Distillation is more an art than a science, since you mostly depend on your senses, and only seldom measurements will help you. Therefore some practice and experience is needed, but this article will help you to get through the first attempths.
The aim of distillation is to separate different components of a substance by heating and condensig the vapors. In case of distilling the mash, our target is to extract acohol and different aroma components.
The distillation is based on the fact that different materials boil at different temperatures. So - in theory at least - if we heat a substrate evenly, the different compnents will start to evaporate one after the other. Then, if we condensate the vapors, we can separate the different compnents.
Of course, in reality it is not so simple. Once, the different liquid components tend to combine, therefore the real boiling points will differ from the theoretical ones. On the other hand, it is not too easy to heat the substance evenly. E.g. it can happen that next to the wall of the distiller the liquid's temperature is some degrees warmer than in the middle. It will result in different materials evaporating from the warmer liquids next to the wall than from the middle. For example the valuable ethanol will evaporate at the same time as the harmful methanol - making it impossible to separate them.
In practice we don't want to separate all the volatile components of the mash, but we categorize them into three groups. The heads are the part of the distillate that will flow first from the condenser. The heads includes harmful compnents, therefore it should be discarded. The next group is the hearts, which is the part of the distillate that fits human consumption, including ethanol and aroma components. After the hearts come the tails, which includes different types of alcohols that don't fit to human consumption. The tails aren't toxic, but their taste and smell are quite unpleasant, and for this should be separated from the hearts.
We start the distillation process by separating the volatile components from the solid materials. At the first distillation it is not necessary to separate and discard anything, the only thing we have to take care of is to avoid the burning or caramelising of the mash.
The best solution is to use double walled (also called bain marie) distillers. If you have such kind of a dilstiller, you will never burn your mash.
Another known method is to use a built in mixer, which make it possible to blend the mash inside the closed pot.
But the cheapest, and so the most popular distillers are those with a single wall and without any mixer (like Hazai types). If you have one of these types, you need to pay some attention, but you can still avoid burning the mash.
First of all, especially for those distillers under the volume of 50 liters, it is important to use a sphere-shaped pot. In these kinds of pots the mash is forced to move continously, making it harder to burn. As an additional protection it is recommended to purchase a copper sieve tray. Placing this accessory into the pot, it will filter the mash so that only the liquid compnents will flow through, therefore protecting solid components from the direct heat.
But the final protection is moderate heating - so a controllable heating is mandatory. It requires some experience to know how much heat you can use for different types of mashes. After some time you will find the appropriate settings to ensure acceptable distillation time without the risk of burning the material.
Never forget: distillation is not for impatient people. Don't start distillation if you cannot afford the time for it!
After the first distillation you will receive an opaque liquid with bad taste and smell, which doesn't fit for human consumption. A second distillation is needed to separate the valuable components from the useless, or even harmful ones.
As already mentioned, if we start heating the liquid, the first drops arriving from the condenser will be the heads. If you have a built in thermometer, you can expect the first drops to arrive after 65 degrees. The heads are easy to identify by it's opaque color and its diluent smell. This part is toxic, so must be separated and discarded. Fortunately it's quantity is not nore than 1-2% of the whole distillate.
During the second distillation, slow and even heating is even more important to ensure that the different components will arrive separately one after the other. The heatng performance is correct if the distillate drops slowly. If it drops quickly, or flows, decrease the heating perfromance.
As diluent and solvent smells are replaced by the smell of pure alcohol and the tipical smell of the raw material (fruits, grains, etc.), you will know that the heads part is over and hearts are starting to arrive. Hearts should be collected separately from the heads.
Hearts are the valuable part of the distillate that we intend to consume. It has a strong alcoholic smell, it is clear and transparent like water, and shows the odor and flavour of the original material. It's quantity is around 1/3 of the whole amount.
During the distillation of the hearts the slow dropping of the distillate should be maintained through the proper control of the heat performance. In case of having a built in thermometer, you will notice a small increase of the temperature within the dome. It means that ethanol is about to give out, and more and more water starts to evaporate. The alcohol content of the distillate will start to decrease slowly. Later besides water some other components of the mash will also start to evaporate, which belong to the third part, the tails.
Tails are not toxic, but they have unpleasant smells and tastes, therefore we should take care not to let them mix with the hearts. The separation of the hearts and the tails could be done by measurements, if we measure the alcohol content of the distillate time by time. The exact point of the separation is not exactly determined, it is much a question of personal taste of the distiller, but usually between some 45 and 55 percent you should finish collecting the hearts.s kérdése.
Another well known method is collect the hearts in more smaller numbered bottles. When the tipical sour smells of the tails can be felt, we stop collecting the hearts, amd start to examine the bottles in converse order. At first we smell (maybe taste) the content of the last battle, and decide wether it should mixed with the hearts or not. If you feel the characteristic smells of the tails, then you discard the content of this bottle (or handle as described below), and examine the next bottle. Continue until you find the latest bottle that features the pleasant falvours and aromas of the hearts. The remaining bottles can be poured together and bottled for the final handling described below.
As the tails are about to flow from the cooler, the distillation process could be stopped, but some distillers collect the tails for a lalter re-distillation. It is a common practice of home distillers to distill the whole amount of mash (or wine) multiple times, so a smaller disitller is enough. This case the collected tails of the several distillation can fill the pot again, and worth re-distilling. The method of the re-distillation is the same as the second distillation, and the result is a smaller amount, less tasteful, but still enjoyable distillate.
Finishing the destillation doesn't mean that the distillate is ready for consumption. The distillate should be bottled and left to "rest" for at least three months. During this resting period the copper ions, oxygen and some alcohols will react, creating important aroma components.
It means - once - that copper is the only material of a distiller that makes preparation of high quality distillate possible. Also, oxygen is needed for the distillate, therefore you should air it time by time.
After around three months, these chemical reactions will be finished, and your distillate will perform a softer, and much more harmonic flavour.