* Value corrected to 95% from 82%. (285-ml X .82) / .95 = 246-ml @ 95%
* Value corrected to 95% from 82%. (285-ml X .82) / .95 = 246-ml @ 95%
For all the volumes in the volume column, multiply them by the mapping factor, 1.04, and enter the results in the corresponding volume column of the table for your run. This would enable you to very closely emulate the actual spirit run documented by Figure 3.
Having such a table as a guideline can be very reassuring to a novice distiller just becoming familiar with judging the transition points.
In actual practice, it's not necessary to map up the foreshots if you don't want to. They can stay at 40 to 60 ml for up to a 50% larger run, but make sure that the difference is added to the quantity of heads, so when the transition point to the middle run occurs the same amount of distillate will have passed whether you mapped up the foreshots or not.
Using Figure 2 or 3, depending on whether your run has an adjunct of feints or not, map the volumes of each phase from the bottom table onto your table (copied from Appendix C). You are now ready to begin your spirit run.
Close both ball valves, start running cold water through the heat exchanger, ensure the needle valve is closed, place a 250-ml graduated cylinder under the output, turn on the electric current, and wait for it to boil. With a 750W heater, 20L of corn mash will take about 31 hours to boil. 8L of diluted low wines will take about an hour and a half.
When it comes to boil the still-head thermometer will read about 78oC (172.5°F). Leave the needle valve closed for 20 or 30 minutes to allow the still to equilibrate. If the still is left to equilibrate longer, this is not a problem. When the still has equilibrated, open the needle valve and adjust the flow rate to one drop per second. This can be done by counting the drops for ten seconds. If the number of drops is ten then it's running at one drop per second, and if it's not then the needle valve can be adjusted and the drops counted for ten seconds again and so on until the flow rate is one drop per second.
The spirit-run is now in the foreshots phase and the foreshots are now running into the graduated cylinder at one drop per second. The foreshots can be identified by taking a few drops on a spoon and smelling them. The foreshots should be treated as poisonous and so tasting should not be attempted at this point. Anyway, the solvent-like smell of the foreshots is strong enough to dissuade anyone from tasting them. For the 20L of corn mash, you can collect 40-ml of foreshots and transfer them to a container clearly labeled "Foreshots". They should be discarded, used as gas-line antifreeze, fondue fuel, barbecue starter, paint-brush cleaner, or whatever other use you may have for a highly flammable, volatile, and poisonous solvent.
After the foreshots have been transferred the flow rate can be increased to 2 drops per second (i.e. 20 drops per ten seconds). This is the beginning of the heads phase. The transition from the foreshots to the heads phase is very simple because it's quite arbitrary. After about 40 ml or so of foreshots have passed, the pungent solvent-like smell will have diminished considerably, and since the heads phase serves as a large buffer between the foreshots and the middle-run (i.e. the finished whiskey) it's not necessary to bleed out every trace of foreshots before starting the heads phase.
Using your table, mapped from Figure 2 or 3, you can estimate roughly how much heads to expect before switching to the middle-run. This transition is not so easy to determine. What the operator needs to know is what pure alcohol tastes like. Unlike what most people think, pure alcohol is not harsh or overpowering. Rather, it is very smooth and sweet and can be described as devoid of harshness. After 100-ml or so of heads have passed, collect a few drops on a spoon and smell it and taste it. The novice distillers will think they are tasting pure alcohol, but there will be a detectable harshness and a background of off flavour. The off flavour at this point is due to unwanted esters and aldehydes, which are not poisonous. At this early point while this off flavour is most evident, take a number of drops onto a spoon or into a wineglass and add an equal volume of water. Swirl it around and smell it and taste it. The water will amplify this off flavour and smell so it can be more easily detected. As the heads phase progresses, this off flavour will fade away. Continue to monitor the flavour by diluting with water, and when no trace of this off flavour can be detected, allow another 20 or 30 ml to pass then switch to the middle-run.
