Ice wine is a type of dessert wine produced from grapes that have been frozen while still on the vine. The sugars and other dissolved solids do not freeze, but the water does. When the frozen grapes are pressed, this creates a more concentrated, very sweet wine.In Ontario, Icewine must be made from approved grape varieties; the most popular are Vidal Blanc, Riesling and Cabernet Franc.The season starts with netting the grape vines in the fall, to protect the grapes from being eaten by animals or birds. Grapes are left on the vine until a temperature of -8°C or lower is reached (sometime between December and February), which means that the grapes may hang on the vine for several months following the normal harvest. If a freeze does not come quickly enough, the grapes may rot or be eaten by animals and the crop will be lost. If the freeze is too severe, no juice can be extracted. The longer the harvest is delayed, the more fruit will be lost. The grapes must freeze naturally to be called ice wine. Some winemakers use mechanical freezing to simulate the effect of a frost and typically harvest the grapes earlier. These non-traditional wines are sometimes referred to as "icebox wines", but not official VQA ice wine.Wineries carefully watch the weather, waiting for the optimum stretch of temperatures between -10°C and -12°C. A large labor force and a period of at least six hours is needed to harvest and press the grapes, usually during the night. Many wineries still harvest by hand. The grapes are harvested and pressed while they are still frozen, leaving most of the water behind as ice. Only a small amount of concentrated juice is extracted. Juice yields for Icewine grapes are much lower than for table wines—only 15% of the expected yield for grapes harvested for table wines. This reflects both the losses in grape volume from dehydration while the grapes hang on the vine, as well as losses to hungry animals. It is also the reason ice wine is generally more expensive than conventional table wine.The juice is very sweet and can be difficult to ferment. Because of the high sugar content, the fermentation stops early, leaving relatively low alcohol and high sugar levels in the finished wine. It may take months to complete the fermentation, compared to days or weeks for regular wines.Ontario has produced Icewine since 1984. Since 1991, Ontario has been one of the world’s leading ice wine producers. Ice wine production is limited to regions where the necessary warm summers for growing and cold enough winters for freezing are regular. Canada and Germany are the world's largest producers of ice wines. About 75 percent of the ice wine in Canada comes from Ontario.Icewine production is regulated in Ontario under the VQA Act and regulations. Strict standards are monitored by VQA inspectors, from vineyard to the bottle. Rules cover grape varieties, harvest procedures, winemaking and testing before the wine is released.