The Science Behind the Shape
Plastic jugs are made using blow molding, a process that shapes melted plastic by inflating it inside a mold.
During this process, engineers include the dent to:
- Absorb expansion: when milk warms and expands.
- Prevent vacuum collapse: when it cools and contracts.
- Add rigidity: using a curved “dome” shape that strengthens the wall.
Fun analogy: it’s like the dome of a cathedral — curved for maximum strength with minimal material.
