Dutch interest in the transport of and trade in wines helped shape the evolution of wine production according to the dictates of changing taste and the requirements of the long-distance transportation of a perishable product by sea. Until the end of the 17th century, most wines could not survive from one vintage to the next, and many were spoiled and undrinkable within six months of the vintage, partly because they were transported in large oak casks, ‘tuns’ of 900 l weighing 1,000 kg, inclusive of the wood, which constituted the units of freight. Even before the creation of overseas colonies, wine destined for the Baltic had to overwinter at some convenient point. The grape harvest occurred too late in the year to permit immediate transportation to the northern lands, since the Baltic and White Seas often became impassable from November onwards. To overcome these disadvantages the Dutch popularized mistelles, wines fortified by the addition of brandy to stop fermentation and prolong the life of the wine, and vins pourris, made from overripened grapes. They also introduced the French to the stabilizing effects of sulfur candles (known in French as allumettes hollandaises for many years), and encouraged the production of distilled liquors, based on both grain and grape. Amsterdam and Rotterdam became the principal international markets for wines and brandy in the 17th century, sustained by regular and reliable supplies, bulk storage, and an international network of merchants. One effect was the increase in planting white grape varieties in western France, to satisfy the tastes of the Dutch market.