Copper Pot Whiskey Still

A quickly (and simplified) run down of how we make our craft gin whisky brandy vodka distillery 

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The Distillation Pot

We know that different distilleries operate their stills differently. Some heat fast and then distil slowly, others heat and distil fast. Not only the geometrical shape of a pot still but especially the distillation process affects the taste of the new make spirit.

1. The Principle of Distillation

   
   

The following chart shows the principal setup of a Scottish Malt Whisky distillery with two pot stills. Distilleries with three pot stills and triple distillation are extended by one step correspondingly. Many large distilleries have four, six or more pot stills, which aren't operated in series but in parallel.

The connection of the pot stills can be even more complex, if for example the first distillate from several wash stills or from several production cycles is led into a single spirit still. A ratio of 3:2 or 4:3 of wash stills to spirit stills is also common. You can also triple distil with two pot stills by distilling the final product of the second distillation again in the emptied spirit still.

The chart shows a simple distillery with a wash still and a spirit still.

                                                        Functional Chart of a Pot Still Distillery

The principle of distillation was already known to the ancient Egyptians. Different evaporation points allow for the separation of substances by heating. The substances that evaporate first at low temperatures may be collected and separated from the rest. But the Egyptians used distillation only for producing perfume. Only in the middle ages Celtic monks discovered the production of Whisky - the water of life.

Through alcoholic fermentation the wash (beer) contains approximately 8% to 10% alcohol (ethanol = ethyl alcohol). The alcoholic strength is determined by the yeast used and the duration of the fermentation.

When heating the wash, the substances with a lower boiling point than water evaporate with rising temperatures. The wash can't be heated further than up to the evaporation point of the lowest-boiling substance. All heat energy is absorbed by the substance that changes its aggregate state (from liquid to vaporous), and the liquid can't be heated further. Not until all the substances have evaporated at this specific boiling point can the remaining liquid be heated further.

At standard air pressure (14.69 psi, 1013 hPa) ethanol evaporates at 173,3° F (78.5°C).

2. Wash Still

The wash still has a simple task: It is used for the first distillation of the wash, or in plain English: the beer. The capacity of the stills and the wash backs is usually coordinated. 4000 US. Gal. (15,000 L) to 8000 US. Gal. (30,000 L) are most common.

When hot steam is led into the heating cylinders, the wash still starts to heat the wash. Through the heat movement (convection) inside the still the wash is turned. The wash rises along the warm areas of the cylinders and sinks back along the cooler areas.

After some 30 minutes it gets interesting: Above the heating cylinders the liquid starts to boil, and light substances (predominantly flavour-carrying esters) rise into the air above the liquid level.

The constant supply of gaseous substances leads to a slight overpressure in the still, and the gases rise into the neck of the still. But they don't get far. The wall of the still is still too cold, and the evaporated substances condense at the wall. As time goes by more and more droplets accumulate at the wall and form bigger drops that flow back into the pot.

With rising energy input the whole wash starts to boil at a temperature of approximately 173°F (78°C). The whole still heats up, and the liquid surface becomes turbulent. The high heat input generates mighty bubbles, and the liquid foams and splashes up to the upper part of the neck.

3. The Spirit Still

The second distillation in the smaller spirit stills is carried out much more carefully and slowly. It typically takes approximately 8 hours. Since this takes double as long as the first distillation, often the result of two wash still distillations is collected in the low wines receiver and filled into the spirit still as a whole.

Only few distilleries have such concentration systems because they are expensive. Some distillery operates such a system for all nearby distilleries. In order not to lose the residual heat energy in the pot ale during transport (it still has a temperature of approximately 158°F, 70°C), the wash still is usually drained via a heat exchanger, which returns the pot ale’s heat energy to a future distillation process.

Cooling with Worm Tub Condensers

In the past, the so-called Worm Tubs were used to cool the spirit after distillation in the Pot Still. A Worm Tub is constructed as follows: 

The Lyne arm of the still is simply continued as a conduit and placed in the form of a spiral in a tub filled with cooling water. In this way the Spirit cools down while it is passed on. However, this is a rather complex process that requires a lot of maintenance. For this reason, many distilleries no longer use this type of cooling, but prefer the so-called 'shell and tube condensers'. These modern heat exchangers are much more space-saving and easier to handle. In some distilleries you can still find the traditional worm tubs, for example at some distilleries in the Highlands. Many do not want to do without their worm tubs despite the higher maintenance costs, as this type of cooling can also have a positive effect on the character of the distillery character. Due to the increased copper contact and the temperature control of the water in the tub, the result is a heavier and spicier new make spirit.

