Varadox

So I'm clearly being a dumbass and don't understand how creating Strong Wine works. I have multiple liters of the normal wine in both bottles and in barrels in my cellar. But when I let it sit there it won't ferment/cure. I feel like I'm missing something. I did a little experiment and just had one 1L barrel of it on my roof to see if it would ferment there quicker. Nope, just started to rot.