As I understand it, a constant temperature of about 173° F is required to distill ethanol out of a fermented mash. How did they achieve this during Prohibition days? Did somebody have to sit and monitor the mash constantly during the entire process and continually adjust the heat source to ensure that the mash did not boil or fall below the temperature needed to vaporize EtOH?
In actual practice, one run is much like the next if you are doing it right.
Once you have a basic procedure, you can fine tune it quite easily. You don’t even need a thermometer to distill moonshine, you can ‘read the bead’.
If you have a reasonable amount of heat input into the distillation system and a decent design such that the mash heats fairly evenly, the temperature will increase in a nonlinear fashion.
The temperature will rise from ambient to the temperature at which the constituent components start to evaporate and then will flatten out until the majority of that component evaporates out.
So, the mash will rise to a temperature of about 170 in a fairly constant manner (some minor constituent components will evaporate sooner, like acetone), then it will stay near 170 for a while during the evaporation of the ethanol, then it will start rising more until it gets to a temperature where the majority of the evaporating liquid is water.
By monitoring what is coming out of the worm, you can taste the “heads” (mainly acetone and methanol), the “heart” (mainly ethanol), and the “tails” (mainly propanol and some other fusel oils) and eventually you will just be producing water.
Generally you want a little bit of the “heads” in your product to capture some of the more volatile flavor compounds.
I think I understand. So what you’re saying is that the mash will reach a steady state at each “plateau,” and the temperature will not rise significantly until all of the volatiles which vaporize at that particular temperature boil off? For example, with appropriate design and operator experience, a distilling apparatus will reach a temperature of about 173° and not rise much further until all of the ethanol is vaporized?
The plateaus are more visible with a fractionating still. A standard still tends to have a more linear response.
But it does happen in steps, the switchover from alcohol vapor to water vapor at the end of the run is pretty sudden.
So by derivation, if you’re monitoring the temperature, does a sudden rise to the boiling point of water tell you that you can stop right there, in the same way that measuring the temperature of a body of water and getting a reading above 32° F tells you that there is no ice in the volume that you are measuring?
Right, it’s because water and ethanol form a binary azeotrope that boils at 78.1 deg C. It will continue to maintain that temperature until the ethanol is gone, then the temperature will increase.
^^^ but with a real moonshine still, you watch the liquid trickling. Alcohol has low surface tension and spreads out.
As the ratio of water to alcohol increases, there’s a switchover point and the liquid runs in little streams instead of sheeting.
There’s still alcohol in the mix at that point, but the run is over.
Or so I’ve read in fictional accounts online.
I have a bonus question too: when people went blind from drinking moonshine, was that because of accidental or deliberate addition of cellulose to the mash? Was it because of the inadvertent, incidental presence of cellulose, or did the moonshiners say to themselves “hmmm…I’d rather feed all this good corn to my family/the hogs. No point in making ‘shine out of it when I can throw this perfectly good sawdust in there instead?”
Mostly that’s leftover propaganda from the first Drug War. Methanol in moonshine is about as common as lye in methamphetamine.
IIRC from news stories, one common cause of blindness, too, was lazy/cheap moonshiners using automobile radiators as condensers for the still, since they seem ideal. The lead solder in the radiator contaminated the brew causing lead poisoning.