The cheerful pillarbox red Porteus mills are familiar sights to many visitors touring Scotch whisky distilleries. The Leeds-based company built their roller mills during the 1960s and they were so durably constructed that they were able to grind for decades through ton after ton of malted barley without ever needing to be replaced. The kit was so good in fact, that Porteus went out of business. These days, technology would have provided the perfect flaw; periodically, the distillery manager would have received an email to say that the Porteus 1.0 software was no longer supported and they would need to upgrade to a new mill to benefit from the latest software. I digress. Typically, as the tour guide shepherds visitors into a mill room, the vibratory, rumbling noises may be so deafening that they have to hurry the party on. If it's impassively dormant, then once everyone has admired the shiny paintwork, there's nothing left to do but shuffle through to the mashtun. You rarely get to poke around inside, or see the clever kit that lies above.
The Isle of Jura Distillery was rebuilt then reopened in 1963, even though there is a history of distillation in Craighouse stretching back over 200 years. Their roller Porteus mill was acquired second-hand from a Scottish & Newcastle brewery. High above the mill's four rollers, Porteus constructed charming wooden cabinets with latched doors to house the malt dresser apparatus; externally, it would not look out of place in your grandmother's living room.
Why is it essential? It's conceivable that detritus from the field can be swept up as the harvest is gathered. The purpose of a malt dresser is to filter out undesirable elements in the malted barley: small stones, residual barley awns, and any leggy rootlets. The kit incorporates a powerful magnet to extract any metallic fragments. Inspecting the slotted cylindrical drum of the dresser at Jura, you can see how it is peppered with sharp stones trapped like flies in a spider's web. The skin of the drum is swept clean by a set of bristling brushes that become thickly coated in flour, resembling the laden branches of a Scots pine tree after a heavy snowfall. This is a vital role as stones could damage, or cause a spark, when they enter the rollers, something to be avoided at all costs in this dry, dusty, and highly combustible environment.
In full flow, a Porteus mill comes alive and it is a wonderful sight to behold: cogs spin, drive belts whirl into action, and a deafening, reverberating thrum fills the room. Millions upon millions of malted grains tumble down into a Bühler weighing scale before dropping into the hungry jaws of the mill's rollers. The first feed roller begins to crush, and by the time the grist exits the fourth roller, the desired ratio of flour, nodules, and husks has been produced.
There may be little remaining kit in our homes or daily working lives that was engineered in the 1960s, but in distilleries across Scotland today, there are beautiful working Porteus malt dresser and mills helping to make the Scotch whisky of tomorrow.