We are very fond of sweet wines. Often the word 'sweet' tells only part of the story - the best have aroma and freshness as well as more than usual sugar.
Mostly the sugar is the natural content of the grape juice. In most wine, all of it is turned into alcohol during fermentation. But in sweet wines, either fermentation is slowed down and stopped by cooling leaving some sugar, or alcohol is added to kill the yeast before all the sugar is used up, or sugar can be added to a dry wine - generally frowned on or prohibited, but it is allowed in Champagne.
In many cases, sweet wines are made by using riper than usual grapes - if they are late-picked they develop more sugar on the vine, and sometimes a special fungus - 'noble rot' - intensifies the sugar content still further.
There are costs and risks in using late-picked grapes - the weather has more chance to wreck a crop; riper grapes shrivel so you need more to get a given volume of juice; not all grapes on a bunch ripen at the same rate so you may need to hand-pick individual grapes (in French, vendanges passerillés); and if you wait for noble rot you sometimes get the wrong sort of fungus and the whole crop is ruined. So many sweet wines are relatively expensive.
Great sweet wines made from late-picked grapes include Sauternes and Barsac from Bordeaux, and many German wines from Riesling and other grape varieties. Some of our favourites from other parts of France are Coteaux du Layon and Bonnezeaux made of chenin blanc grapes, from the area south of Anjou in the lower Loire (these have astonishing keeping qualities for white wines and we have drunk 20- and 25-year-old examples which were delicious).
Closer to our new home and in the Rhône valley there are a number of well-known muscat vins doux naturels - the term is misleading since they are all made by stopping fermentation with alcohol, so are fortified like sherry or port. The best known of these is from Beaumes de Venise in the southern Rhône but Languedoc-Roussillon examples include Rivesaltes, St Jean de Minervois, Frontignan and our own local appellation, Muscat de Lunel.
Recently (July 2007) we have found wonderful sweet wines in Friuli in north-east Italy - Piccolit and Ramondolo are examples - and have realised that there are many wines in Italy like these which use late-picked grapes for sweetness but also enhance and concentrate them by partly drying the grapes before fermenting them. Obviously this produces still less wine from a given quantity of grapes!