Question

Which one of the following manufacturing techniques is used for making window glass?

• A. Investment casting
• B. Patenting
• C. Spray forming
• D. Float-bath method

Hint:

Associate "window glass" or "flat glass" with the "float-bath" or "Pilkington" process, which involves floating molten glass on a bed of molten tin.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify the specific manufacturing process used to produce large, flat sheets of glass, such as those used for windows.
Step 2: Detailed Explanation:
Let's analyze the given options:

• Investment casting: This is a process for making complex, intricate metal parts. A wax pattern is created, coated with a ceramic shell (the investment), and then the wax is melted out. Molten metal is then poured into the shell. This is not used for flat glass sheets.
  
• Patenting: This is a specific heat treatment process applied to high-carbon steel wire to produce a fine-grained pearlite structure, which is ideal for drawing into high-strength wires (e.g., for springs or bridge cables). It is unrelated to glass manufacturing.
  
• Spray forming: This is a process for producing semi-finished metal products. A stream of molten metal is atomized by high-velocity gas jets and sprayed onto a substrate, building up a solid deposit. It is used for metals, not glass sheets.
  
• Float-bath method: Also known as the Pilkington process, this is the modern standard for manufacturing high-quality, flat sheet glass. In this method, molten glass is poured from a furnace onto a shallow bath of molten tin. The glass floats on the tin, spreading out to form a flat surface with a uniform thickness. The surface tension of the glass and the perfectly flat surface of the molten tin create a glass sheet with near-perfectly smooth surfaces. This is the method used for making window glass.
  

Step 3: Final Answer:
The float-bath method is the correct technique used for manufacturing window glass.