Vodka is the most frequently used spirits for homemade liqueurs. The most commonly available is 80 proof. That means that it is 40% alcohol by volume (ABV).
For best results, choose a good quality vodka for your homemade liqueurs. It is not necessary to use an expensive brand, either. I have gotten good results with moderately priced vodka. I have tried many brands – Gilbey’s, Gordon’s, Wolfschmidt, Fleischmann’s – just to name a few brands. These are all moderately priced vodkas. I usually watch the local papers to spot when they go on sale. I would stay away from cheap vodka because of the fact that they contain too many impurities (congeners). These impurities will impart a bitter off-flavor that is impossible to mask with sugar syrup. One such cheap brand I don’t recommend is Popov.
One of our local grocery stores in my neighborhood (Gelson’s) sells a very good store brand of vodka (see photo). It is moderately priced and is of consistently good quality. I don’t have to wait for it to go on sale and I can purchase it at my convenience. Every time I have made a liqueur with this store brand of vodka I have gotten a good result.