Making whisky at the Gravity Distillery
At Mackmyra we strive to make our whisky in as modern, efficient, visitor-friendly and environmentally-friendly a way as possible. To achieve this aim, we decided to build the world’s most climate-smart distillery.
In 2011, our Gravity Distillery was finally ready. Standing 35 metres tall, as the name suggests this building makes use of gravity throughout the whisky-making process. It was designed by the architects TEA whose mission it was to imbue the building with a character that captures the essence of Mackmyra: playfulness, sensuality and qualitative production.
There are three ingredients in whisky: barley, water and yeast. The barley we use comes from Swedish farms and we always look to find the shortest and most environmentally-friendly methods of transport as possible. The water used in the distillery is of medium-hardness and comes from the pebble-bedded river that runs through the estate.
We knew that using gravity would be part of our vision for being climate-smart and the distillery makes use of gravity at each stage of the process. Starting with feeding in the raw ingredients at the top, to collecting the new-make spirit at the bottom, everything falls naturally from one stage in the process to the next. As well as this, all heat generated in production is used to heat our premises.
Right next to the distillery is the boiler that heats the water to 115∞ C. It is fired by bio-pellets and any waste water is returned to the boiler after every production batch to maximise recycling.
Even the straw from the barley is re-used, it is in the construction of the famous Christmas goat in Gävle every year.
Traceability is important to Mackmyra and every bottle can be traced right back to the batch of spirt it contains, so you know exactly in which bottles the spirit ends up. Every batch can be up to 2000 bottles.
When our barley is harvested it is transported to Viking Malt in Halmstad in southwest Sweden, where it is malted.
After malting, the malt itself is delivered into the distillery and brought to the top of the building with the of aid of scoop elevator from where it falls into one of the two hoppers (silos?).
The smoked malt we use we malt ourselves onsite, close to the distillery.
We make our own smoked malt ourselves with smoke from peat and juniper twigs, burnt in the boiler-room. The peat comes from Karinmossen, just outside Gävle, and the juniper twigs we get from an energy company that has the job of clearing power line strips on local heathland.
The whisky-making process
Every floor in the distillery has its own part in the whisky-making process.
Floors 7 and 6 – Cleaning and sieving
Before every batch, 1500 kg malt is opened and sieved, and dirt and stones are removed by blowing air in from underneath. The malt is collected and allowed to fall to Floor 5.
Floor 5 – Roller mill
After sieving, the malt is milled in a roller mill in for different milling grades: fine malt, medium-milled, semi-coarse and coarse. After the stage the milled malt falls to into milled-malt pockets.
Floor 4 – Mash tun
The mash tun is a round vessel with a perforated bottom and arms that are used to stir the mash – the mixture of milled malts and hot water. It is fed by a tube and mixed with hot water, heated by waste heat from the distillery. Mashing extracts the sugars from the grains to become wort, which is then filtered through the grist bed and run off through the perforated bottom of the mash tun. The mash is rinsed with more hot water to extract the maximum amount of sugars.
The temperature of the wort varies from 65 degrees in the start of mashing to 95 degrees at the end. Before it is run into the fermentation room it is cooled to 20 degrees otherwise it would kill the yeast. The wort runs downwards to the fermentation room on Floor 3.
Floor 3 – Fermentation room
We have 12 fermentation tanks, each with a capacity of 9000 litres. From each mash we retain 8000 litres of wort. We use Swedish “kronjäst” yeast, which is normally used for making sweet dough. Fermentation takes four days and produces the wash – a “beer” of about 7% ABV, ready for distillation.
Floor 2 – Distillation
The stills are the traditional onion-shaped pot stills, made by the Forsyths Coppersmiths in Scotland. The stills are fired using bio-fuel (pellets) produced right outside the distillery.
The wash, heated by residual heat runs down into the wash still. During this phase of distillation the wash is circulated with a heat exchanger held at 115 °C so that it boils and the alcohol becomes vapour. The condenser chills the vapour to liquid again (called low wines) and this is collected in the intermediate tank. The boil is stopped when the alcohol content in the distilled vapour goes down to about zero. The spirit is then pumped to the low wines still.
Now finally, it is time to get really involved. The first runnings from distillation are called foreshots (or heads) and consist mostly of highly volatile, unusable alcohol and impurities. This is fed back into the intermediate tank. Then comes “the heart” – the part of the distillation that is used to fill the casks. The heart is collected in a separate tank called “the middle tank”. A valve is used so we can choose in which tank the spirit is collected. After the heart, come “the tails”, low in alcohol and containing unwanted components. These are run back to the intermediate tank.
Using our acute sense of smell and by measuring the alcohol content, we decide when the heart is “cut” from “the head” and when “the tails” are cut from the heart.
The spirit that ends up in the intermediate tank is returned to the low wines still and redistilled with the next batch from the wash still.
The stills are our main consumers of energy. All the residual heat is used to heat other stages in the process and for heating our premises. When the distillation from the low wines still is complete, the new-make spirit is run from the middle tank to the spirit store on Floor 1.
Floor 1 – New-make spirit store
The spirit from the middle tank is run to one of the two storage tanks in the new-make spirit store. Each tank has a capacity of 5000 litres. We mix 4-5 batches before diluting the new-make spirit to 63%. The new-make spirit is then ready for the next stage in its journey – to be filled into casks and matured in one of our maturation warehouses.
If you want to know more about the process or book a guided tour, contact us at email@example.com.