Periodically over the years, a random consumer will notice a small ink dot on the bottom of a beer can and take their confusion online. Sometimes, the queries fade into obscurity on an innocuous forum thread; other times, curiosity will briefly surge at the hands of a viral TikTok video. But, as is so often the modus operandi of the internet, the resulting answers on why there are different color marks under beer cans vary in their plausibility. There are theories that involve different flavor profiles corresponding with different colors or colors specifying the manufacturer — some have even posited that the dots indicate beer that has been mixed with chemicals and the dot covers a syringe mark, or that one particular color will give you superpowers. The truth, however, is much more mundane and purely industrial.
If you find a mark on the bottom of a beer can, it means that the manufacturing company used an ink-dot identification system. Each machine that sprays coating on the cans is given a different color. If one of the cans emerges with imperfections or errors in its coating, the manufacturer will be able to look at the little dot on the bottom and know right away which machine it came from and which is producing the problems. It saves time and money if you don’t have to shut down production entirely to identify the issue.
A colorful solution to industrial glitches
Putting beer into aluminum cans involves washing the cans and filling them with carbon dioxide to force all the oxygen out (oxygen will make the beer go bad more quickly and taste more stale). Then, the beer goes in, the can top is added and sealed, the exteriors are cleaned, and the cans are labeled. The ink dot marking actually comes into play even earlier, when the cans themselves are being created. In most cases, after the cans are cut out, shaped, trimmed, washed, varnished, and set in an oven to bake, a machine sprays a protective coating on the interior of each can. It’s this machine that typically gets its own different color mark.
The polymeric coating sprayed inside the cans plays an important role. It acts as a barrier between the metal can and the beer inside, keeping the metal from corroding, protecting the drink, and affecting how long beer lasts in the can. If that spray machine malfunctions, the can and the beer could degrade more quickly — identifying the faulty instrument is important. And, all the operator has to do is flip the beer can upside-down to find the colored dot so they can locate the offending appliance.
