Dad’s Hat process
1. To create his mash bill—the ingredients that go into the initial fermentation (80 percent rye, 15 percent malted barley, 5 percent malted rye)—Mihalich mills 2,000 pounds of rye and 500 pounds of malted grains into flour. He mixes in water to yield 1,000 gallons of mash.
2. The mash is cooked down, converting grain starch into sugar, then cooled and mixed with three pounds of yeast. Dad’s Hat starts with fresh yeast, instead of yeast fermented from a previous distillation, to create sweet mash. This produces a higher pH for a wider range of flavor. The mixture is pumped into a fermenter and held within a constant range of temperatures to prolong fermentation for a smoother, more complex spirit.
3. The fermented mash is pumped into a pot still for a first round of distillation, called stripping. This is to separate the alcohol and congeners (at this point, called low wines) from the mash. The low wines are then moved back to the pot still. An attached side column allows Mihalich to control the process, making “cuts” where he determines the head (early waste), hearts (the booze), and tails (the unpleasant finish).
4. The rye comes off the still at 155 to 160 proof. It is diluted with water to 120 proof, then transferred to 15-gallon barrels. The smaller barrels provide more surface contact between the liquid and the wood (torched to a No. 4 char). This develops a deeper flavor profile and naturally produces the deeply amber, almost flame color of real rye.
5. The big differentiator for Dad’s Hat comes at the bottling, which isn’t done on a per-batch basis. Instead, barrels are emptied into a 1,600-gallon tank that is never allowed to drop below one-third full. The new spirits are blended with the old and then bottled, leaving one third of the tank for the next batch. This way, each bottling is a mixture of different ages, always with a distinctive core flavor. The process is similar to a Spanish method of maturing sherry called solera.
Process description from March 2016 Popular Mechanics.