If you would feel better using 100 proof alcohol just add two 200 ml bottles of Everclear to the 1.75 liter bottle of 80 proof Vodka and you're there. That's the small glass bottles that are available most places. That may not be exact but without weighing it down to the gram or smaller it is definitely close enough. It takes about 25% alcohol to preserve the tincture and unless you are using fresh herbs that will be enough. The 40--60 mixture of alcohol and distilled water in the 80 proof is sufficient to extract the properties of most herbs except things like Chaparral, Lobelia and a few others.