Experience has shown that to thaw products more than a few centimeters thick using microwaves, surface cooling is necessary. The study presented here shows the amount of frigorific energy required as a function of the thickness of the product and the end temperature.The cooling process using sprayed cryogenic liquids under electrostatic high voltage, developed at (Renardieres) EDF research center, permits the fulfilment of the requirements herein defined. The results demonstrate the possibility of thawing the center and throughout, regardless of the thickness of the product.