Siphoning is a term used to describe the problem of filling oozing out of jars while they are being processed in a canner. Overfilling the jars (not leaving enough headspace) is a common cause of siphoning. To avoid this, leave at least a one-inch headspace. Another cause of siphoning is extreme temperature variations. Make sure the filling is hot before adding it to the hot jars and lowering it into the hot water bath. Once the time is up, turn off the stove and leave the jars in the canner for an additional 10 minutes or until the water is cool.