A bottle of Champagne should be chilled (but never in the freezer) before opening. The ideal serving temperature is between 6°C and 9°C, giving a drinking temperature of 8°C-13°C once the wine has warmed up in the glass. Full-bodied Champagne wines —rosé, vintage and older, maderised wines — may be served slightly warmer (10°C-12°C) to bring out their bouquet.
The same serving temperature also applies to Champagne at the sweeter end of the scale, such as Sec and Demi-Sec. Serving these any colder will certainly attenuate the sweet flavours but in that case why choose a sweeter Champagne in the first place? Chilling to between 4°C and 6°C was common practice in the 19thCentury when Champagne was typically super-sweet. But if you serve a Sec or Demi-Sec Champagne at that temperature today (as recommended by some) you will simply lose the sweetness for which you bought them.
By far the preferred method to chill Champagne is to place the unopened bottle in an ice bucket, which should be filled to within roughly an inch of the top with half ice half water. Assuming an ambient temperature of 20°C, allow 40 minutes to chill a Champagne cellared to 11°C but at least two hours for a Champagne at room temperature — considerably longer in some special cases. The advantage of the ice bucket is that it brings a wine down to the right temperature gradually then keeps it there. The contents will stay at 4°C for two and a half to two and three quarter hours — roughly the same time as it takes for the ice to melt when chilling a 20°C bottle in a room with a 20°C temperature. But keep the ice bucket topped up just to be on the safe side.
If you dry the bottle as you remove it from the ice bucket, there’s really no need to wrap it in a napkin or tea towel as you pour. Whatever may be said to the contrary, this isn’t part of the Champagne tradition and may actually constitute a social faux pas if the napkin conceals the label. All of the bottle markings should remain clearly visible at all times, partly out of respect for the producer but also to show off the bottle in all its finery and let guests see the brand they are drinking. If you must use a napkin, tuck it under the bottle so as to leave the name of the marque in full view.
Only a complete philistine would think of chilling their Champagne in a competitor’s ice bucket.
If you don’t have an ice bucket, the refrigerator will do nicely — but be discreet about it. Place the Champagne in the part of the refrigerator that will give you the level of coldness you want, preferably laying the bottle on its side to avoid differences in temperature between the top and the bottom. Always allow more time when chilling in the refrigerator: two and a half hours for a Champagne cellared to 11°C, three hours for a Champagne at room temperature (20°C). Remember too that the bottle will only stay chilled for as long as it remains in the fridge. After that it will start to warm up — no such problem with an ice bucket. Alternatively, for a picnic say, a cooler bag can be extremely useful.
Champagne will keep in the fridge for several weeks so you can always have some handy, chilled to just the right temperature. But try not to open the fridge door too often or the resulting temperature changes could have an effect on the Champagne. So too could the smells in your fridge if you leave the bottle in there for too long. After about two months, there is a risk that these will seep in through the cork and spoil the taste of the Champagne. Restaurant cold stores suffer from the same problem. Hotel mini bars and custom wine cabinets, on the other hand, do the same job as a refrigerator but with none of the problems that go with it.
Note that people blessed with their own underground wine cellar, at a constant temperature of 10-11°C, can dispense with the need for ice altogether (unless they happen to like their Champagne super cold). Bubbly served straight from the cellar, as they do in Champagne, is chilled to perfection.