by khoomeizhi on Fri Sep 09, 2016 5:47 pm
i'll see if i can help.
first, i don't have any experience with storebought yeasts. if you think you've found one that will work for you, go for it. (although, this place being what it is, have you considered using wild yeast?)
the link you have after asking about hydrometers has scales on it. hydrometers measure the specific gravity of a liquid, not weight. is that the right link?
when using fruit, the usual process is to have it in an open-topped (but covered with cloth or something most of the time) vessel for primary, so it's easier to access to stir and punch down the fruit. the fruit won't rot if it gets punched down a few times a day, and young wines/meads benefit from aeration in the early stages. by somewhere between 4 and 10 days or so, i'm usually straining things into a carboy with an airlock for the rest of fermentation.
mineral water vs tap, dunno. it's possible tap water could add some off flavors, but you won't know 'til you try. the difference may not be noticeable enough to make the expense worthwhile.
as far as i know most commercial yeast packets are supposed to be good for anything up to 5 gallons - so 5L should be fine.
just fermenting sugar water? yeah, that'll probably taste pretty bad. partly because the mixture is totally devoid of nutrients, so the yeast, if it does survive enough to make alcohol, will be stressed and making off-tastes and smells, as well as 'hotter' than usual alcohol flavors. you could fix that somewhat by adding yeast nutrient, but it would still probably not be very pleasant.
when it's all finished, the usual thing is to wait long enough that all the yeast and other particles in suspension drop out, then you rack the clear liquid off the dregs and bottle it. and then wait some more! generally the more alcohol in a wine or mead, the more aging it'll need before it's 'good'. with mead they usually say age one month per % alcohol. that's not a hard and fast rule, but consider that instead of insisting on making a 15% beverage that may be harsh for a while, you could aim a bit lower and be drinking something more tolerable sooner. just because a yeast *could* go to 15% - with proper handling - doesn't mean it has to. and it can be difficult, especially for a beginner, to take a yeast all the way to its limit. there's nothing really less cool about a 12% wine, when you come down to it.