Trivia 044: Cracking open a cold one

There’s not much better than getting home from a long day, and cracking open a cold drink. Of course, I’m talking about soda. What else would I be talking about? Personally, my favorite soda is Dr. Pepper. Entry 003 discussed some early history of Dr Pepper, and you can look forward to another post featuring the best soda later this year. But that’s not the point of this particular entry. Today I don’t want to talk about the delicious interior of a can of soda, but rather the can itself.

Soda cans have a quite ingenious design. They’re the result of decades of improvement, trying to find the shape which best satisfies three main criteria:

1. How do we use the least amount of material in order to store our liquid? Well, the best answer to that is to use a sphere. Spheres have the highest volume to surface-area ratio of any 3D shape. This means that in order to hold the same amount of liquid, a sphere shaped container will take less aluminum than a cube shaped container. However, spheres do not really make for convenient containers, both because they’re not the easiest to hold.

2. What shape is the easiest to pack and transport? If you pack spheres into a box, you’ll actually only use up about 74% of the space in the box. This is known as a packing problem. The shape that is able to fill a box best is a cube (or rectangular prism). But, again, you’ll be using more material. In addition, rectangular prisms have corners and seams, which are weak points.

3. How do we store liquid which is under pressure without it exploding? Carbonated soda cans can have pressures ranging between 30 to 50 psi (depending on if it’s been shaken). In comparison, atmospheric pressure is only about 14.7 psi. Even non-carbonated drinks are pressurized, to help strengthen the can.

The best shape which satisfies these criteria is a cylinder. Cylinders have a high packing density (about 91%), while also retaining the structural strength of a sphere. In addition, cylindrical cans can be manufactured quite easily. All sorts of other innovations have gone into perfecting this shape, such as the domed bottom, the tapering of the neck, the double steel of the top, and, of course, the pull tab to open.

Pretty much every can we see in our day-to-day lives takes advantage of these refinements in design, perfected over many years. However, not all cans are the same. In particular, if you go to Hawaii, you might notice that many of the cans there have ridged necks. This is because the state of Hawaii only has one can manufacturing plant on the islands. While they do import some soda cans, it’s a lot cheaper to make and fill the cans on the islands, rather than transporting them all the way from the mainland. The Hawaiian-produced cans have ridged tops to make them consistent with local distributors. Replacing all the equipment which relies on these can sizes would be much more expensive than just using these slightly larger cans.

So next time you pop the lid on a can of delicious brew, consider the amount of thought and design which went into the humble can you’re holding. And please, don’t forget to recycle.

If you know anyone who would like to receive these, please have them send an email to [email protected] And if you only drink diet soda, let me know and I can take you off the list.

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