If you were to build a distillery from scratch it would not look anything like Old Bushmills. This higgledy-piggledy collection of red brick and slate is full of character, but these listed buildings are all that remain of an earlier age of red brick, water wheels and steam.

New uses have to be found for old buildings and any expansion has to be done sensitively. You cannot afford to sacrifice the charm that made Old Bushmills special in the first place.

There needs to be living space for Peter the Pheasant, who escaped from a nearby shooting estate and found sanctuary in the distillery grounds, and creative space for Liz to create classics like the to-die-for Bushmills Cheesecake she makes for the visitors café.

It is an eccentric place. The trick then is to make the best of what is there, while keeping in mind what is really important — the character of the whiskey itself. So in the past hundred years, while a lot of things have changed, it is the attention to detail that continues to make Old Bushmills whiskey so special.

For a start, then as now Old Bushmills whiskey has always been made from the same three things:

Water, yeast and malted barley. That's the chemistry.

I like to add a fourth item to the list: Time. That's the magic.

Water

Water is easy. It is everywhere. If you are visiting Co. Antrim, bring an umbrella because it won't be long before you will need to use it. There is a joke that around here even the sheep have webbed feet. But we have to be thankful for all this rain, because without it there would be no whiskey. That is because the water used in the making of Old Bushmills has always come from the same source, St Columb's Rill, a small stream and a tributary to the River Bush, which flows through the distillery grounds. The Ivater from this stream is gathered in a pool outside the distillery, before being pumped inside, where the magic can begin.

Yeast

For something quite amazing, yeast is pretty dull. It is kind of a crumbly butter coloured cake, but it is a living organism, and it just loves sugar. Yeast is the magic ingredient that gives us two very useful by-products: alcohol, without which there would be no beer or whiskey; and CO2, without which we would have only flat bread.

Malted Barley

Barley is a grain. It looks a bit like wheat and it thrives in the cooler, damp climates of Ireland and Scotland.

Malt then is the third and final ingredient needed to make whiskey. Malted barley is simply barley that has been allowed to sprout. To make malt you need to confuse the barley into thinking that spring has arrived. The barley is soaked in water then kept nice and warm. It's like a perfect May week in Ireland: the conditions are ideal for growing, and after 4 to 5 days the barley starts to germinate.

What happens is that the cell walls break down, and the long strings of starch shorten to become simple sugars. This is the food which the plant will need to grow, but this is also the sugar we need to make whiskey. So the germination has to be stopped before the tiny seed starts 'eating itself'.

For all our science, the malting process is still very intuitive. It takes the considerable skills of the maltster to know when to stop the germination. Usually this is when the rootlet is around the same length as the grain.

A blast of heat is the best way to stop germination in its tracks, and what you use to generate that heat will affect the final flavour of the whiskey. Nowadays Irish barley is malted in large rotating drums using hot dry air, but that was not always the case.

Until 1972 Bushmills had its own maltings (now the distillery café — did I mention the cheesecake?). Here the fire that would dry the barley was started with peat that was dug locally and carried to the distillery. Once the fire was going, coal would be used; this meant that the barley was only exposed to peat smoke for a brief time. Ronnie Brennan, who worked at the distillery during this period, said it gave the whiskey a "very soft taste".

During the mid-1970s Irish Distillers, who owned the plant then, experimented with a very heavily peated malt, but according to Ronnie it just didn't work. The whiskey made at Old Bushmills does not need to get its flavour from 'peat reek'.

Two different kinds of whiskey come into play at Bushmills.

First up are Single Malts: the ten-year-old, the sixteen- year-old and the twenty-one-year-old. These are made, matured and bottled on site. Bushmills is the only place in Ireland that does this.

Then there are the blends: Bushmills Original, Black Bush and 1608. These are made by blending malt and grain whiskeys. Grain whiskey has never been produced at Bushmills; it used to be made at Coleraine. Today Bushmills sources grain whiskey from Midleton. Staff at Bushmills insist that they only source grain 'spirit' from Midleton, distilled to their own specification, to be casked at Bushmills, technically becoming Irish whiskey only after 3 years at the Co. Antrim distillery.

Written by Peter Mulryan

The text is an excerpt from "Bushmills: 400 Years in the Making" (pp. 155 - 160), written by Peter Mulryan, published 2008 by Appletree Press Ltd.