There are two popular theories:
1) It was used to help align/stack bottles of champagne at a downward angle to help with riddling (shifting the bottle a slight turn every so often to move the sediment up towards the cork for later removal).
2) It helps to consolidate the sediments in an older wine so that less of the sediment is poured out with the wine.
I’ve poured a lot of wine in my life, from bottles both with and without punts, and still don’t know if there’s a right answer to this question. It is often used (along with a slight inwards taper to the bottle) as an indication of a “better” bottle of wine.
I think that the true reason behind why they have punts may have been lost over time, I have yet to see conclusive evidence of the numerous theories that get argued over.
Off the top of my head, some of the ones that I have seen are;
* Balance - It is proposed that older, hand blown bottles may have been prone to tipping over, the punt acted as a stabiliser.
* Strength - I have seen it said that the punt gave the bottle an extra measure of structural integrity (although I have also read some convincing arguments against this).
* Part of the process - The still-warm blown bottle would be placed on a rod to cool, making an indentation in the base OR The bottle would be spun on a rod while being blown into shape, causing an indentation in the base while it spun.
* Champagne - Once or twice I’ve seen someone mention that it made Champagne bottles easier to stack while undergoing production with sediment falling into the neck to be dispelled.
* Sediment - Some say that the punt assists in either forming or collecting sediment from red wines.
As to some reasons why they are still in use;
* Tradition - As well as making it easier for the bottle to be held horizontally in a neat manner while pouring.
* Marketing- The larger the punt, the larger the external size of the bottle can be made while still holding 750ml. This can give the illusion that a wine is of high quality because of the weight/size of the bottle.
I probably missed one or two, everyone seems to have a different idea.
The Champagne stacking one is a popular rationale, though it obviously only makes sense for sparklers.
I tend to favor the balance explanation. The ability to shape bottles with molds has been around since the early 18th century, but if you had a perfectly flat bottom, and there was an imperfection in the blowing (even with molds, people were hand blowing the glass into the mold), it would readily wobble. Imagine an otherwise flat surface with a slight protrustion.
The aforementioned Part of the Process is the truth, and since The Punt (or Kick, or Kick-up) has always been there so it shall stay. The punt also alleviates some pressure on the bottom of bottles during the corking process, and the second in-bottle fermentation of “Methode Champenoise.”
Sommelier – Alpine CC, NJ
Before wine bottles were moulded, they were
blown. After the bottle was finished the soft
bottom was cut off,leaving sharp edges if left
to cool. The still soft glass was pushed up
inside to prevent cutting people and table tops.
P.S. for “L.B. Vittes” post.
This info.was given to me by a champagne
maker in Reims.