Unlike whiskey or gin, which employ impurities for flavor and color, vodka does not require any additives or aging to qualify as a spirit. However, the difference between good and bad vodkas is based on how well or poorly impurities are filtered out of the base ethyl alcohol-a process known as distillation. "Bad" vodkas, which often have a metallic, robot-corpse taste and battery acid burn, fail to filter the alcohol well. Good vodkas, which typically have a pristine, distilled-water-like taste, do a better job of it.
Iowa State University professor Johannes Van Leeuwen has invented a new distillation process that produces a clearer vodka, which has zero measurable impurities. His company, OZ Spirits, released it in local liquor stores about a month ago under the name ingenioz. Made from corn sourced in Iowa, the vodka's makers claim that it is of higher quality and less likely to cause hangovers than Smirnoff, Absolut or Grey Goose. The reason, they say, is that it has fewer congeners, which are the byproducts of the fermentation process that contribute to hangover symptoms.
The ingenioz makers have a number of tests to prove that their product is the purest on the market, and that other methods (multiple distillation, filtration and charcoal treatment) do not improve the level of impurities as much as their own. They also have test results showing that the raw fermenting material and the country of origin do not play a significant role in impurity levels.