Distillation and The Still.
The first stills came to be known in Europe as Alembic from the Greek ‘Ambix’ (small vase). Often made from copper or ceramic and mounted on a recessed lamp with a metal or ceramic cap for the drops of vapour to condense. From here the condensed liquid would travel down a grooved channel to a flask.
Most often distilled from a wine base the pure liquid drawn from this basic process were called spiritus vini- wine spirit and later ‘Aqua Vitae’- water of life. The spirit produced would be similar in concept to Italian Grappa but the unregulated heat would suggest a flavour more closely related to rice wine or white wine vinegar.
‘[Spirits] strengthen the body and enlarges the life.’
Arnaud de Villeneuve
The Alembic still is generally thought to be the forerunner of all industrial distillation techniques. The traditional pot still, which remains popular in the production of Caribbean rum is a only slightly refined version of the Greek original.
In the religious darkness of medieval Europe distillation as an alchemical process was only practised behind closed doors as these early scientists were thought to be dangerous druids and heretics. Later the Holy Roman Inquisition would put alchemists to death believing them to be challenging the natural order emplaced by their god. In these hysterical and brutal times the world lost many great many artists, scientists and philosophers. Had the zealous attentions of the Pope’s minions been applied to the support of these people the world would doubtless be a richer place today.
Early in the 15th Century Hieronimus Brunschwygk (1450- 1512) printed in Latin his book Liber de arte destillandi- the free art of distillation to describe the use of distillation to create medicines and balsms for aid. This work helped to remove the dark clouds from around the ‘arcane’ process of distillation, Allowing Giovanni Michele Savonarola (1385- 1468) to publically describe the method of obtaining spirits through distillation for the purpose of consumption.
For centuries the process for the distillation of alcohol changed little with the only real alterations being the additions of flavour and sugar to create liqueurs from the harsh ‘Aqua Vitae’. The process of distillation became so wide spread that by the mid 18th Century London in particular was awash with cheap spirits particularly gin. Gin was easily produced and pungently flavoured. Around the time of Hogarth’s now infamous Gin lane one in five houses in London was thought to contain an illegal ‘gin mill’. (For further information on this period see the excellent dissertation ‘The Socio- Economic Effects of Gin on 18th Century London (2006)by W. Boucher- Giles(!))
Thought ancient history, puritanical dark ages and turbulent modern history distillation has advanced sufficiently that there are now varying types of still and distillation techniques for the production of thousands of varieties of alcohol.
The two most popular modern distillation techniques use either the pot still or the continuous or Coffey Still.
The Pot Still
The pot still as mentioned above is the simpler of the two methods relying on the evaporation of alcohol at boiling point 78.4° C and water at 100 °C. The process simply involves heating a liquid that already contains alcohol (wine) to 78.4°C where the alcohol evaporates. This evaporated alcohol is then collected in a glass tube to condense and reform as liquid to be collect in a separate container as a pure alcohol- just as Zosime noted of the ancient Egyptians.
Clearly the process has become more scientific in recent generations. To cool the alcohol more quickly a leibig condenser is used to replace the traditional glass tube. A Liebig condenser passes the steam / liquid through a coiled glass tube surrounded by running water to rapidly condense the alcohol. The lower boiling point of alcohol as allowed it to recombine in the condenser as a purer alcohol than was contained in the base liquid as all of the impurities have been left in the first chamber.
Pot stills come in two varieties a ‘round head’ and a ‘flat head,’ the type of still can effect the flavour of the spirit greatly as during the fermentation process as the sugar becomes alcohol certain chemical reactions take place as well. These reactions produce the ‘impurities’ such as congeners, acids and esters that give an alcohol its aroma, flavour and texture. As with the tannins in red wine the more ‘impurities’ in the spirit the heavy the flavours, t he fewer the lighter. A round head still allows more of these compounds to filter into the condenser and so often produces a heavier flavour in the finished product. As such these still are favoured in the production of rum and Cognac.
The flat head still favoured in the production of vodka amongst other things does not allow for much impurity to pass into the condenser as when the vapour hits the flat roof of the still the heavier compound particles of the impurities fall back down into the mix and the lighter alcohol moves into the condenser. This should show you why the concept of ’10 times distilled’ vodkas is pointless sales gimmickry as the extra distillations make little difference to the purity of the product and serves only to leech out still more of the flavour.
The Continuous or Coffey Still
Named for the Irishman Anneas Coffey this method of distillation was actually developed by Scotsman Robert Stein although perfected by his Irish counterpart.
As the name suggest the continuous still allows for a near conveyor method of distillation producing a purer spirit in a faster time than the pot still.
The key difference is the still itself as in continuous stills there are two or more ‘columns’ that are linked in cyclical series allowing a continuous flow of ‘wash’ to move between the two column stills and continually be evaporated and condensed to gain the maximum yield from the base liquid.
1. First the wash enters the first column ‘rectifier’ or ‘wash still’ and passes down the column heated as it passes through.
2. The heated liquid now lighter passes up a pipe to enter the second column the ‘analyser’ at the top and filters down the column.
3. Steam is introduced at the bottom of the analyser to rise up through the condensing wash, turning it back into vapour.
4. The vapour rises back up the column back into the base of the rectifier, where it travels back up the column being cooled by the pipe containing the newly introduced cold wash, splitting the vapour into alcohol and water.
5. When the alcohol reaches around 90- 95% ABV it splits from the water and perforated metal plates inside the rectifier collect the spirit at the sides of the column as the steam passing up through the holes stops the alcohol falling back down but instead vaporises the water again thus separating the two parts.
6. Wash that is not converted into spirit is then fed back into the rectifier cold to begin the process again.
The advantage of the continuous still is the ability to distil spirit at high strength and purity, around 96.5%. The down side is that this process also produces a near tasteless liquid and so is predominantly used in the production of spirits that take their flavour, aroma and texture from the aging process and certain additives, the best example of this being the differences in taste between the types of Scotch Whisky.
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