables computers downstream to steer cutters around flaws.

Float glass is sold by the square metre, and at the final stage computers translate customer requirements into patterns of cuts designed to minimise waste.

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Section 2

Solution with Explanations

Questions 1-8
Complete the table and diagram below.
Choose NO MORE THAN TWO WORDS from the passage for each answer.
Write your answers in boxes 1-8 on your answer sheet.

Early methods of producing flat glass

Question- 1

Answer- Spinning
Supporting Statement- “The first successful method for making clear, flat glass involved spinning”
Keywords- spinning
Location of Keywords- Para 1, line 4
Explanation- The production of glasses dates back to ancient times, with the initial technique being spinning to create transparent and flat glass.

Question- 2

Answer- unblemished
Supporting Statement- “This method was very effective as the glass had not touched any surfaces between being soft and becoming hard, so it stayed perfectly unblemished, with a 'fire finish'.”
Keywords- unblemished
Location of Keywords- para 1, line 6
Explanation- During the spinning procedure, the glass undergoes no contact with any surface from its molten to solid state, ensuring its flawless appearance.

Question- 3

Answer- labor-intensive
Supporting Statement- “However, the process took a long time and was labor-intensive.”
Keywords- labor-intensive
Location of Keywords- para 1, last line
Explanation- The process of forming glass is known to be labor-intensive and time-consuming due to the numerous human activities involved.

Question- 4

Answer- thickness
Supporting Statement- “This allowed glass of virtually any thickness to be made non-stop, but the rollers would leave both sides of the glass marked, and these would then need to be ground and polished.”
Keywords- thickness
Location of Keywords- para 2, line 3
Explanation- The question above requests for a continuous production of glass with almost any thickness.

Question- 5

Answer- marked
Supporting Statement- “ This allowed glass of virtually any thickness to be made non-stop, but the rollers would leave both sides of the glass marked, and these would then need to be ground and polished.”
Keywords- marked
Location of Keywords- para 2, line 4
Explanation- The manufacturing process enables the creation of glass with varying thicknesses without interruption. Additionally, the rollers imprint on both sides of the glass.

Question- 6

Answer- molten glass
Supporting Statement- “Consequently, when pouring molten glass onto the molten tin, the underside of the glass would also be perfectly flat”
Keywords- molten glass
Location of Keywords- para 4, line 2
Explanation- The flat and horizontal surface of the molten metal, governed by the theory of gravity, is crucial in the creation of the glass sheet. As the molten glass is poured over the molten tin, its underside is expertly flattened.

Question- 7

Answer- molten tin/ metal
Supporting Statement- “The best metal for the job was tin.”
Keywords- tin
Location of Keywords- para 3, last line
Explanation- According to Pilkington, the ideal metal for producing flat glass through the use of molten material would be Tin, and he had devised a plan to implement this method.

Question- 8

Answer- rollers
Supporting Statement- “This allowed a glass of virtually any thickness to be made non-stop, but the rollers would leave both sides of the glass marked, and these would then need to be ground and polished. ”
Keywords- rollers
Location of Keywords- para 2, line 4
Explanation- To implement the continuous ribbon method, the molten glass needs to undergo squeezing between two heated rollers, which consequently leave markings on both sides of the glass. Following this, the glass is grounded and polished.

Questions 9-13
Do the following statements agree with the information given in Reading Passage 1?
In boxes 9-13 on your answer sheet, write

TRUE if the statement agrees with the information
FALSE if the statement contradicts the information
NOT GIVEN if there is no information on this

Question 9. The metal used in the float process had to have specific properties.

Answer- true
Supporting Statement- “The metal had to melt at a temperature less than the hardening point of glass (about 600°C), but could not boil at a temperature below the temperature of the molten glass (about 1500°C).”
Keywords- less than the hardening point of glass, below the temperature the molten glass
Location of Keywords- para 3, line 4
Explanation- To carry out the floating process, the metal must be melted at a temperature that is lower than the glass's hardening point, i.e., 600 degrees Celsius. However, it should not boil at a temperature that is lower than the molten glass's temperature, which is 1500 degrees Celsius.

Question. 10 Pilkington invested some of his own money in his float plant.

Answer- NOT GIVEN
Explanation: There is no such information provided in the paragraph.

Question. 11 Pilkington’s first full-scale plant was an instant commercial success.

Answer- False
Supporting Statement- “ it took 14 months of non-stop production, costing the company £100,000 a month before the plant produced any usable glass.”
Keywords- it took 14 months of non-stop production
Location of Keywords- para 5, line 2
Explanation-After continuous production and an expenditure of nearly £100,000 every month, Pilkington's factory achieved commercial success in just 14 months.

Question. 12 The process invented by Pilkington has now been improved.

Answer- True
Supporting Statement- “the product has changed dramatically, from a single thickness of 6.8 mm to a range from sub-millimeter to 25 mm, from a ribbon frequently marred by inclusions and bubbles to almost optical
perfection”
Keywords- the product has changed dramatically
Location of Keywords- Last para, line 1
Explanation- The Pilkington process experienced various modifications, ranging from altering the thickness from 6.8 mm to 25 mm, to refining the ribbon from having inclusions and bubbles to achieving near-optimal clarity.

Question. 13 Computers are better than humans at detecting faults in the glass.

Answer- True
Supporting Statement- “Inspection technology allows more than 100 million measurements a second to be made across the ribbon, locating flaws the unaided eye would be unable to see”
Keywords- locating flaws the unaided eye would be unable to see
Location of Keywords- Last Para, line- 6
Explanation- The ribbon can be examined by computers at a rate exceeding 100 million measurements per second to identify imperfections that are invisible to the naked eye.

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