Step 1: Understanding the Concept:
Metal cans used in food preservation (canning) are structurally classified as either three-piece or two-piece cans.
This classification is based on the number of separate metal pieces used to assemble the finished container.
Step 2: Detailed Explanation:
Let us compare the construction of these cans:
- Three-piece cans: These consist of three separate metal components: a cylindrical body and two circular ends (the bottom end and the top lid).
The body is formed by rolling a flat metal sheet into a cylinder and joining the vertical edge.
This side seam can be joined using different methods:
1. Soldered side seam (A): Joined using a lead-tin alloy solder (largely phased out for food safety).
2. Cemented side seam (B): Joined using thermoplastic organic adhesives.
3. Welded side seam (C): Joined by electrical resistance welding, which is the standard modern method for three-piece cans.
- Two-piece cans: These consist of only two separate components: a seamless body with an integrated bottom, and a top lid.
The body is formed from a single flat metal disc through mechanical drawing processes.
A Drawn and Redrawn (DRD) can (D) is a type of two-piece can produced by initially drawing a cup and then redrawing it to reduce its diameter and increase its height without thinning the walls.
Because the body and bottom end are made from a single piece of metal, there is no side seam or bottom seam.
Therefore, a drawn and redrawn can is a two-piece can, not a three-piece can.
Step 3: Final Answer:
A drawn and redrawn can is a two-piece can, making it the correct answer.