Each Scotch house has its own closely guarded blend, and while certain whiskies are not compatible, the bringing together of the right combination of malts and grains will determine the characteristics of the brand. Scotch whiskies age at different rate depending on where they were distilled as well as the location and the conditions in which they mature. Throughout the years of maturation, the whisky, which coming out of the still is a colorless spirit, gradually becomes more complex. Its color changes to, taking on an amber tint from the wood of the cask. By law, all Scotch whisky must be aged at least three years, and few brands enter the U.S. whithout being aged at least four years.
Many distillers also use barrels that once held sherry or wine.
The majority of single malts spend a minimum of five years in casks, although most are aged at least eight years, and some for much longer. In blends, when a Scotch is aged 10 years or 12 years, the number refers to the age of the youngest whisky in the blend. As is also the case with canadian whisky, Scotch can be bottled in the country of origin or it can be shipped in bulk to the U.S. and bottled here, which can be much more cost efficient. A 1964 act of Congress made that distinction. If the corn contents is higher, the product must be designated as corn whiskey.