A wine bottle consists of the glass bottle, front and back labels, a stopper (cork, synthetic or screw top) to close the bottle, and a capsule or foil to cover that stopper.
Most wine bottles are 750 milliliters in size. They were originally called "fifths" because they contained a fifth of a gallon. Now wineries all use the metric system.
Split (half-bottle)—375 ml
Magnum (two bottles)—1.5 liters
Jeroboam (double magnum - four bottles)—3 liters (sometimes 4.5 or even 5 liters)
Rehoboam (six bottles)—4.5 liters
Methuselah (Imperial - eight bottles)—6 liters
Salmanazar (twelve bottles)—9 liters
Balthazar (sixteen bottles)—12 liters
Nebuchadnezzar (twenty bottles)—15 liters
The covering on the top (the neck) of a wine bottle is called a foil or capsule. Its purpose is to further seal the bottle opening and prevent leakage of wine or entry of air into the bottle. Originally the foil was made of metal, usually lead. The industry stopped using lead in 1993 to avoid the possibility of traces of lead ending up in the wine glass, and of contamination of landfills.
Today the capsule is made of tin, plastic or even paper. Should you encounter an older bottle of wine that has a lead foil, after removing the foil, carefully wipe the top of the bottle to remove any possible traces of lead before opening and pouring the wine.
For centuries, corks have been used to plug the opening of a wine bottle. Corks come from the bark of cork trees, usually from Portugal or Spain. Corks trees are around 35 years old before their bark can be used to make corks. It then takes another 7 to 10 years before the bark can be stripped again.
A cork prevents wine from spilling out of the bottle and most air from entering into the bottle.
However, corks vary in quality and can deteriorate over time. Eventually they can shrink enough to allow excessive air to enter the bottle, which negatively affects the taste of the wine. Corks can also develop mold. Wine with the taste of a moldy cork (or "wet newspaper") is said to be "corked."
Today more and more wineries, even ultra-premium wineries, are switching to corks made of plastic or a composite material, and even to screw tops.. While some purists still deride the change, the reality is that these solutions can prevent all of the problems associated with natural corks, with no apparent negative effects on the wine itself.
Inspecting the Cork
When the waiter at a restaurant opens a bottle of wine at your table and gives you the cork to inspect, you may, if you wish, sniff the cork to see if it smells okay. (In some restaurants the wait staff will snicker from a distance if you do it.) But it makes a lot more sense to simply try the sample of wine the waiter has just poured you, since you paid for the wine and not the cork.
The actual reason you're given the cork is historical rather than functional. There was a time in Europe when restaurants would attempt to pass off cheap wine as premium wine. To counter this, wineries started imprinting their name on the corks so that the customer could inspect the cork and see that it really did come from the winery whose wine he had requested.
Keeping the Cork Moist
When storing a bottle of wine, keep the bottle on its side, with the top a little lower than the bottom. This will keep the cork moist, and prevent it from drying out and allowing air to enter the bottle. (If your bottle has a synthetic cork, or screw top, this isn't necessary. The stopper won't dry out.)
The punt is the concave "dent" in the bottom of the wine bottle. There are a number of explanations as to why the punt is used. One is that in centuries past, it was created to provide more strength to bottles under pressure—champagne bottles. It then began to be used by all wine bottles.
Another explanation for its current use is to trap sediment along its edges as it sinks to the bottom, although most U.S. wine today is well filtered and has little, if any, sediment.
Another possible explanation is that in the days of hand-blown glass, leaving a concave dent in the bottom of the bottle minimized the possibility that the glass blower would end up making the bottom of the bottle concave, and thus unable to stand upright on the table.