Open kettle canning has not been recommended for 30+ years. Open kettle canning involves heating the food to boiling, pouring it into the jars, applying lids, and allowing the heat of the jar to cause the lid to seal. The food is not heated adequately to destroy the spoilage organisms, molds and yeasts that can enter the jar while you are filling the jar, and it does not produce a strong seal on the jar. This method is not safe! Just because the lid seals, doesn’t meat it’s safe. The time saved with open kettle canning is not worth the risk of food spoilage or illness.
Oven canning may sound simple, but oven heat is not the same as heat from a boiling water bath or from steam in a pressure canner. Placing jars in the dry heat of the oven may cause the glass to crack and shatter causing injury to you. Dry heat is not comparable to the moist heat of a boiling water bath. Processing in an oven will not heat the contents in the coldest part of the jar in the same way as boiling water. Oven heat will not increase the temperature inside the jar above boiling to be adequate to destroy botulism spores in low acid foods. Oven canning is not safe!
Source: http://bit.ly/2y6auUQ
