That makes me wonder about the examples of transparent plastic containers for plain milk. Do they have UV-blocking properties, even while they are transparent? I wonder how I could test that or find it out.

Cardboard milk cartons stop UV light from reaching the milk. I assume the same is true of the plastic containers and have a vague recollection of their being something added to plastic milk containers to stop UV light.

Water is immune to UV light.

Cardboard cartons are most likely rectangular because it’s much easier to produce from a flat piece of cardboard on an assembly line.

Obviously if there is a juice that is adversely affected by UV light it will be in a plastic or cardboard carton/Tetra Pak container.

Anything else has to do with marketing, costs and how the product is going to be used by the customer.

http://www.straightdope.com/columns/060616.html

It seems unlikely that the shapes of milk containers is designed to force sparseness.

-D

I am trying to remember enough of my physics to defend this position, but I am having trouble doing so.

Not that I know anything about these sort of things, but I would have expected the tightly-packed array of milk cartons to be counter to efficient refrigeration. I seem to remember reading that it is relatively inefficient to pack your freezer to occupy every cubic centimetre; maximal cooling efficiency is afforded by some air around the items to be cooled. (And I guess convection would be the source of air movement in this case).

However, just thinking about it some more now, the average supermarket refrigerator probably doesn’t rely on air movement for heat transfer. They seem to chill the milk cartons from below, and this would also justify packing the milk as tightly as possible.

This explains the difference in shape between cans and cartons: as a cause or effect of the different refrigeration techniques employed. In my experience cans are stored in more familiar, enclosed, refrigerators. These probably rely on air circulation to cool effectively.

What do you reckon? Sound plausible?

This book has a section that notes that beverages that are typically consumed directly from their containers tend to be in containers that are round. His rationale for square-ness for milk and roundness for soft drinks is as John describes: that soft drinks tend to be stored in cheap, open shelves, and milk tends to be stored in expensive refrigeration where they need to pack densely.

The section immediately after this ponders why aluminium cans are constructed inefficiently. Shorter, wider cans would use less raw material and presumably be cheaper to manufacture. The answer offered is that people perceive taller containers to be more voluminous.

But I digress…

2. I did some truck driving for a milk distributor a while back & was intrigued to see how much of the infrastructure was based on the design of the plastic milk crates. Factory conveyor lines, forklift trucks, loading ramps, all were designed to be compatible with moving rows of milk crates so they could be stacked efficiently into the trucks & warehouses without further packaging. I assumed that the size & shape of the milk cartons was also made to fit these crates.

3. I note Julian’s noting John’s use of Julian links. The quest is off to a good start! Julian links rule!!