This is why many wine bottles have a ridge at the bottom.

Increased stability due to tank pressure

Filling wine bottles causes the pressure in the bottle to increase. In sparkling wines, the pressure is even higher due to the added carbonic acid or the second fermentation in the bottle. The curvature at the bottom of the bottle means that when opening the bottle, the pressure is more evenly distributed over the entire glass surface, not just the bottom of the bottle.

Wine bottles can be cooled faster

Unlike a flat bottle bottom, the curvature at the bottom of the bottle creates an overall larger glass surface. In a water-filled ice bucket, cold water in contact with the glass surface of the bottle cools the wine. The larger the glass surface, the greater the cooling effect.

Better control over sediment

Red wines often have a proportion of solid particles called sediment. If the wine bottle is upright, this sediment settles to the bottom of the bottle. The curvature helps ensure that when the bottle is poured, this sentence is mixed as little as possible and does not go into the glass. Particles stay longer at the bottom of the bottle when pouring.

Optical illusion of bottle size

Due to the curvature of the bottom of the bottle, there is less liquid area at the bottom of the bottle than at the top. As a result, the glass bottle needs to be slightly higher so that, for example, 0.75 liters takes up no space. The larger or taller a wine bottle, the better its visual impression.

Easier handling while pouring

The curvature at the bottom of the bottle allows you to fix your thumb in the depression as you pour the wine bottle. This allows the wine to be poured without having to grasp the bottle with your whole hand. Some think that pouring into the bulge with your thumb is the most elegant way.