If you're reading this, I assume you are interested in the theoretical transformation of a relatively weak alcoholic mixture into a relatively strong alcoholic mixture. That is, the distillation of whisky.
If you are just interested in creating your own alcoholic drinks from scratch, then I recommend starting with brewing beer (LINK). It's cheaper, easier, and less likely to be illegal in you area.
If you don't know about the early stages of whisky distillation, here is a quick round-up:
Take some grain, and allow it to sprout. Just as it starts to sprout, quickly kill it by drying. It is now a "malted grain". Mix the malted grain with hot water and stir until you get bored - you are dissolving the sugars from the grain into the water. Filter out the solids, and add yeast. Keep the mixture slightly warm (and sealed from the air) until the yeast has turned the sugar into alcohol. You now have a wash that is ready to be distilled. Apparently, the wash has a strength and taste similar to beer, so maybe you would like to start there.
Distillation is the process of separating a mixture of liquids with different boiling points. In this case, we're trying to separate ethanol (alcohol) from water. Pure ethanol boils at 78.4oC, and pure water boils at 100oC, so heating the wash will make the ethanol boil off first.
[Some of my most current projects are now here.]
Step 1: What you need
I will refer to these parts as the vat, column and condenser. You also need a thermometer with a scale that goes to at least +100oC.
Legal point: It is illegal to manufacture spirits in the UK without a distiller's licence which is required under the provisions of section 12 of the Alcoholic Liquor Duties Act 1979 and this includes manufacture for "own/domestic use". For this reason, my images are a mixture of diagrams and stock photos. This goes against the usual practice here, but I kind of want to keep my job, and if I did it for real, images posted here can (in a UK court of law) be used as evidence against me. Before constructing your still, you must check local licensing laws to ensure you are not committing an offence, or obtain a distiller's license.
Since this is more a guide to function than form, you may choose to use different materials to those suggested, such as paying out for all-copper fittings. This is by no means an exhaustive tutorial, so if you are planning to produce quality drinking-spirits on a regular basis (as opposed to something merely flammable), you may even want to invest in a purpose-built still. Just remember (again) that, in the majority of countries where you can read this Instructable, you need to check the legality of distilling alcoholic beverages for personal use.
Step 2: The Vat
Step 3: The Column
If you can increase the surface area within the column, so much the better. Looking in my shed, I see a three-foot length of two-inch diameter tube that would be ideal - it's an old bed-leg. To increase the area inside, I could hammer lots and lots of nails into the pipe, or fill it with steel wool. If I was bothered about rust, I could use a similar copper tube and fill it with broken glass.
The column can be connected to the vat by drilling a suitable-diameter hole in the lid of the pressure-cooker, removing the weight-system. The gap between the column and the lid can be sealed with solder, epoxy, welded, or sealed with a compression-fitting, depending on the size of the column and the materials involved. Do not worry about removing the weights or blocking the safety-valve, as the still is never under pressure unless you do something stupidly wrong. The top of the column needs capping, with a hole in the cap to allow insertion of the thermometer. As with the joint at the bottom, this depends on the exact materials you used - it could be as basic as dropping a tin can over the top and epoxying it in place.
Step 4: The Condenser
This is probably the easiest part to obtain, as coils of small-diameter copper tubing can be purchased from many DIY stores (sometimes called microbore, it is the 8-10mm tubing used to connect up modern central heating systems).
Cut off a convenient length, and insert one end into a hole drilled into the side of the column at the top, preferably level with the bulb or sensor of your thermometer. Seal it in place (epoxy again), and set the other end low down - the alcoholic vapours will cool, condense and trickle downhill into whatever receptacle you have chosen.
Step 5: Operation
As previously mentioned, ethanol boils at 78oC. When the thermometer reaches this point, and remains steady, it means that the vapours surrounding it, and passing down the condenser is mainly alcohol, with some water.
Catch what drips out of the end of the condenser - that is your distilled spirit.
Keep an eye on the temperature. If it starts to rise above 78oC, the bulk of the water is starting to boil, and the vapours you collect will now be making your spirits weaker. You also run the risk of concentrating fusel alcohols in your sprits.
(Fusel alcohols look slightly oily when they drip. If the drips from your still start to look odd, stop the process and save what you have so far.)
How much can you expect to collect?
If you are starting with an alcoholic content of 5% ABV (as many reasonable bitters are), then you will get only around 5% of the volume you put in the vat. That is, one fluid once per pint of wash.
Step 6: Poison!
Methanol (wood alcohol) makes you blind. If you hear about people being blinded by illicit booze, they did not actually distil it, they made some sort of punch with denatured alcohol or antifreeze.
Neglecting to watch the temperature, or heating the wash too quickly, can result in concentration of higher-order forms of alcohol called fusel alcohols or fusel oils (because they look oily). A small amount of fusel alcohols are naturally present in whisky, and can give a spicy, hot or solvent-like flavour. If you get those flavours in a distilled spirit, watch out for a hangover. Be aware: Very high concentrations (usually caused by incompetent distillation) can cause acute illness, including headaches, nausea, vomiting, clinical depression, or coma. Such liquor may be referred to as rotgut.
If in doubt, you can always pour what you have made so far back into the vat and distil it again.
Some people distil the wash twice. They throw away the residue of the first batch, and put the spirits through again. Second distillations should be done more slowly, and greater care taken to watch the temperature, as the temperature of the vapours will change more quickly.
No, they don't. They are open systems, there is nowhere for pressure to build up.
I have not actually distilled alcohol for quite some time, and then I used proper glassware. I used to work in a lab with a license to distil one litre per year, and not for human consumption. Do not rely solely on this Instructable to inform your distilling activities - do some research of your own, check the local licensing laws, and remember to take it easy if you actually dare to drink the resultant liquor.
Take plenty of water with it, and do not even think about driving or operation hazardous machinery, even after a small snifter or two, since you will not know the exact amount of alcohol you have consumed.