Vodka = Neutral Spirits + Water.
Neutral spirit is closer to something you would find in a science lab, than a liquor store shelf. It's just alcohol. It looks like this:
With all the heavy taxes on liquor, it's cheap and easy to buy everclear, dillute it 50/50 with water, and you've got ~45% ABV vodka. It doesn't taste nearly as good as a "real" vodka, but it's not too far off from the crappy ones you find on your liquor store's bottom shelf either.
Read up on making vodka- basically, you distill neutral spirits, and then add water. This is what ALL of the distilleries do. The guy who said that vodka only comes from potatoes, I dunno where he gets that from. It'd be like saying oil only comes from the desert. Go walk around any liquor store and many labels will say, "distilled from grapes"; "100% potato vodka"; "vodka made from grain" etc... As long as you have alcohol ready to distill, you can create vodka from it. It doesn't matter what you use as a sugar because the goal is a "neutral" spirit- that means you're trying to strip out all the flavor from the base ingredients. You can even distill wine and create neutral spirits from that. Some french vodkas do that- they use second-rate wine grapes. But really, it matters little because the goal is to get rid of all the flavors and just wind up with pure 100% ethyl alcohol. Of course, that's not possible, you only wind up with about 80-90% alcohol, but 100% is what you're
trying to achieve.
But the idea that 10% of the volume gives 90% of the flavor is sort of accurate.. assuming you aren't dilluting it with water. Afterall, ethanol is tasteless, so it's that other 10% that is imparting flavor, be it fusel oils, methyl alcohol, or some sort of flavor compound from the mash. Whatever, it's that 10% (in 90% ABV neutral spirits) that's giving you all of the flavor. Normally though, vodkas are cut, roughly 50/50 with water to bring it down to 40% ABV (80 proof). It's just kind of the standard practice.
So the flavors, from one brand of vodka to the next come from two factors: the purity of the "neutral" spirit which is affected by the number of times you distill and what methods you use (pot vs. column); and the type of water since well water, tap water, and spring water all impart different flavors.
If you take a Brita filter and filter vodka, it improves the taste. Seriously. You can filter it up to 8 times and notice the successive improvements. It still won't taste like an ultra premium because Brita won't filter out all the fusels and methyls and other nasties that you can remove by distillation, but it WILL improve the purity of the water and some of those contaminants and therefore create a smoother vodka.
Anyway, yeah... it's just science-lab alcohol combined with water to get down to the right proof.
I'd seen those spirit/liqueur kits you can buy and this is basically the same thing so I figured I'd give it a go.
The guy at the Home Brew shop said it was just the same as these kits:
