The Art of the Soda Can

How often do you crack open a can of soda or soup? Have you ever thought about the amount of design that went into such a frequently used device? When the aluminum soda can was first being invented the shape of the can was strongly considered. The benefits of a spherical can were that it would use the least amount of surface space and there would be no weak points in the design of the can, other than the opening. A spherical can have many disadvantages though, it would leave lot of empty space in packaging, it wouldn’t be able to stand upright, and most importantly it would be difficult to manufacture. A simple answer to most of these problems would be cuboid can. This can would be able to stand upright by itself and be fairly simple to manufacture. A cuboid can has weak edges at the corners and is difficult to hold comfortably. A healthy middle of a spherical and cuboid can was a cylindrical can shape.

Aluminum cans are made using a series of dyes and presses, and they are most commonly manufactured in a production lines. The can starts off as a flat circle aluminum and are pressed into a small cup first, the walls are then stretched upwards in three different steps to make the height of the can more reasonable. After the neck of the can, or the little indent of the can, is developed the top is worked on. Before I talk about the double seam on the top of the can I would like to draw attention to the dome shape at the base of the can. This dome helps to distribute the weight and pressure of the product and make the packaging more durable. Though most cans of soda will only experience pressure changes of 1-2 atmospheres, they are built to handle 6 atmospheres of pressure. The top aspect of the can is the most impressive part, because it is so simple yet so precise and functional. The engineers came up with a double seam that can be seen in the image below. To assure that no extra gases leak out and to maintain the pressure in the can most manufacturers will add an extra compound that solidifies to form a gasket. The lid of the can is added immediately after it is filled so that the lid can trap the gases and maintain the necessary pressure.

The last feat of the can, which is what sparked my interest in the first place, is the pop tab. This was not a feature of the first can invented. The first can had a flat lid and required a special opening tool that would press in one hole for drinking and another hole for venting and allowing a proper vacuum to occur. The next can that came out around in the 1960’s had a pull tab that would just be torn right off the top of the can to create an opening. These worked well for opening the cans but they caused litter and injuries to barefoot beach-goers or wildlife, as they would leave a very sharp tab sticking up from the ground. Finally came the modern pop-tab that works as a second stage lever, pulling open a little bit of the can where it’s fastened on, then once the seal is broken and the pressure is released it becomes a first stage lever, pushing down on the lid of the can and forcing it to break inwards.  

At the end of the day soda is bad for you, but still incredibly popular as a drink. Furthermore the soda can is ubiquitous at parties and gatherings, and even in the common American household. I doubt that anyone often considers the science behind this can, and I applaud the people who have previously dwelt on the concept because it seems like such a simple idea and it has somehow been so well perfected over time without a big fuss being made. Of course when the first can’s with pop tabs came out people were excited not to need a can opener, but I feel it is something that we seldom appreciate in our day to day lives.

The Ingenious Design of the Aluminum Beverage Can