Dampness may corrode bands or metal lids and cause leakage which will spoil the contents. Jars do not need to be sterilized before canning if they will be filled with food and processed in a boiling water bath canner for 10 minutes or more or if they will be processed in a pressure canner, however it is good practice to take the extra time and sterilize anyway. You can never be too careful when it comes to food safety. Jars that will be processed in a boiling water bath kettle for less than 10 minutes need to be sterilized by boiling them in hot water for 10 minutes before they're filled. This can be dangerous because the temperature will vary according to the accuracy of oven regulators and circulation of heat.
Dry heat is very slow in penetrating into jars of food.
Also, jars explode easily in the oven. If the pot is not exhausted, the inside temperature may not correspond to the pressure on the gauge. Steam should be allowed to escape for 10 minutes before closing the valve. Loss of liquid does not cause food to spoil, though the food above the liquid may darken. Lids should never be used a second time since the sealing compound becomes indented by the first use, preventing another airtight seal.