The procedure is generally akin to obscuration testing for proofing spirits like whiskey. In this case, we’re using the rotovap to do a lower-temperature distillation by using the vacuum pump to change the vapor pressure inside the distillation, thus we’re avoiding temperature degradation of the retentate. If you don’t have a rotovap, that’s OK; use your lab pot still to perform the same general process. Additionally, you should note that the space in which you perform this procedure must be a general premise area of your DSP, not the bonded area. Because the vermouth is tax-paid, you can’t do this work in the bonded space. We set up our lab as a general premise inside our bonded premise to allow for sampling and testing of other products in our industry. It just so happens to also work for this process. Using the presets from the rotovap, we chose the ethanol setting which will set the rotation of the retentate flask to 100 RPM, the vacuum pressure to 175 mBar and the hot water bath temp to 60C. This rotovap can monitor cooling water return
temperature and will continue to run until the distillation is complete, which is determined by the deltaT of the cooling water return vs the cooling water supply. We filled the retentate flask with 500 mL of 16 percent ABV vermouth. We attached an empty collector flask, started the cooling water, and started the distillation. From a 500 mL sample at 16 percent, the math suggests that we’ll recover about 80mL of PLA (pure liquid alcohol). However, since azeotropes are involved and we’ll be distilling a bunch of water over in the distillation, we’ll end up with a 60-70 percent ABV distillate in the collector flask. The product left in the retentate flask is what we’ve been shooting for: non-alcoholic vermouth, ready for the tasting room. Now…we can make a classic cocktail and do it within the rules. Cheers!
John McKee is co-owner of Headframe Spirits and he uses upside down distillation in just about everything he does…which probably explains a lot to those who know him.
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