What Do the Various Colored Dots on Beer Can Bottoms Indicate?

When you’re reaching for a can to make PBR beer-can chicken on the grill or filling your cooler with canned beers for guests to crack open at your next backyard party, you may notice a curious speck of color painted on the bottom of each can. While a can’s design may be aesthetically pleasing, this haphazard detail on the can’s surface may cause pause. No, this mark is neither an indication of a faulty product or an invitation to participate in some underground money-making game show. 

Efficiency can translate into profit in high-turnover industries. If a spray machine happens to misfire when beer cans are produced, product that can’t be sold has to be handled while producers are left to stop assembly to figure out which machine is responsible for the faulty pattern. If a spray machine starts spraying cans with the wrong design, that could mean 300 cans made in a single minute that are mislabeled and then must be recoated or discarded. Since aluminum cans are cranked out at high speeds, these small painted marks on the bottom of cans help manufacturers keep production lines moving if a particular machine begins to act haywire. 

As a protective mechanism, manufacturers can install controls to monitor ink guns affixed to machines that control both size of the dots and whether multiple dots are marked on an individual can. In what is called the Nordson Ink-Dot system, a spray gun is affixed to the outside of the spray machine. This Ink-Dot gun is equipped with a sensor, so the ink spray is triggered when there is a can placed in front of the unit. 

Before the can enters the machine, this small marker is painted onto each can. Some dots can only be seen with ultraviolet light, but many others are marked with an assortment of colors. Different colors represent different machines so any messed up coatings can be quickly identified so that when there is an error, only the responsible machine has to be attended to instead of a complete factory-wide shut down. So, as tempting as it might be to come up with conspiracy theories about these random-looking marks, they are simply there to help keep production on track.