microwave has penetrability and changes with the frequency,the depth of penetration normally from several mm to tens of cm,both the outside and inside of the material can be heated at the same time,therefore avoiding the phenomenon of overheating of the outside while the inside uncooked.Microwave heating changes the heated object to be the heating object,no heat conduction will be necessary.It takes short time for the poor heat conductivity material to reach the heating temperature.The efficiency will be increased greatly by using the microwave,and also the productivity and the quality.