As you might have noticed, the bottles of bubbly on your local shop’s shelves tend to be significantly heavier than those other bottles of basic red and white. No, this isn’t some strange coincidence, and no, you’re definitely not going crazy. Heavier sparkling wine bottles are most definitely a thing and are 100 percent bottled that way on purpose. Here’s why:
It’s actually quite simple: pressure, pressure, pressure! Champagne (and sparkling wines made in the méthode champenoise style) undergo a secondary fermentation within the bottle. Taking into consideration that carbon dioxide is a byproduct of fermentation, the gas remains trapped within the bottle, hence the reason your wine sparkles. This trapped gas needs a thicker, heavier vessel to withstand all that pressure caused by secondary fermentation. The classic Champagne-style bottle is similar to that of a Burgundy-style bottle, with slightly thin, slanting shoulders.
So what’s the deal with that little dip in the bottom of the bottle? That’s not an accident, either! This little indentation, known as the “punt,” gives additional strength to the heavier glass bottle. The punt also aids the winemaker during the riddling step of the winemaking process. Riddling is an imperative step in méthode champenoise-style winemaking, in which the bottles are gently turned every other day to shake the lees to the neck of the bottle.
By: Vicki Denig
***Grabbed from: https://vinepair.com/articles/champagne-bottles-so-heavy/