4. The Spirit Safe

Since the aggressive foreshots are unwanted in the new make spirit, they are redirected in the spirit safe and not led into the spirit receiver.  Search some to illustrate the function of the spirit safe.

This spirit safe has a long history and a special function. Under British law all pot stills and pipework must be padlocked. So the stillman cannot taste the spirit. Then how is he supposed to know when the foreshots have run through and the desired middle cut has started? 

Yet this is not the only instrument that must be monitored. The density of the liquid depends heavily on its temperature. So the temperature is also measured in order to rectify the density. With density and temperature measured, the stillman can then read the alcohol content off a chart hanging next to the spirit safe.

What happens to the foreshots? They aren't poured away but led back into the low wines receiver. However, the foreshots aren't enriched by this constant reflux. This is where the real magic of distillation happens. The aggressive foreshots are transformed into enjoyable aromatic substances through catalytic reactions with the copper of the spirit still. This is a continuous process, and the quantity of foreshots remains constant in the spirit still.

After the foreshots have reached the low wines receiver, the stillman changes the flow direction in the spirit safe and leads the middle cut into the spirit receiver. If he does it too early the spirit tastes too aggressive. If he does it too late it doesn't matter, since the liquid that is led into the low wine receiver is again used in the next spirit distillation. Thus no alcohol is wasted.

The distillation of the middle cut must be carried out slowly and carefully. If the spirit still is heated too much, the reflux of condensing substances with a higher boiling point at the wall of the still is prevented. Therefore fusel oils can pass the lyne arm and get into the spirit receiver.

While the middle cut is being collected, which takes approximately three hours, the alcohol content falls from 75% to 60%. But even after switching at 60% abv, the distillation continues. The fusel oils (faints) that appear now are led back into the low wines receiver where they are again catalytically transformed by the copper during the next distillation run. The distillation of the faints goes on for a long time and is only halted when a residual alcohol content of 1% is reached so no valuable alcohol is lost with the liquid remaining in the spirit still (called spent lees).

You don't often get the chance to view a low wines receiver from the inside. It contains a milky grey-white mix of alcohol and water on which the thin, oily layer of faints swims.

The distillation process is now complete. The distillation balance for the second distillation in the chart below shows the emerging quantity of new make spirit. In our example of 7925 gal. us. (30.000 L) of wash with 10% abv, the resulting quantity of 734 gal. us. (2.780 litres) of alcohol means a yield of 92.6%.

Why choose HOOLOO Whisky Distilling Equipment, 

①　As an industry-leading supplier of whisky distillation equipment.basically, the raw material HOOLOO Whisky Distillery Equipment made of is high stnadard food grade Stainless Steel 304 and red copper CU to meet request, international standard and worldwide certified to enter different countries, it’s safe to use for alcohol & beverage industry when making whisky liquors. HOOLOO factory has CE Certificates for whiskey distillery equipment as well as our other products such brewery system, fermenter, brite tank,stainless steel tanks etc.

②　Next, HOOLOO products are all manully hammered, welded,polished by each individual workers, workers with good craftmanship in this industry , some are copper welding skillful workers to make sure our copper and stainless steel are perfect to meet customer’s whiskey distillery to Guarantee equipment use and aesthetics. 

Why choose HOOLOO Whisky Distilling Equipment, 

①　As an industry-leading supplier of whisky distillation equipment.basically, the raw material HOOLOO Whisky Distillery Equipment made of is high stnadard food grade Stainless Steel 304 and red copper CU to meet request, international standard and worldwide certified to enter different countries, it’s safe to use for alcohol & beverage industry when making whisky liquors. HOOLOO factory has CE Certificates for whiskey distillery equipment as well as our other products such brewery system, fermenter, brite tank,stainless steel tanks etc.

②　Next, HOOLOO products are all manully hammered, welded,polished by each individual workers, workers with good craftmanship in this industry , some are copper welding skillful workers to make sure our copper and stainless steel are perfect to meet customer’s whiskey distillery to Guarantee equipment use and aesthetics. 

Hangzhou Hooloo Industrial Co.,Ltd machinery, we mainly wholesale customization distillery equipment, fermentation tank, and our other factory manufacture chilling equipment too. 

If you may be interest in getting some distillery or brewery equipment,or chiller to ship together, maybe we can offer price option for you too. 

it's nice to reach out to you again, hope to have the chance to work with you in future on distilling/brewing equipment, Thank you.