Talking stills

Talking stills

In the first of two articles on stills, Ian Wisniewskilooks at the role of the wash still,and what happens\rduring the first distillation process

Production | 19 Jun 2008 | Issue 72 | By Ian Wisniewski

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It’s easy to dismiss the wash still as entirely pragmatic, like a manual labourer that repeats a basic task, while the spirit still tends to be hailed as an artist performing a creative role.But the only reason why the spirit still can yield such a refined result is because of everything the wash still achieves.So, while each type of still has its own individual mission statement, they are both equally important.“We capture the key components in the first distillation, of which the majority of flavour congeners are created during fermentation, and although you can’t detect some aromas in the low wines they are there,”says Highland Park’s Russell Anderson.“The second distillation concentrates the alcohols and releases some of those characteristics, allowing them to come through organoleptically, while also creating additional characteristics.” Pre-heating the wash prior to distillation is an established practice, saving energy and therefore costs.But pre-heating is also a great example of efficiency, as pot ale (ie. the residue from the previous distillation) is conducted through a heat exchanger after leaving the still, while hot.This transfers heat from the pot ale to the wash, which passes through the heat exchanger on its way to the still.Pre-heating raises the temperature of the wash from around 25-30 degrees centigrade (ie. the temperature following fermentation), up to around 60 – 65 degrees centigrade.This means significantly less energy is required to heat the wash to boiling point.Apart from saving energy, another benefit of pre-heating is saving time.And with production schedules at various distilleries at full stretch, this can be a vital advantage.“We’re not only saving fuel, it’s also a turn-around measure, as you’re having less down time waiting to boil up the still.When distilleries are very busy it’s important not to have down time, and have a quicker turn-around from one distillation to the next.But the final judgement with cost savings and turn-around measures is always spirit quality. If we find that pre-heating too much has a detrimental effect we would stop.So, it’s not a question of saving energy or time at all costs,”says Russell Anderson.Turning up the heat and bringing the wash to the boil as efficiently as possible is standard practise, with the heat being reduced once the surface of the wash begins to foam up. In fact, managing the foam is a crucial issue,as mismanagement entails a risk of undistilled matter carrying over through the condenser, which would compromise the quality and character of the low wines, so it’s the stillman’s job to ensure this doesn’t happen.“There’s no computerisation at Glenfarclas, everything is done manually and the stillman makes all the decisions,”says Ian McWilliam of Glenfarclas.Making decisions is helped by the fact that wash stills have windows, which provide the stillman with a significant view.“Two windows is standard on a wash still, and you reduce the heat when the foam reaches the first window.The second window enables you to see that there’s no foam at that height so that you can perhaps reduce the heat even more and avoid the carry over of wash.The distance between the first and second window varies among distilleries, but how much higher it is depends on the size and shape of the still,”says Kenny Gray of Oban.“We only use heat to control the foam,which is just the surface layer, and settles very quickly once the heat is reduced.The foam settles more quickly in winter than summer due to the ambient air temperature.Once the foam has broken you can increase the heat without recreating too much foam,”adds Kenny Gray.A related factor is that a shorter fermentation period can mean a more‘active’wash, in the sense that it froths more readily as it comes to the boil, and so requires greater management.Indirect heat (ie. steam conducted through pipes within the still), is the usual method of heating stills.Meanwhile, isolated instances of direct fired stills remain, with the exterior of the still heated for example by a gas flame.“Glenfiddich uses gas, the base plate is made of extra thick copper compared to the base of a still using a steam coil, the heat is spread evenly and there aren’t any hot spots, this has never been an issue,”says John Ross of Wm Grant.Using direct fired stills also means utilising rummagers.As the wash includes certain solids, such as yeast residue, a rummager is equipped to deal with the potential risk of caramelisation within the still.Here’s how it works.“There’s a shaft in the centre of the still with three arms, from which copper chains hang down the sides and base of the still, with the chains comprising links that are each two and a half centimeters in diameter.The chains go round the still very slowly, touching the base and side of the still, like a carpet covering an area of around 30 cms.The rummager is on from the beginning of the week until the end, whether we’re distilling or not, as even though the gas fire might be off there is still a lot of residual heat.There’s a fail safe mechanism, if the rummager isn’t running then the gas fire won’t start,”says Ian McWilliam.When using steam heating there’s the option of having what are known as pans or kettles.These either resemble cylinders, with several rising vertically from a ring situated at the base of the still, or a series of rectangular ‘radiator’ shapes.Whichever option is utilised it’s vital they are kept clean, as any solids forming on the surface will compromise heat transfer, and therefore efficiency.“We have steam pans in the wash stills and as pans can foul up, we have a‘cleaning in place system’, an automatic internal system,”says John Campbell of Laphroaig.So,once the heat is on,what actually happens during distillation? In terms of characteristics the lighter, fruitier notes come over first, which can result in the stillhouse being filled with an intense aroma of apples and pears; followed by richer, heavier notes.But that’s not the only way of looking at it.“The vapour stream is initially far richer in alcohol, and then the only way is down in terms of alcoholic strength.Meanwhile, the temperature increases gradually.The lowest vapour temperature is at the start when you have the highest alcoholic strength, then there’s a gradual progression to 100 degrees centigrade,”says John Ross.The difference between using shell and tube condensers, compared to worms, is that condensers promote more copper contact with the vapours, and so a relatively lighter spirit than worms.But how the worms are run is also an important factor.“Copper contact is maximised by regulating the flow of cold water through the wormtub, which is three metres deep. Ours are huge worms,about 120 metres, which are also not in the usual configuration, ours are like a huge paper clip rather than decreasing circles.Vapours take longer to condense and so have a longer time in contact with copper,”says Kenny Gray.The first distillation can last from around five hours to seven and a half hours,depending on the distillery, which results in low wines with a strength of around 20-25% abv.This means that approximately one third of the wash becomes low wines, with two thirds becoming pot ale.Quantifying the difference between the wash and low wines, and establishing exactly what the first distillation achieves, is not that easy.Whereas new make spirit is continually analysed by nosing panels, the wash and low wines aren’t analysed to the same extent.One consideration when producing a peated malt is how the level, and range, of phenolic compounds change as a result of the first distillation.“The slower you distill and the larger the surface area, the more reflux you get, and generally the lighter the spirit character.Changing the rate of distillation can also affect the range of phenolic characteristics coming over at peated distilleries,”says Kenny Gray.John Campbell adds, ”Some phenolic characteristics can be concentrated by distilling, but not all, and the rate of distillation is equally as important as the temperature of the distillate produced, so you need to be consistent. If you distill very fast you’ll push more of the heavy characteristics and oils through.“At Laphroaig we distill very slowly so we get the lighter bodied flavour profiles coming through.Some of the phenolic character of the malt will be lost during the distillation process, and you will loose more in the wash still than the spirit still, our pot ale is still very peaty.”
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