To understand what makes Madeira wine so unique, we must travel back to meet the conquistadors of the 15th Century.
The early Portuguese settlers already started a wine production, mixing wild grapes found on the island with sweet Malvasia grapes brought over from Crete. The Madeiran wine trade started mainly in the East Indies, but during the long journey the wine was completely spoilt, almost unfit for human consumption, therefore not so popular in the foreign market.
Then the Portuguese settlers thought about adding a small amount of distilled alcohol made of sugarcane, the same method they had been using for making Port. This way the wine was able to travel far without being spoilt. The only problem was that people in the East Indies still associated Madeira wine with a vinegary, undrinkable slipslop, therefore a large quantity was sent back to Madeira.
At this point, the wine had spent a good few months travelling on ships, then stood in vain in the tropical Indonesian heat just to be put on a ship again and travel all the way back to its home. The wine was heated up and cooled down over and over again, and when the barrels were finally opened in the ports of Madeira, the sailors knew that they just discovered something exceptional.
The winemakers quickly realised that aging the wine on the sea voyages would be a very costly production, so they started to build so-called estufas, or chambers that were heated up by the direct sunlight.