Many wine bottles and especially sparkling wine bottles have a more or less large indentation in the bottom (also a bottle insertion, French culot de bouteille). There are several opinions about the practical reasons. The curvature probably dates from the beginning of production, than that bottles not in exactly the same form as today and this indentation gave better stability and stability. According to another variant, the curvature was created when blowing glass because the bottle was turned over a wooden stick. The fact is that the arched bottom gives the pressure better to the walls and ensures that the bottle bottom doesn't break. The argument that the bottles of "Bouteilles stockées sur Pointes" (head to bottom) could be packed more stably is also correct.
Another advantage is that during the bottle aging especially with red wines, the precipitates get into the small groove around the indentation. As a result, the agitation of the depots prevented. If the indentation is deep enough, this can be used as a base for the thumb when pouring. The indentation is mandatory Bordeaux and champagne bottles, but also with many Burgundy bottles. Schlegel bottles and carboys, For the manual remuage A sparkling wine is used as a positioning aid for the remueur by many producers on the bottle bottom Winery point appropriate.
There is an interesting story at the champagne house Roederer, For the Russian Tsar Alexander II (1818-1881), special champagne bottles were produced for the Cristal brand, which is still produced today. The crystal glass had to be transparent in order to be able to quickly recognize poisoned champagne. In addition, there was no bottle indentation to prevent a small explosive device from being attached to the indentation in the bottle base. The bottles for the Cristal are still produced this way.
Image: Norbert Franz Josef Tischelmayer