1. First preheat the oven to 1 10 degrees Celsius. Adjust the oven temperature to about 1 10℃ and preheat it for 15 minutes. Add grapes after the oven is preheated, otherwise the quality of raisins will be affected.

2. Wash the grapes and remove the fruit stalks. Wash the grapes with running water, and remove the larger fruit stalks with scissors or fingers. Throw away the bad grapes.

3. Grease the two baking pans on the guide rail, and then spread the grapes evenly inside. Spread a little vegetable oil or rapeseed oil on two framed baking pans, and then spread the grapes evenly on them. Try not to let the grapes touch each other.

Bake the grapes in the oven for about 4 hours, or until they shrink. Raisins must be dry enough, but not shriveled. During the baking process, check the grapes from time to time to avoid mistakes. If the grapes are dry enough, they can be taken out even if they have not been baked for 4 hours. The specific baking time depends on the size of the grapes and the degree of shrinkage you like. It takes longer for big grapes to dry.