The Purpose of Beer Bottle Bumps
Many people have noticed the small bumps on the side of beer bottles, near the base (the “heel”). They’re not just on beer bottles either, every glass bottle in my house has them, which are mostly beer bottles.
These are typically called “mold codes” or “heel codes” and there are many different ideas about what these are for, but I could only confirm one.
It is a popular notion that these bumps help the bottler know how many times the bottle has been reused. I couldn’t find any proof that they are used for this. In fact, I’m not sure how these dots would convey that information since they are made when the bottle is molded.
This rumor seems to confuse the heel code with bottle date codes, which are traditionally found on the neck of the bottle. On newer bottles, date codes are stamped with ink. On older bottles, they were part of the glass mold and were often beside an embossed logo from the glass producer or bottler. Dating on older bottles helped bottlers know how long they had been in circulation.
I have read that heel codes are read by production equipment so the machines know how large the bottle is for proper filling and shipping. I could not find any concrete proof of this, but considering the next point, it’s certainly possible.
There are machines that measure many different bottle attributes to determine the quality of the bottle. If a bottle does not meet the quality standards, an associated machine will read the heel code from bottle. This makes a lot of sense because the bumps actually refer to the mold that made the bottle. So, if there is a quality problem with that bottle, the mold can be inspected for damage or wear.
Written By: Chad Upton