Distill it.

There are basically two steps to making this. First is heat up aka boil the grains or potatoes the for the separation of the solids from the starchy goodness. Then yeast is used to ferment the resultant liquid. That make take up two a few weeks. A special adapter is used to the the carbon dioxide leave the container without letting in oxygen in.

After the fermentation, second is the purification distillation of the alcohol from the water. Alcohol boils at 173 degrees Fahrenheit where water does not boil till 212 degrees Fahrenheit. The vapor is then quickly chilled for storage.  In the real world, this may be done several times to make sure the result is pure enough.

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Alternative parts:


Ultra simple distiller:

Fermentation tank: bottle with balloon that has a few pinholes.