Why do most milk cartons come in square boxes, while Coke packaging is round?(1)

In fact, the image of milk and Coke packaging has long been a commonplace for us. Have you guys ever noticed why most milk comes in square boxes while soft drinks like Coke come in round bottles?

Why are the bottles containing Coke designed to be round?

First, easy to hold (analysis of use scenarios)

In terms of consumer demand, Coke is generally consumed instantly on the spot, and is bought when you see it available in supermarkets, convenience stores and vending machines. The round bottle feels good in your hand and is easy to carry, so you can take a bottle anytime, anywhere.

Second, the need to resist pressure (physical property analysis)

A carbonated drink like Coke, which has air pressure inside, will generate strong air pressure during transport (think of your usual shaking of a Coke bottle), while the pressure is equalised at all points on the spherical surface and the pressure at each point is converted into a tensile force on the surrounding material. The best shape for a pressure container is a sphere or a cylinder in order to even out the pressure and make the most efficient use of the packaging material. Even if we were to make the pressure vessel square, the pressure (stress) inside would hold the shape close to round. Unless the material used is made very strong and very thick, regardless of cost. Thus, round bottle packaging meets exactly the pressure resistance requirements of Coke, which is difficult to achieve with angular cartons.

Third, mass production (process technology analysis)

Firstly, carbonated beverage bottles, the vast majority of which are PET bottles, are also made by blow moulding. This is because the use of bottles for liquid products is the most scientific, material-efficient, easy-to-make and least damaging mode of encapsulation, a mode that has been followed for centuries. In terms of product design, the circle has the largest area for the same circumference. This means that when packaging the same volume of beverage, choosing a round bottle can maximise material cost savings; secondly, round bottle blow moulding is also the most adaptable to automated assembly lines, and the scale effect brought about by mass production is very considerable.

Fourth, economic benefits (market operation analysis)

Coke requires less of a storage environment, carbonated beverages do not have to be stored frozen during transport, and open shelving reduces marginal costs, offsetting the additional storage costs it entails. The benefits of designing into a square box are not higher than the benefits of designing into a round bottle for the consumer experience, which is one of the factors that influenced the design of the Coke round bottle.