When producing spirit from grain, copper in the still plays the important role of removing sulphur compounds from the distillate vapour. Both pot and column stills produce high quality whiskies, but each type makes spirits with different flavour profiles and have their own specific advantages and disadvantages. Whisky produced in column stills: Continuous column stills, like Greenbanks’ Vendome 24-inch continuous system, can be run 24/7. They can also be set up for batch production but are most efficient when set up for continuous double-distillation. Continuous distillation means the still can keep running as long as there is finished ‘beer’ (fermented mash) available to pump to it. Running a continuous column still 24/7 is the best way to keep the column still in equilibrium. Double distillation means that after the first pass (single distillation of 65% ABV in the beer still), ‘low wine’ flows via a condenser into a doubler (continuous pot still) and is distilled again to around 70% ABV in real time. As long as there is finished beer being pumped to the column, it will continuously produce a consistent quality new make from the doubler, which is then ready to be reduced to barrel strength. The continuous column still design is very efficient in stripping out almost all the hearts and separating out all the unwanted alcohols, such as foreshots, heads and tails. Like on a pot still, these production parameters are created and set by the distiller, but only at the beginning of distillation until the vapour temperatures required to achieve consistent quality from the still are reached. As long as the incoming finished beer remains consistent, the still parameters (beer feed, steam rate, pressure, etc.) remain the same, thus producing consistent high-quality distillate. Greenbanks’ 24-inch column still contains 19 perforated plates. Beer is pumped to the still at the 5th plate down from the top and cascades down the stripping plates below to the bottom of the still where it is pumped out to our stillage tank to be delivered to farmers for cattle feed or other agricultural purposes. Boiling points of volatiles (alcohol, congeners, acids, esters, etc) are all different. They separate at different levels within the column, some at the top, middle or bottom and a portion of some always go over with the ethanol vapour. The foreshots and heads are separated by venting them away from the still before they condense with the low wine vapour. This is accomplished by keeping the low wine above a certain temperature before it can be condensed and flow into the doubler for its second distillation. The hearts and tails arrive together in the doubler as a low wine, but the hearts will volatilise at a much lower temperature than the tails, which in the presence of higher alcohol percentages will increase the tails boiling point. The hearts are distilled from the doubler around 87oC producing a ~70% ABV distillate. The tails remain in the doubler liquid and do not come out in the vapour. Column stills are more efficient, and their design makes them more effective at separating the different alcohols and congeners than pot stills. They tend to produce spirit that is both smoother and higher in purity than that which runs of pot stills. Whisky produced in pot stills: Pot still distillation is a ‘batch’ process with slower distillation rates and less overall efficiency. Pot stills are designed such that the distiller ‘charges’ (fills) the still with a single or partial batch of ‘wash’ (fermented wort) then heats it up until the distillation is complete and repeats the process for every batch. The distiller has a lot of manual control over what ends up in the final spirit. They can make the spirit lighter or heavier in congeners (aroma and flavour compounds) based which fraction of the spirit they collect due to the ‘cuts’ they make during distillation. Cuts are where the distiller either empirically or by taste chooses to separate the distillate sequentially into foreshots, heads, hearts and tails as the still is heated through a batch distillation run. Foreshots: the first distillate to be produced from the still. These contain low-boiling volatiles like methanol. The distiller may choose to discard this part of the run. Heads: a mixture of more low-boiling volatiles like aldehydes and amyl alcohols, will start coming over next. Heads are collected and will then be recycled back into the next batch to reclaim some of the good ethanol that is smeared in with the heads vapour. Hearts: the quality ethanol the distiller wants to capture. Hearts are collected in the middle of the distillation run and comprise more than half of the volume of distillate. Tails: come off the still towards the end of distillation when the alcohol is almost fully vapourised and the boiling point of the remaining wash is now much higher than at the beginning. This volatilises (turns into vapour) an increasing concentration of congeners (which are very grainy and astringent) along with alcohol as the distillation progresses toward its end where there is no longer enough alcohol remaining in the pot to justify the energy required to distil it. Tails are collected and mixed with heads to be recycled into the next batch.   The distiller may perform a single, double or triple distillation, but for each distillation the process must start over. The number of casks that can be filled is dependent on the size of the pot still. The consistency of the flavour of pot-distilled whisky depends upon the distiller making consistent cuts and operating the still at consistent temperatures.