Ice may be used in cocktails in a number of ways: cubes, cracked (lump), crushed or shaved (snow).
Cracked Ice
Cracked (or lump) ice consists of cubes that have been roughly broken down into smaller pieces. You can make cracked ice at home by simply placing some whole ice cubes into a bag or tea towel. Lay the cubes out on a board so that you have a single layer of cubes, and hit them firmly with a mallet or meat tenderizer. Each cube should only be broken once or twice.
Crushed Ice
Crushed ice is ice that has been broken down further than cracked ice. This may be carried out in a blender; however, you should always break the cubes up (as above) before adding them to the blender to prevent the risk of any damage to the machine. As the crushed ice will liquefy quickly, it is important to produce it immediately before use, making sure that the glass to be used is well chilled.
Shaved Ice
Shaved ice (or snow) is even finer than crushed ice, and is usually made in a special machine that shaves the ice cubes into fine snow.