Step 1: Understanding the Question:
The question asks for the primary function of the "Danner process" in the glass industry.
Step 2: Detailed Explanation:
Process Mechanism: In the Danner process, a continuous stream of molten glass flows onto a rotating, inclined ceramic mandrel (the Danner mandrel).
Formation: As the mandrel rotates, the glass forms a coating. Air is blown through the center of the mandrel. As the glass is pulled off the end of the mandrel by a "drawing" machine, it forms a long, continuous tube.
Rods vs. Tubes: If the air supply is turned off, the hollow center collapses, and the process produces solid glass rods.
Importance: This was the first successful automatic method for the mass production of high-quality glass tubing used for fluorecent lights, vials, and laboratory glassware. It allows for extremely precise control of diameter and wall thickness.
Analyzing Other Options:
- Fibers (A): Uses bushing/centrifugation.
- Sheets (B): Uses the Float process or Fourcault process.
- Containers (D): Uses IS machines (Press and Blow).
Step 3: Final Answer:
The Danner process is used for the continuous drawing of glass rods and tubes. Thus, option (C) is correct.