Distillation
Distillation for Single Malt Scotch Whisky is carried out in copper pot stills by
“batch“ distillation. Copper is important as it removes highly volatile compounds including sulphur from the distillate. Still design is unique to each distillery but they all have a basic “onion “ shape. Heating of the liquid contained within the still is normally by internal steam coils, external gas or oil burners. Condensing of the alcoholic vapour coming from the still takes place in shell and tube condensers or in some cases, worms.
Condensers are linked to the “Spirit Safe“ where distillate is monitored by use of hydrometers and thermometers prior to being collected in the receivers .
The stillhouse usually also contains vessels known as “ chargers “ where liquid is held prior to being distilled.
Each distillery in Scotland carries out its own unique form of distillation and we will look at the methods carried out at Springbank Distillery. Springbank`s stillhouse contains three stills, one Wash Still, and two Low Wines or Spirit Stills.
The Wash Still is heated with internal steam coils and an external oil fired burner. The two Low Wines Stills are heated by internal steam coils. The wash still and No 2 Low Wine Stills are connected to shell and tube condensers. No. 1 Low Wines Still is connected to a Worm. The two Low Wines Stills also have after coolers.
Springbank Distillery produces three different spirit styles.
Hazelburn : Triple Distilled Lowland style with no peat influence.
Springbank : Two and a half distillations, lightly peated.
Longrow : Double distilled, heavily peated “ Islay Style Whisky “.
Wash
Distillation in The Wash Still is carried out in the same fashion for each of the spirit styles.
Fermented wash is filled into the still up to the level of the man door. The man door and air valve are then closed the steam valves opened and the oil fire lit. The rummager within the still is checked to make sure that it is running. The purpose of the rummager is to slowly stir the wash during distillation in order that the bottom of the still does not become fouled. A certain amount of caramelisation also takes place due to unfermented sugars present in the wash burning on to the copper bottom.
Once the wash within the still begins to boil and produce distillate the application of heat must be controlled in order that wash does not travel up the neck of the still and out through the condenser to the Spirit Safe. The wash still has a sight glass mid way up the neck and froth from the wash should be kept within the confines of this glass.
Distillate, known as Low Wines, flowing from the still is monitored through the spirit safe and collected in the Low Wines Receiver. Once the strength of the distillate has fallen to 1% by volume, indicated by a combination of readings taken from hydrometers and thermometers contained within the spirit safe, the oil fire and flow of steam to the still are turned off, the air valve and man door are opened and the remaining contents of the still known as pot ale are discharged to drain. The cycle is then repeated. A batch of wash takes around six hours to be distilled.
Longrow
Low Wines from the wash distillation which have been collected in the combined Low Wines and Feints receivers is charged to No 1 Low Wines still. The first part of this distillation is returned to the combined receiver and is known as “ Foreshots “. This part of the distillation carries with it a high proportion of highly volatile components which are regarded as impurities that lend themselves to off notes in the new make spirit. The time running foreshots varies from distillery to distillery and is generally 20 - 30 minutes. During this initial part of the distillation water is sometimes added to the distillate in the spirit safe and the strength reduced to 40 - 46% alcohol, this is known as the water test or demisting test. The distillate when mixed with water will initially run “milky“, which is a result of the reaction to long chain fatty acids and their esters remaining in the condenser and inner surfaces of the still from the previous distillation being dissolved in the initial high strength alcohol. Once the distillate runs clear when water is added it can be diverted to the spirit receiver where it is collected as new make spirit. At this point heating of the still contents should be kept to a minimum so that the flow of distillate is slow and the temperature of the distillate collected kept below 20ºC. The flavour compounds required for Longrow production are captured more favourably at a temperature of below 20 degrees Centigrade. This also applies to the other two spirit types produced at Springbank.
The original strength of the distillate collected will be around 70% alcohol. Distillate is usually collected until the strength drops to 58% alcohol at 20ºC at which point the remainder is diverted to the combined receiver. The average strength of Longrow spirit collected in the intermediate spirit receiver (ISR) is 65 - 67% alcohol by volume. Distillation continues until a reading of 1% alcohol remaining in the distillate is achieved at which point the steam is turned off and the remaining contents known as spent lees are discharged to drain. The cycle is then repeated. One distillation cycle takes around 10 hours .
Springbank
Springbank spirit is said to be distilled 2 and a half times and the way that this is achieved is as follows.
Wash is distilled , as with Longrow and Hazelburn production, to produce Low Wines. Low Wines are distilled, as with Hazelburn production, to produce Feints.
A mixture containing 90% Feints and 10% of Low Wines is processed in No 2 Low Wines Still and the middle cut of this distillation is collected as Spirit.
The strength of spirit cut collected from Springbank production will be between 76% and 60% alcohol with the average being 68-70% alcohol in the ISR. One distillation cycle for Springbank is around 13 hours.
Hazelburn
This spirit was first distilled during 1997 and is produced using a “triple Distillation“ process.
During this distillation Low Wines and Feints are collected in separate receivers known as The Low Wines Receiver and The Feints Receiver.
Low Wines from the wash distillation is collected in The Low Wines Receiver and distilled in No 1 Low Wines Still.
The total of the distillate produced is collected as Feints in The Feints Receiver.
No 2 Low Wines Still is then charged with only Feints and Spirit is produced from the “ middle cut “ of this distillation. Foreshots and feints are returned to The Feints Receiver. The strength of spirit from Hazelburn distillation collected will be between 80 - 63 % alcohol with the average strength being 70 - 72% alcohol in the ISR. One distillation cycle for Hazelburn takes around 13 hours.
New Make Spirit
The Spirit collected in The Intermediate Spirit Receiver is transferred to The Spirit Receiver Warehouse Vat where an “account“ of the spirit is taken. An “account“ consists of the vat being dipped and the bulk litres and strength of the spirit ascertained. Spirit is then normally reduced to 63.5% alcohol by volume by the addition of water prior to being filled into casks. The spirit is nosed to ensure that the characteristics associated with each new make spirit is as it should be. Samples are taken for comparison with previous samples to ensure continuing adherence to character.
As always please email any questions and we will try to answer them.
All the very best to you all in the future Stuart Robertson Distilleries Manager
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