Why Wine Bottles Have That Weird Dent at the Bottom

Next time you're finishing a bottle of wine, take a moment to appreciate the engineering marvel you're holding. That mysterious indentation at the bottom of the bottle—known as a punt—isn't a manufacturing quirk or a sneaky way to give you less wine. It's actually a clever structural solution that's been around for centuries.

The Physics of Glass Under Pressure

Wine bottles need to withstand significant internal pressure, especially sparkling wines like Champagne, which can build up to 90 pounds per square inch—roughly three times the pressure in a car tire. A flat bottom would create a weak point where pressure could cause the glass to crack or even explode.

The punt works like an architectural arch turned upside down. By curving inward, it distributes pressure evenly across the bottom of the bottle, dramatically increasing structural integrity. This same principle is why:

• Domes are stronger than flat roofs
• Egg shells can support surprising weight
• Submarines have curved hulls

A Holdover from Handblown Glass

The punt's origins trace back to when all bottles were handblown. Glassblowers used a pontil rod attached to the bottom of the bottle to hold it while shaping the neck. When removed, this left a rough, uneven scar called a pontil mark.

Pushing the bottom inward solved two problems at once. It hid the ugly scar and prevented the rough glass from scratching tables or causing bottles to wobble. Even though modern manufacturing has eliminated the pontil mark, the punt remains useful.

Beyond Strength: Practical Benefits

Sommeliers love the punt for pouring. That indentation provides a perfect thumb grip, allowing for the elegant one-handed pour you see in fine restaurants. The proper technique involves inserting your thumb into the punt while your fingers support the bottle's body.

The punt also creates a natural collection point for sediment. As wine ages, particles settle into the ring around the indentation rather than spreading across the entire bottom. This makes decanting older wines much easier.

There's even a temperature benefit. When bottles are stored on their sides, the punt's extra surface area helps maintain consistent cooling throughout the wine.

Does Punt Size Indicate Quality?

Here's where things get interesting. Many people believe a deeper punt signals a better wine. While there's some correlation—premium producers often use heavier, more traditionally-shaped bottles—it's not a reliable indicator.

The truth is that punt depth is more about tradition and marketing than quality. Some excellent wines come in bottles with shallow punts, while some mediocre wines sport impressively deep ones. The wine inside matters far more than the glass containing it.

That said, Champagne and other sparkling wines genuinely need deeper punts to handle their extreme pressure. So for bubbles at least, that deep indentation is doing real work.