Yesterday, when I was running the spirit run for my Green Diamond Whiskey V3, between switching jars and keeping an eye on the flow rate and ABV, I had time to think about how perfect the distillation process is. Stripping runs increases the ABV of the fermented wash by a factor of 3.5 while reducing the volume by a factor of 3.5. After 4 ferments and 4 stripping runs I have just the perfect volume of low wines to run a spirit run. The distillate comes off the spout at 81% ABV and then I let it slowly flow until it is below 20% ABV, and then it's time for the only imperfect process: me making the cuts. I am the only imperfect component in this procedss and all I can do is to screw it up.
This morning I started thinking about how Bourbon is made by the big shots. The wash is continuously fed into a column still, the beer still. The column does what column stills do, it sends up steam from the bottom and fractioning occurs as the wash falls down the column, interacting with the steam going up and the trays inside the column. Compounds are separated. More volatile compounds in the wash turns to vapor and rise, less volatile compounds continue falling down. At some point in the column, the wanted vapors are taken off the column to a condenser. The heavier compounds continues their journey down, the lighter their journey up, both taken off the column at different ends. The result "low wines" at a 55-65% ABV (according to what I have read). In a continuous flow the low wines are sent to the Doubler, for a final distillation.
That is when it occurred to me that I don't know how a Doubler actually works. I know how a Thumper works - it runs off the vapors from the pot still. It's fed continuous as long as the pot still is producing. Then it's emptied. It's batch oriented, not continuous.
A Doubler works on continuous feed of low wines, from the Beer still condenser. The Doubler has its' own heating and distills the low wines from the feed, raising the ABV from 55-65% to 65-80% ABV (there are variations) in the final product. How does that work? I've seen pictures of a Doubler and it looks just like a pot still. It's got a pot and a still head, lyne arm to a product condenser.
Questions:
- How does the Doubler manage to maintain a reasonably even temperature with a continuous inflow of "cool" low wines into a boiler with "boiling" charge? The Thumper is heated by the steam from the Pot Still, but the Doubler heats itself. That sounds complicated.
. How does the Doubler expel the ever increasing stillage?
- How can the distiller prevent overflow in Doubler's boiler, ie more flow going in than vapor going out?
- If vacuum can be a problem in a Pot Still + Thumper, it must be same in Beer still + Doubler?
- Are the cuts of heads and tails all done in the Beer still and no cuts are needed (or possible) in the product coming off the Doubler? That sounds almost as imperfect as me doing the cuts after my spirit run.
- The stillage from the Doubler must contain a lot of alcohol, surely this can't be used as backset in the Sour Mash process? Backset used in fermentation must be coming from the Beer still, right?
- Is the Stillage from the Doubler used as feints somewhere in the process? Where?
I will never be too old for questions.