You can use any clean, watertight vessel to decant (pour the contents of) a bottle into. A china jug would do but glass is provably inert and has the great advantage of allowing you to enjoy looking at the colour of the wine (especially attractive for white wines). Proper, traditional decanters tend to be glass with a narrow neck so you can pour them easily and with a stopper so you can decide whether or not to keep air out..
Decanters tend to come in single- or double-bottle (magnum) sizes. Antique ones can be unearthed from junk shops for relatively little money, especially since you don't strictly need a stopper for a decanter used only for serving. See Where to find antique decanters for some specific suggestions.
Spirits and madeira can be kept in a (stoppered) decanter virtually forever but port and even sherry tends to deteriorate after a week or sometimes less. Wine that has not been strengthened by alcohol is often worse (and occasionally, in the case of concentrated, tannic monsters, better) after 24 hours in a decanter.
To decant or not
There are strong practical reasons for separating a wine with sediment from that sediment, which can taste bitter and physically gets in the way of enjoyment. This traditionally involves standing the bottle upright for a day or two beforehand and pouring the wine into another clean glass container (glass is inert and if clear allows you to enjoy the colour of a wine, which can be a great pleasure) with a strong light source behind the bottleneck so that you can tell when the sediment is about to slip into the neck and can stop pouring at that point. That light source could be a candle or any strong light such as a desk light, table lamp without the shade or strip lighting under a wall-mounted cupboard. Bear in mind that some wines coat the inside of the bottle with a deposit that will not fall to the bottom of the bottle however long you stand it upright – but nor will it make the wine cloudy.
I often decant full bodied white wines which may have no sediment at all, simply because they look so gorgeously golden in a decanter. A glass jug or clean bottle would do just as well in practical terms. In the famous Locanda Cipriani on Torcello in the Venice lagoon, local fizzy white Prosecco is served in vast glass jugs.
Scientists say we should decant at the last possible moment so that no part of the wine's reaction with air be lost to us. As a host I confess I am prepared to sacrifice completeness for convenience with all but the most fragile old wines, say those over 25 years old, depending on their body and the style of the vintage. In practice therefore I tend to decant most wines that need decanting just before guests arrive, saving only really old bottles to be decanted just before serving.
Some young wines however are so tight and closed that, even though they are too young to have formed any sediment, they benefit from the aeration involved in pouring the wine from a closed bottle into another container. If I’m decanting for this reason, I’ll deliberately splash the wine as much as possible into a glass container with quite a wide neck – even the Graal decanter illustrated (rather amateurishly) on the left of the picture here that is sold by Spiegelau and looks like one particularly greedy giant wine glass with a pouring spout.
I also find a stainless steel funnel with a fine mesh, or a clean funnel with coffee filter paper useful for rescuing the wine from bottles into which corks have crumbled.
Here are some very rough practical guidelines for serious, reasonably expensive examples of the wine types cited below.
Decant immediately before serving:
Red bordeaux and Rhône more than 20 years old
Vintage port more than 50 years old
Decant 1-2 hours before serving:
Red bordeaux and Rhône five to 20 years old
Vintage port 10-50 years old
Decant splashily for maximum aeration up to 4 hours before serving:
Red bordeaux and Rhône less than five years old
Barolo, Barbaresco and Brunello
Modern Rioja, Ribera del Duero and Priorat
Bairrada, Dão and Douro reds
Vintage port less than 10 years old
Ambitious New World Cabernet and Syrah/Shiraz
Caring for glassware
Aesthetically, glassware needs to be clean, and has the annoying habit of being extremely breakable and showing every speck and dribble. The important thing as far as the taste of wine is concerned is that the glass smells of nothing - not washing up liquid (which can stop the formation of bubbles in fizzy wine), and certainly not dirty glass cloths. Many smart wine glasses, including much of the Riedel range, are perfectly happy in a domestic dishwasher and indeed benefit from the high temperatures there. Water has to be soft, however, and there is no need for detergent. Hand washing glasses achieves best results if glasses are washed in very hot water, rinsed in cold, and polished immediately with linen tea towels reserved for the purpose - I'm told. In an ideal world we would all have unlimited supplies of new, fine crystal glasses. See here and here for threads in members’ forum about cleaning glasses with considerable input from Riedel’s earthly representative in the UK.
Decanters are notoriously difficult to clean inside. Standing them full of a warm solution of denture cleanser can work. I’m also told that a product called Magic Balls, which come in small pots, cost very little, and are available from good kitchenware shops, do the job well too, although I have no first hand experience. They come with a small sieve ready to pour the balls into, rinse through and dry on kitchen paper before putting back into their little pot. These also work for wine glasses apparently, if you have hard water and they’ve turned milky in the dishwasher.
I am inviting comments on decanters, decanting and caring for glassware as I feel sure that others will have comments and tips.