A mixing glass is used in cocktail making to mix and cool liquids. The mixing glass is used instead of a shaker when ingredients can be easily combined. Cocktails that consist only of spirits, for example, are stirred. For cocktails with clear ingredients, such as a martini cocktail, you prevent the drink from becoming cloudy by stirring it instead of shaking it. Shaking the drink in a shaker can produce quite a lot of meltwater. This is why drinks such as Old Fashioned, Manhattans, and Martinis are always prepared in a mixing glass.