Once you are familiar with the subtle off flavour of the heads, you will be able to pick it out very easily, and will only have to dilute the sample to detect it right at the end of the heads phase when the off flavour has all but completely faded away. Be sure to transfer the heads to a container clearly labeled "Corn Feints" and store them for future spirit-runs.
At this point the middle-run has started and the flow rate can be increased to 3 drops per second (i.e. 30 drops per ten seconds). Again, referring to your table, determine roughly how much middle-run to expect before switching to the tails. Although the transition from middle-run to tails is marked by a considerably more obvious flavour change, it is still quite tricky to determine exactly how far you want to let it go before switching.
For the first 75 to 80% of the middle-run the distillate will taste of little more than pure alcohol, but towards the end it will begin to take on a very pleasant flavour that is definitely characteristic of fine whiskey. By sampling a few drops off a spoon every few minutes, you'll notice that this flavour is becoming more and more intense. At first the increasing intensity will taste more and more pleasant, but after a point it will become cloying and overpowering. After a few more minutes it will become very acrid and bitter. The distiller has to decide how far they want to collect this flavour. As a guideline, even the mildest of whiskies do collect a small amount of the cloying and overpowering flavour at the early stage of its presence, and the stronger flavoured whiskies retain progressively more. But don't go too far! The middle-run must be terminated before these acrid and bitter flavours emerge. It defies description, but there is a level of harshness that virtually no experienced distiller goes to, and it creeps up rapidly so when the intense esters are prevailing stay close by and monitor it frequently and be prepared to switch receivers quickly.
When the end of the middle-run is near and the tails are approaching, it's wise to start emptying the receiver into the middle-run container frequently. If you start emptying the receiver every 20 ml or so, then when the acrid and bitter flavours emerge (i.e. the beginning of the tails) then only 20 ml or less will be contaminated with tails.
It's important to note, that when the acrid and bitter flavours do emerge, the entire contents of the receiver at that time must be relegated to tails. If the acrid and bitter flavours were mixed with the middle-run they would spoil the overall flavour of the finished whiskey. This is why it's important to minimize the quantity in the receiver that gets contaminated, so as to avoid losing very much of the desirable flavours leading up to the tails.
It's a good idea for novice distillers to make a point of purposely ending the middle-run on the early side for the first couple of runs, and then go progressively later in subsequent runs as they become more familiar with this transition point.
For the first runs which are ended on the early side, it's important to continue tasting the distillate after the middle-run has been ended to become familiar with the changes in flavour leading up to the acrid and bitter flavours which mark the beginning of the tails.
Spirit-runs that are ended on the early side are smoother and milder, so the progression from the first runs ending early to subsequent runs ending later allows the novice distiller to taste a spectrum of corn whiskey flavour from mild to fuller bodied. This affords an opportunity to systematically determine which they prefer. But remember, if the first run has no adjunct of feints its flavour will be uncharacteristically thin and insipid and taste of raw alcohol.
After the middle-run is completed, it's important that the entire middle-run be placed in a single container and thoroughly mixed. This, when diluted, is the finished corn whiskey.
The remaining distillate is the tails and should be collected until the still-head temperature is about 82oC (179.5oF). The end of the tails phase can also be determined by tasting a few drops on a spoon. When all the acrid and bitter flavours yield to a grainy watery sweet flavour, then switch the still off. The spirit-run is complete. The tails should be transferred to the container labeled "Corn Feints" where they are mixed with the heads, and are collectively known as "feints".
Do not empty the residue out of the boiler until you are sure you are satisfied with the whiskey. If you inadvertently spoil the middle-run by misjudging the transition points between heads and middle-run or between middle-run and tails, you can simply return the heads, middle-run (diluted or not), and tails to the residue in the boiler and redo the entire spirit-run. There is no need to return the foreshots. The subsequent run can be executed without that phase.
The spirit-run can be rerun in this manner several times if required, which is often necessary for a novice distiller becoming familiar with the transition points. This rerun can even be done when a significant portion of the middle-run has been consumed during evaluation. The middle-run cut will just be smaller.
