Distilling the Wash

Once the still is up to temperature, and the distillate has started dripping, make sure you throw away the first 50 mL per 20 L of wash, as this may contain any methanol that is present.

You should expect to collect the equivalent of approx 1L of 40% alcohol per kg of sugar used; the actual % purity will depend on the type of still you are using.

Stop collecting the distillate once you notice them containing some fusels, or if the temperature gets above about 94 oC (it doesn't become "dangerous" or "deadly", just that it tastes foul).

If you collect the distillate in small amounts (say 1/2 L or so), you can segregate the drinkable spirit from that with fusels in; the latter can be added to the next wash, and be collected cleanly then.

"Genuine" whiskey can be made by passing a grain wash through a pot still twice.

The alcohols in the wash begin to vapourise from the wash around specific temperatures. If by themselves they would be ...
  • Acetone 56.5C (134F)
  • Methanol (wood alcohol) 64C (147F)
  • Ethyl acetate 77.1C (171F)
  • Ethanol 78C (172F)
  • 2-Propanol (rubbing alcohol) 82C (180F)
  • 1-Propanol 97C (207F)
  • Water 100C (212F)
  • Butanol 116C (241F)
  • Amyl alcohol 137.8C (280F)
  • Furfural 161C (322F)

Once together, a mixture of several of them will be slightly different however. You no longer get them coming off seperately, but always as a mixture. Fortunately for us though, each of the species will tend to dominate around its boiling point temperature, thus we know whats "mostly" coming off at that point. By tracking the temperature of the vapour, you have a fairly good idea when you're collecting the Ethanol your after (78-82 °C), vs when it is starting to get lean and you're into the higher alcohols.

Note that you may also need to adjust the temperature if you are distilling at altitude - the higher above sea level you are, the lower boiling temperatures become because of the reduced air pressure.

Mark writes Jack adds though ..
    Actually, % of alcohol is a more reliable method of measuring cutoff points than temperature is. Thermometer placement in a still can cause a major difference in how the temp is read. Everyone's still is different- the % is more likely to give predictable results, where the temp can be off by more than 10F either high or low- giving the wrong results when duplication of anothers' run is being tried.
Sometimes with the tails though, even the % isn't accurate enough, with smelly tails sneaking through with little apparent notice. This is when you should also let your nose guide you - collect a few drops on the back of a spoon every so often, and check what they smell like, on a regular basis.

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