Answer: Punt

If you’ve handled a wine bottle before, especially a champagne bottle, then you might have noticed part of the bottom has a noticeable indentation in it. Not all bottles have it, and cheaper bottles of wine tend to have simple machine-molded bottles that lack it (or have a very subtle version), but the dimple in the bottom of the bottle is a long-standing fixture of the wine bottle.

The purpose of the punt has a long and storied history littered with clear-cut facts and more than a little bit of folklore. Let’s start with the facts of the punt. The term is most certainly a transfer of the name of the tool used to create the shape in the bottle. Glassblowers use a tool called a “punty” (also referred to as a punty rod, pontil, or mandrel), which is a rod-like tool used for shaping glass and transferring pieces. The spot where a glass piece is attached to the punty is called the “punt mark”. When hand blowing wine bottles, the most obvious place to attach the punty to the bottle would be the base, deformed slightly inward so that the punt mark would be hidden away where it couldn’t make the bottle unstable or scratch the table the bottle was set on. Thus, the place on the bottle where the punt mark was located simply became known as the punt.

That’s one practical reason for the punt existing. Here’s another: the punt strengthens the bottle. There’s a reason champagne bottles have a deep punt and are made with thicker glass—both help the bottles maintain structural integrity in the face of higher pressure levels. Champagne bottles are also “riddled” (a special process where aging champagne bottles are gentled agitated), and the deeper punt on the bottle makes it easier for workers to quickly grasp the bottle and agitate it. Historically, a deep punt also served another practical purpose. While modern wines are well filtered and fairly sediment free, older wines had fairly high levels of sediment and the base of the “hill” inside the bottle created by the punt provided a place for the sediment to settle so that, with a careful pour, you could avoid the sediment ending up in the glass.

Now for the less substantiated and practical claims about the punt. Some people claim it helps decrease the chilling time by increasing the surface area of the bottle. That’s technically true. The punt creates additional surface area, but that increase in surface area is pretty small and hardly has a noticeable impact on the chilling process. There’s an old folk tale that says the punt was there so that tavern owners could bang it down on a steel pin behind the bar, ruining the bottle and preventing anyone from refilling a bottle used for good wine with cheap wine and passing it off as a higher value product. That seems like a lot of messy glass-shard filled work and there’s not a whole lot of historical evidence for it. There’s also a claim that the punt is there to help stack bottles on ships, but it’s easy enough to crate bottles of wine without the hassle of trying to stack them like cups, so again, not a lot of historical merit to that claim either.

In the end, the punt is an artifact of early wine bottle making that we’ve preserved today for use in champagne bottles and fancier bottles of wine, but modern bottle crafting has largely rendered it obsolete. When you see it today, it’s largely a matter of tradition and history since it’s fairly trivial to make a strong flat-bottom bottle with modern techniques.