In the tables at Figures 2, 3, and 4, which are data from actual spirit-runs, you will observe that each run records a loss of alcohol around 10-14%. This loss is almost entirely due to alcohol left in the boiler after the still is switched off.
A fractionating still of this design does not need to sustain a loss anywhere near this magnitude. The only reason it occurs is because the distillate that emerges after the stillhead temperature is 82oC (179.5oF) is not usable in subsequent whiskey distillations. In other words, above 82oC (179.5oF) the distillate is not suitable for tails and therefore cannot be mixed with the feints.
If the tails were collected all the way up to a stillhead temperature of 97oC (207oF) the tails would contain almost all the fusel alcohols and heavier compounds. The concern here is that after repeated distillations where the feints are recycled through numerous spirit-runs, the fusel alcohols would literally accumulate from batch to batch, to the extent that the feints would become contaminated with such a high concentration of fusel alcohols that it would pervade into the finished whiskey.
This would not only spoil the flavour of the whiskey, but would predispose the whiskey to causing bad hangovers. A condition normally avoided when making whiskey in a highseparation still.
However, all is not lost. If the operator were to create a fifth phase, namely the "redistill" phase, all the distillate after the tails could be collected in a separate container labeled "Redistill".
The redistill could not be used in the production of whiskey, but once it had accumulated to 10 or 20 litres (2^ - 5 US gallons) it could be redistilled in the spirit still in a manner that rectifies it to pure alcohol. The alcohol could be used to make gin, vodka, or essence-based spirits. It could also be used as grain neutral (i.e. approximately pure alcohol) to be diluted to 40 - 50% alc/vol and blended with whiskey to adjust the intensity of its flavour. This will be discussed later.
When the spirit-run is complete the packing in the column will be flooded with tails. These should be thoroughly washed from the column by pouring generous quantities of boiling water down from the top.
Next, the boiler should be drained and flushed. This can be done by attaching the drain-hose to the bottom ball valve and leading the tube to a floor drain then opening the valve. After the boiler has drained it can be flushed by attaching one end of the flushing-hose to the upper ball valve and the other to a tap with a garden-hose thread. Open the upper ball valve and turn on the tap for a few seconds, let it drain, turn on the tap again, let it drain, and so on until it's flushed.
Flow Rate: In the spirit-run procedures documented in Figures 2 and 3 above, the flow rates were set very low. This was done to slow the rate that the transition points occurred to allow novice distillers an opportunity to familiarize themselves with identifying them and switching the phases. The low flow rate results in the spirit-run operating at a relatively high level of separation. And, this is evident in the alcohol content of the tails (e.g. 82%). In a gooseneck still the tails are typically between 50 and 70% alc/vol. At the relatively higher level of separation the tail congeners are passed across while the water and fusel alcohols are held back. In the end the same spirit is produced but with less water and fusel alcohols. However, there is no question that there are subtle differences between whiskies distilled at differing separation levels.
When you are comfortable with identifying the transition points and switching the phases, you can start running the flow rates considerably faster, even to the point of having the distillate flowing continuously from the still (i.e. not dripping). However, the foreshots should still be taken off at no more than one or two drops per second. The heads should run a little slower than the middle-run and tails, but many distillers run the heads at the same rate.
The way to determine if the flow rates are too fast or can be increased is to monitor the alcohol content of the tails. If the alcohol content of the tails is above 70%, you know that the flow rate can still be increased. If the alcohol content of the tails is getting down to the low 50s, then you're probably running on the fast side and should slow it down a little. These determinations, of course, can only be made from one run to the next.
With small runs like the 20L discussed above, the transition points will come by fast and you will have to pay close attention to avoid misjudging the switches of the phases. However, larger runs will have longer transitions and will be much easier to judge at the higher flow rates. Naturally, higher flow rates and larger runs, particularly in the case of spirit-runs of large volumes of low wines from multiple beer stripping runs, scale nicely to larger operations.
See the table at Figure 4 for actual data from a spirit-run operated at higher flow rates. The flow rates can be run even faster than those of Figure 4 and once you are comfortable with judging the transition points this is well worth experimenting with.
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