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.
gravity distillery - floor by floor
The eco-friendly Gravity Distillery in Mackmyra Whisky Village was completed in 2011, becoming the company’s second full-scale distillery. At the back of the distillery are two large silos each filled with around 40 tonnes of malt – one holding Mackmyra’s smoked malt and one containing unsmoked malt. The first phase of production sees the malt raised to the top of the 35-metre tall distillery. Harnessing the force of gravity between the different phases of production, the ingredients are then transported downwards, undergoing a new phase on each level. During five stages, malted barley, yeast and water are processed into a finished new make spirit.
THE PROCESS - FLOOR BY FLOOR
FLOORS 7 & 6 – CLEANING AND SIEVING
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 (grist) 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
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 silos.
The smoked malt we use we malt ourselves onsite, close to the distillery.
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” (or feints), 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.