This set of Food Packaging Technology MCQs focuses on “Manufacture of Glass – 2”.
1. Lehr is a deadplate.
a) True
b) False
View Answer
Explanation: The given statement is false. The containers, from the molder, are transferred from the deadplate to a large oven, known as a lehr, which is equipped with a belt conveyer.
2. The temperature during annealing is around ______
a) 250°C
b) 340°C
c) 540°C
d) 640°C
View Answer
Explanation: This is achieved by raising the temperature of the container to approximately 540°C, holding it there for a few minutes and then cooling at a rate which is consistent with the removal of stress from a predetermined wall thickness.
3. The temperature at which annealing is done is known as _________
a) melting point
b) softening point
c) transition point
d) gradient point
View Answer
Explanation: The temperature at which annealing is done is known as softening point of glass. It melts and reforms glass so that any cracks or deformity can be healed or removed.
4. The primary purpose of annealing is to improve transparency of glass.
a) True
b) False
View Answer
Explanation: The given statement is false. The function of the annealing lehr is to produce a stable product by removing any residual stresses resulting from non-uniform cooling rates during forming and handling.
5. During cooling, the outside surface is hotter than the inside.
a) True
b) False
View Answer
Explanation: The given statement is false. During cooling, the inside surface is hotter than the outside; this results in compression on the outer surface but tension at the inner surface. Sudden cooling results tensile stresses into the outer surfaces and compressional stresses in the interior surfaces. Poor annealing may result in breaking or cracking if interior is bruised or tension is high.
6. Lightweight bottles can handle temperature fluctuation better than regular bottles.
a) True
b) False
View Answer
Explanation: The given statement is true. Due to the better thickness distribution of lightweight glass bottles, they withstand a maximum temperature difference (progressive thermal shock) of 5°C–10°C higher than the regular weight bottles.
7. Narrow-neck glass containers are formed by _______ process.
a) blow and press
b) press and press
c) press and blow
d) blow and blow
View Answer
Explanation: Narrow-neck glass containers (bottles) are formed by blow and blow process. Bottles are made by a two step Blow & Blow process, in which a gob of glass is sent to a cast iron mold. The cast iron mold is externally air cooled and hence changes gob to a perform (also known as a parison or body blank).
8. Wide-mouth glass containers are formed by _______ process.
a) blow and press
b) press and blow
c) blow and blow
d) press and press
View Answer
Explanation: Wide-mouth glass containers (jars) are formed by press and blow process. In the case of jars, a two-step WMP&B process is used. The body blank or parison is formed by pressing the gob of molten glass against the mold walls with a large plunger. When the cavity is filled, glass is then pushed down into the neck ring and the finish is formed.
9. Formation of glass jars takes place through blow moulding.
a) True
b) False
View Answer
Explanation: The given statement is true. When the finish molding is complete, the plunger is retracted and air blown in from the bottom of the mold, enlarging the size of the bubble until the glass is pressed out against the blank mold to form a hollow, thick-walled preform or parison. The parison is then inverted and transferred to the blow mold. It elongates there as a result of its own weight and touches the base of the mold.
10. In the blow and blow process for glass container manufacture, the neck formation takes place before blank is blown.
a) True
b) False
View Answer
Explanation: The given statement is true. The blow and blow process takes place in the following steps-
i. Gob dropped into blank mold
ii. Neck formed
iii. Blank blown
iv. Blank transferred to blow mold
v. Final shape blown
vi. Finished bottle.
11. Wide mouth press and blow process for glass container manufacture does not include which of the following steps?
a) Blank press
b) Neck formation
c) Final shape blown
d) Plunging
View Answer
Explanation: Wide mouth “press and blow” process for glass container manufacture takes place in the following steps-
i. Gob dropped into blank mold
ii. Plunger presses blank shape
iii. Blank pressed Blank transferred to blow mold
iv. Final shape blown
v. Finished jar– give bullet points.
12. Impact strength of lightweight bottles is more than regular bottles.
a) True
b) False
View Answer
Explanation: The given statement is true. The impact strength of lightweight bottles is more than regular bottles. It is because, lightweight glass bottles have a more homogenous thickness distribution. It also has a superior vertical load strength and better impact strength, especially in the heel.
13. In narrow neck press and blow (NNP&B) process, the plunger and gob together have the same volume as the blank mold cavity.
a) True
b) False
View Answer
Explanation: The given statement is true. In narrow neck press and blow process, the plunger and gob together have the same volume as the blank mold cavity. In this, the gob is delivered into the blank mold. It is then pressed by a metal plunger to give it a shape.
14. What enables the glassmaker to decide exactly how the glass is distributed in the parison?
a) Density of gob and plunger
b) Mass of gob and plunger
c) Volume of gob and plunger
d) Temperature of gob and plunger
View Answer
Explanation: The volume of gob and plunger enables the glassmaker to decide exactly how the glass is distributed in the parison and, hence, to be able to more accurately control the uniformity of glass distribution in the finished container. Indeed, weight savings of up to 30% can be made. The second stage is similar to the B&B process.
15. What accounts for greater impact strength of lightweight bottles?
a) Uniform distribution of weight
b) Uniform distribution of pressure
c) Uniform distribution of volume
d) Uniform distribution of density
View Answer
Explanation: The uniform distribution of weight accounts for greater impact strength of lightweight bottles. The parison is blown to a finished container having a more uniform wall thickness and, as a result, higher strength.
Sanfoundry Global Education & Learning Series – Food Packaging Technology.
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