Scotch whisky is obtained primarily from barley, which is grown in Scotland preferably, but of late year’s barley from California, Canada, India, Africa, and other countries has been imported for distilling purposes.
There are five main processes in the making of Scotch: first, malting; second, mashing; third, fermenting; fourth, distilling; and fifth, maturing and blending.
On arrival at the distillery, the barley goes into the barley-receiving room where it is dressed, that is, sieved, or passed over screens so that small and inferior grain will be eliminated, after which the best grain is stored. When required for use, it is placed in tanks, called “steeps,” where it is soaked in water until thoroughly softened. It is then spread out on the floor of the malting house, and sprinkled with warm water for about three weeks, during which time the grain begins to germinate, that is, to sprout.
When the sprouts are about three-quarters of an inch long, the water is turned off and the grain is known as “green malt.” Please note that it is already malt, for malt is germinated grain. During this germination process, a chemical change has occurred in the grain which is important in its future function of producing whisky. Some of the starches have been changed into diastase, which has the property of converting the balance of the starch into sugars-maltose and dextrin-which are fermentable, whereas the starch in its original state is not.
The green malt is transferred to a kiln, where it rests on a screen directly above a peat (Peat is coal in its primary stage, and consists of partially carbonized vegetable material, usually found in bogs. Pressed and dried peat is generally used for fuel in both Scotland and Ireland.) fire. Like green wood, peat gives off a much more acrid and oily smoke than soft coal. This swirls around the grain, which becomes so impregnated with the aroma of the smoke that it is carried over into the spirit later distilled from it.
The kilning, or drying, process is very important, as it is here that the malt acquires a good part of its character, and a variation occurs here in the various regions; that is, the malt in the Lowlands is kilned less than in the Highlands; whereas the Campbeltown and Islay grains are more heavily roasted.
The kilned malt is now screened to remove the culm or dried sprouts, after which it goes to the mill room where it is ground into meal or “grist.”
The next step is mashing. The ground malt is thoroughly mixed with warm water in a mash-tub where it soaks until the water has liquefied all of the starches, and the diastase has converted them into sugars. When the water has absorbed all of the goodness from the grain, it is drawn off, cooled, and is known as wort.
The wort now passes into the fermenting vats where a small quantity of carefully cultivated pure yeast is added and fermentation takes place. The yeast acts upon the sugars in the wort in the same manner as the natural yeasts act upon the sugars in grape juice, producing alcohol and carbonic acid gas. When fermentation is completed, the liquid is known as beer, or wash. Up to this point the process is identical with that of the brewing of ales and beers, except for the omission of hops.
The beer now goes into a pot still which is known as the wash still. The result of the first distillation is a distillate of low alcoholic strength, which is known as low wines. The low wines pass into the spirit still where they are redistilled. The first and last part of the distillation (the heads and tails called the feints) is gathered separately from the middle portion, which is the useful part of the distillation. At the beginning and at the end of the distillation operation, too high a percentage of impurities are carried over with the spirit, which, if used, would impair the flavor of the spirit when matured. The feints, however, contain a substantial quantity of useful alcohol and are returned to the spirit still with the next charge of low wines, and the alcohol is distilled out. The impurities are disposed of with the residual slop from the spirit still operation, that is, the waste material which is thrown out.
The useful spirit, distilled off at between 140 and 142 proof, is now known as whisky, and flows into a spirit vat from where it is put in casks. These casks, generally made of American white oak, vary in size from 33 to 144 American gallons in capacity. The different sizes are used for convenience. They may be new or old, and very often are casks in which Sherry has been shipped. More often than not, the casks have been previously used for maturing whisky.
At the time of barreling the whisky is reduced in proof to 124 to 126.8 by the addition of water. According to Dr. P. Schidrowitz, whose notes are quoted by Peter Valaer in his excellent paper on Scotch whisky, “it is held that the best water is that which its origin as a spring has served with water which has passed through a red granite formation, and which, after rising from its source, passes through peaty country. Such waters are generally very soft, and possess certain qualities which are apparently due to the peaty soil or heather-clad moor through or over which the water passes on its way to the distillery.” The waters of Loch Katrine are reputed to be of the finest for Scotch whisky.