Vintage Ports are only made on very exceptional years (usually three or four times in a decade).
The principal determining factor is the weather in the vineyards which must be ideal throughout the viticultural season and subsequently during the harvest.
Only a few exceptional vineyards in the Upper Douro region produce wines of sufficient body and style to make a true Vintage Port.
After the harvest, wines of Vintage potential are put into oak barrels called 'pipes'. Some eighteen months later a careful and painstaking series of tastings is held to judge exactly which wines of different vineyards merit inclusion in the final blend. If the ideal blend is achieved, the wine is then bottled without any filtration whatsoever approximately 24 months after the original harvest .
Vintage Port must then be matured for some ten to twenty years in cool dark cellars as it gradually achieves the outstanding style of a great wine.