05. ABV and Flow Management - larry-athey/rpi-smart-still GitHub Wiki

The first thing to keep in mind about ABV management is that you are dealing with a value that always wants to creep downward. For example, in a plain old pot still with no reflux capabilities (no dephlegmator, bubble plates, etc) your distillate in your parrot will usually be reading 140 proof (70%) when it starts overflowing, and slowly decrease in value. Columns with a helmet or bubble plates can usually start out at 160 proof (80%), but also decrease in value over time.

When aging whiskey in a barrel, you generally want it to be between 110 proof (55%) and 120 proof (60%) or you will start pulling unwanted flavors out of the wood. Even in Kentucky, laws regarding bourbon say that it has to be distilled at 160 proof or less and go into the barrel at 120 proof or less.

So, keeping these two facts in mind, a person can target barrel strength whiskey by using ABV management and a target minimum of 120 proof (60%). Once the hydrometer reads below 60%, the RPi Smart Still controller will start to decrease the temperature range of the dephlegmator by 0.5C every 15 minutes until the ABV comes back up to 120 proof. This is a actually reflux mode program, but with a high temperature range on the dephlegmator.

You can't do anything about the high starting ABV because you would need to inject water to bring it down. What you could do to help offset this would be to start with a lower target proof so that "smearing" will help level it out to 120 proof. This is one of those things where you will need to do some test runs with your still in order to find the values that work for you. Always keep a supply of 90% white lightning on hand that you can redistill with water for test runs.

When using a pot still mode program, the minimum ABV will be used to stop the run in order to eliminate or reduce tails in the distillate. For example, a person can set a minimum ABV of 70 proof (35%) and let the still automatically shut down and cool off a bit. Then switch to a maximum reflux mode program and finish stripping out all of the remaining ethanol at 90% or greater. What comes out at this point will have zero flavor because there's no water vapor in it.

You can also shut down a run by using the flow management feature, this works the same way in both reflux and pot still mode programs. During your test runs, keep an eye on the Hydrometer Flow Rate in the user interface above the ABV/Proof display. Make some notes on this value so you can get a feel for how your flow rate registers. Keep in mind that 1/2 liter per hour will register 100%. You can then choose a minimum flow rate to shut down your still.

If you are using ABV management and the LIDAR hydrometer reader, you should wait to drop your hydrometer until after the parrot begins to overflow. This will prevent a false start caused by the reflector being too close to the LIDAR sensor. The system waits for the hydrometer to read more than 20% before it begins tracking things. If the reflector is too close to the sensor, it can possibly produce a false 95% or greater reading and trigger a false start.

NOTE 1: Never redistill anything greater than 40% ABV or you could make things go BOOM! If you are using 90% white lightning to perform test runs, you should always water it down so that your still is charged equal to any wash that you would fill it with. Your test runs should be as close as possible to the real-world situation that you are developing your programs for.

NOTE 2: Redistillation is a common practice in the distilled spirits industry, most any vodka will say that it's been distilled a number of times to produce a more pure taste. Also, there would be no such thing as gin if it wasn't for redistillation. "Cyrus Mason" and "Windsong", the Still'n The Clear charlatans, booted me from their MeWe group for discussing this topic because I was somehow putting their users in danger. For the sake of your own knowledge, avoid any of their groups on any social media platform. They tend to use the group name "Moonshine For Beginners" and like to feed people limited information or downright false information. I suggest sticking with more popular and better established groups and YouTube channels.