What Is the Difference Between Single-Malt and Double-Malt Scotch?

Since a single-malt scotch can be a mixture of multiple barrels from the same distillery, almost all scotch is a form of blended whisky. The formal way to make a blended whisky is to mix scotch from both a barrel-aged whisky and a grain whisky. However, it can also be made when any two types of whisky are blended together and sold as one.