Once a grape is dried, it becomes a raisin. The first step in raisin production is harvesting grapes. Grapes are first pre-treated with a cold dip. This helps the water evaporate through the thick grape skin. Then the grapes are dried. Sun drying is inexpensive, but can be slow and increases the risk of pests. Mechanical drying causes rapid evaporation and is a quicker and more controlled process. Once dry, the raisins are sent to a processing plant to remove any stems or foreign objects.