What is a spirit safe?

A spirit safe is a locked cabinet of copper and glass, placed behind the still, through which the fresh distillate runs before it disappears into a tank. Through the panes the distiller sees the liquid, but cannot get at it: the cabinet is padlocked.

In the cabinet hangs a hydrometer, an alcohol meter that sits in the stream. Together with the temperature, the distiller reads from it how strong the distillate is at that moment. With taps on the outside he directs the stream to one tank or the other, without opening the cabinet.

The spirit safe is locked because excise duty was levied on the quantity of alcohol that came out of the still, and nobody was allowed to get at that liquid. Anyone who drew off a jug along the way paid no tax on it.

The Excise Act of 1823 changed the British excise rules and obliged every distillery to house a permanent excise officer. That officer kept the keys to the warehouse and to the spirit safe. The cabinet thus became the official measuring point on which the assessment was based.

The distiller reads the alcohol strength behind the glass and switches the flow with the taps as soon as the foreshots give way to the heart of the run. A distillation falls into three parts: foreshots, heart (middle cut) and feints.

In practice, the flow goes to the spirit receiver at about 75 percent alcohol, and at roughly 70 to 60 percent goes back to the low wines. Foreshots and feints go back into the still. Only the heart becomes whisky. Every distillery sets those cut points differently, according to the flavour profile it wants.

Since 1983 the British tax authority no longer keeps a permanent official at the distillery; the management holds the key and itself accounts for the quantity produced. The distilleries have thereby become largely self-regulating.

The locks are still on it and the cabinet stays closed during distillation. The Spirits Regulations 1991 stipulate that a distiller may not build or change his installation in such a way that a non-approved process becomes possible, and that nobody may tamper with the installation or process. The returns go to HM Revenue and Customs.

The switch point of the cut determines which aroma compounds end up in the whisky, because each distillery sets that point to the flavour profile it is aiming for. The spirit safe is the instrument with which that choice is made.

The shop on the Brink in Bathmen stocks 3,898 whiskies, of which 2,783 are from Scotland, from 328 different brands. Every Scottish bottle among them has passed through such a cabinet. If you want to know how differently two distilleries handle their cut, drop by; we will walk you through the shelf.