I have a batch of freshly crushed touriga grapes, that I plan to turn
into a port. It has an initial brix level of about 25, but I'm
planning on adding enough sugar to get the alcohol level up to the
limit of the yeast that I'm using (about 18%). When I compute the
amount of sugar to add, should I base it on the expected volume of the
finished wine, or should I base it on the volume of the current must
(which obviously contains seeds, skins, etc.