Why is the paper box containing milk designed to be square?

Firstly, the need for shelf life (chemical analysis)

Milk, a perishable and difficult to store liquid, is mainly considered sterilisable and therefore needs to be packaged in a composite material called Tetra Pak. Tetra Pak packaging can increase the shelf life of milk to months or even half a year. Whereas Tetra Pak packaging is a composite material consisting of paper, polyethylene and aluminium foil, 70% of which is paper, this packaging material has similar strong properties to paper, which is most easily shaped into a square.

Secondly, storage costs (economic analysis)

Milk needs to be refrigerated in a freezer, and operating costs are raised. But refrigeration is unavoidable, so it is necessary to make full use of the freezer space by changing the shape of the milk box, indirectly reducing costs.

The choice of square milk bottles is understandable in terms of the cost effectiveness of economics. It is because of the difficult nature of storing milk that it needs to be stored in a freezer or refrigerator, whether in a shopping centre or at home. Square packaging maximises storage space, reduces operational and transport costs and increases space utilisation.

Third, technical constraints (process analysis)

One might say, why not make a round bottle out of paper then?

First of all, most people do not drink milk directly from the box, and even if most people drink milk directly from the box, they are unlikely to sell it in a cylindrical container based on the cost effectiveness principle.

What is the cost effect principle, the only time you should do this is if the additional effect of the action outweighs the additional cost.

Secondly, with a material like paper, the easiest structure to make is a four-sided shape. A few indented lines of folding and a sheet of paper will make the body of the jar and the top and bottom lids. If you want to make it round, the body is easy to do, just roll it, but the closure at both ends would be very complicated, not easy to fit, basically impossible to automate, and very material intensive, so paper boxes are rarely made round.

By the way, there are two basic concepts:

1. with the current state of technology in industrial production, we cannot yet mass produce any shape of packaging, even the most common glass, plastic and paper. Some very beautiful packaging (let's say Sassoon) is produced at a very high end-of-life rate, which leads to a correspondingly high cost.

Even so, mass-produced products are heavily compromised compared to prototype designs, mainly due to cost and technology.

2. Changing the shape of any FMCG packaging is an enormous investment. (typically in the millions of dollars)

① For example, to change the shape of a bottle cap, several sets of plastic moulds have to be re-invested (ranging from several hundred thousand dollars each)

②Changes to the bottle body will generally lead to renovation or re-investment in the filling line (ranging from several hundred thousand to several million dollars)

③First of all, consumers do not necessarily buy into the change of outer packaging, so the packaging change itself is very risky.

④ corresponding changes in shipping, shelving, advertising, posters, etc. (ranging from several hundred thousand to several million dollars)

So, for the vast majority of companies, when there is a new product on the market and they have to choose packaging, they generally look at what style of packaging design is available for similar products on the market and then choose packaging that is already well established on the market and modify it slightly.