Originally By Tony Ackland
Using a Reflux StillThe alcohol coming off a reflux still will be more distinctive / occur in steps. Rather than a gradual increase in temperature over the coarse of the run, it will get up to certain temperatures (near those listed above for pure fractions), then tend to sit there. The alcohol coming off will be of a fairly steady purity right through, only dropping off late towards the end. You'll probably finish a reflux run at a lower temperature (say 92-94 ° C) than a pot still (say 96 ° C.
For example, my StillSpirits 20L reflux still takes about 1 hour to heat up, then once it gets to about 40 ° C, it then heats up pretty quick to 65-70 ° C. It will then sit there for around 5 minutes, and the first liquid (distillate) starts condensing. After about 5 mL of distillate have collected, the temperature then starts climbing again, up to 80-90 ° C.(Note that these temperatures aren't exactly as in the table above. The water & ethanol form an mixture that boils at a higher temperature - as shown in the graph way back in the Theory section). It will then sit there for the next 2.5-3 hours, and I collect the distillate at the rate of approx 1L/hour. (with my improved reflux still, it now sits steady on 78.2-78.4C for most of this period - eg 95% purity) Slowly towards the end of this period, the temperature slowly starts increasing up towards 90-94 ° C. By this stage, my hydrometer shows me that the alcohol is only about 40%, and I've usually had enough, so I then turn it off. Total time 4 hours. (with the new reflux still, I finish collecting at around 82C, as past there it deteriorates fast towards the rubbish - still 4 hours though)
Likewise, finish distilling at 92-94 ° C, as you've basically got all the easy ethanol, and you're starting to collect the higher ends, heavy in fusel oils (the wet cardboard smell).
Rob has the following advice running a reflux still :
To make it easier to achieve maximum purity I strip the beer first and I remove the first 100 ml to be sure the methanol is out. I stop distilling when the temperature reaches 95 Celsius regardless of the %.
The low wines I have now are approx. 55% and I dilute this to 40% max. for the fractioning distillation. I slowly bring the low wines to the boil and keep the cooling water running at a high rate for maximum reflux at the top of the column. After a while I tune the cooling water until I get a steady drip from the condenser outlet; I keep the boiler at the lowest boiling rate possible.
Every 100 ml I check the % and I put a few ml in a noser (glass) and I add the same amount of water; as soon as I detect a distinct smell of wet cardboard, I know I have to stop collecting the middle cut; the alcohol that comes after this point (not much if the fractioning was going well) is collected, and after a series of distillations I fill the boiler with these faints to collect the remaining ethanol. When checking the alcohol for wet cardboard smell, it is important to dilute the alcohol first to 30-40%, because the undiluted alcohol will not release the smell, and you will notice it too late when you are preparing your wodka, liqueur etc...
You will notice, that the off smell will start to occur as soon as the temperature in the top of the column starts tending to rise above 78,5 celsius or the drip from the outlet starts to diminish and you need to increase the heat to keep the boiler going. Also the % goes down to less than say 92%. Don't waste your vodka now by trying to collect that little bit more !!! After a few runs, you'll get the hang of it; there is nothing better than experience.