Boiling point of Alcohol
The principle of the distilling process is to heat a liquid to its boiling point and let it turn into vapour (steam) then turn it back to a liquid. Boiling point of a liquid is the temperature where it begins to boil e.g. 100 degrees Centigrade for water, 78.5 degrees Centigrade for ethanol (alcohol).
The process can be seen if you boil a kettle and the steam hits cold tiles or glass the steam condenses back into a liquid. In a still the vapour is transported through tubes and collected in a separate vessel.
This process of vaporizing then condensing a liquid has the great advantage of leaving the impurities in the boiling liquid, the vapour is pure. For example if you boil salt water the steam you condense has no salt in it.
If you boil a mixture of two or more liquids such as in a refinery the one with the lowest boiling point will crack (boil) of first, so you can see that the liquids can be separated by adjusting your apparatus to the liquid with the lowest boiling point then cracking that of first then adjusting the temperature to the boiling point of the next liquid etc.
Ethanol and Water
The mixture we are interested is ethanol and water so if we heat it to 78.5 degrees centigrade the ethanol will start boil and turn into a vapour to be collected in a separate vessel leaving the contaminants and impurities in the original vessel.
Boilers and Condensers
The equipment we use to do this is called a still consisting of two parts, a boiler and a condenser. With a quite bit of handyman skill you can make a still (there are construction drawings on the internet) but the easiest thing to do is buy one. The two I would recommend are the Still Spirits Turbo 500 or The Pure Distilling Home Spirit Maker both these stills are extremely efficient and amazingly cheap for the advanced technology you get for your money.
High quality Alcohol
In these stills the boiler boils the mixture in excess of 100 degrees centigrade and the condenser reduces the vapour to 78.5 degrees centigrade to produce very high quality alcohol.