Home Distillation of Alcohol (Homemade Alcohol to Drink)

Theory

Summary
When you heat up a mixture of liquids, each of its components will tend to come off seperately. There is a bit of overlap (so it is never pure), but generally we can seperate the ethanol from the water and other impurities present. The more alcohol in the liquid, the more alcohol will be in the vapour, so multiple distillations allow us to increase the strength & purity right up to 96.5%

Distillation Theory

The concept of distillation is really quite simple.
Here's my some-what simplified explaination ....

If you have a mixture of liquids each with a different boiling point, then you heat the mixture, it will heat up untill the lowest boiling point is reached. All the energy then goes into boiling off that particular fraction. Once it has all gone, then the liquid will increase in temperature again, untill the next boiling point is reached, and it then boils off, and so on. Its not actually this concise - in reality you get a varying mixture vapours who's concentrations change, but you get the basic idea.

We start with a mixture (fermented wash) that is mostly water & ethanol, with trace amounts of methanol, propanol, etc. Heat it up and any methanol will come off first, It will then heat up further until mostly ethanol is coming off. After this point you would usually turn it off, but it you let it, the temperature would then rise further, until you start boiling the water & higher fractions off.

Note that you are not changing any part of your original brew - you're not "making" the alcohol, or converting it to something else or nasty. All you are doing is concentrating off the original brew into its various parts. There is no more methanol after you finish than what you started with. What does happen though, is that because most of the methanol comes off at once (first up), it is highly concentrated, and can damage you. You definately don't want to be sampling the first portion of distillate that you collect. But once you have thrown away this part, you have guaranteed that the remaining distillate is safe enough to partake of.

Distillate Strength


You can use the graph below (thanks to Grant D) to relate a liquid's % alcohol and its boiling point. It also shows the % alcohol of the condensed vapour. (The data for the graph (and heaps of other stuff) is on my Calculation page if you're interested in drawing it yourself.)

For example: A liquid of 10% alcohol will boil at 93 degrees (ie the point on the blue line directly above 10 on the Alc by Vol axis). If you head horizontally from the 93 degree point until you hit the red line, then drop down to the alcohol axis, it strikes 55%.

So, for a simple still, a 10% alcohol wash will boil at (initially) 93 degrees and the vapour, once condensed, will contain 55% alcohol by volume. Likewise, redistilling a 40% spirit should result in a brew around 80%.

Alcohol liquid - vapour curves

At % alcohol (liquid) the vapour will be % alcohol


Note that only 96.5% ethanol can be obtained by regular distillation of alcohol & water. Absolute ethanol (100%) is made by distilling with benzene (poisonous) (an azeotropic mixture of benzene, alcohol & water distills at 65C and removes the last few percent of water), by vacuum distillation, or by chemical means (eg using drying agents like molecular seives - which with holes of 3 Angstrom (one Angstrom is one ten billionth of a meter) can seperate water (which has a diameter of 2.5 Angstroms) from ethanol (which has a diameter of 4.5 Angstroms)).

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