HI If you want I can give you some links I found about port, and a post I asked(brought up on degasing post) about it, or I coul;d copy, and paste the posts.
When I got a stuck fermentation after I racked my grape blend, and after I watered down(2 gallons out of three) for the yeast starter(raise PH native grapes pure juice/skins{tart/acidic}) that yeast starter was not working I thought after a hour so I went to the store, and got a 1.75 litre of cheap vodka-----(cheap, and Im glad I did so mostly because it's neutral)---- I raised the sugar 1.020, and the whole bottle droped it down to 1.010 I wanted it more dryer, but this expert wine brewer suggested not to blend it next year he said port should be thick,oily
He also said port can be above a certain percentage(I forgot) that must be why I see recipes for it with no fortifying agent.
20ml - 13% wine + 1ml 40% brandy = 14.3% port
20ml - 13% wine + 2ml 40% brandy = 15.4% port
20ml - 13% wine + 5ml 40% brandy = 18.4% port
I also have info about how much sugar raises the
SG. 2 cups finely granulated sugar = 1 pound =1.045 in a US gallon 4 cups finely granulated sugar = 2 pounds = 1.090 in a US. gal. of water
I think you could do the math, but I raised a 5 US gallon batches SG 0.030 with a 5 pound bag of sugar due to a low starting SG--- out of sugar for the forced yeast strater= (carrot wine).sugar probaly didn't dissolve all the way