Place lids on jars, screw on rings and lower jars back into the pot of boiling water. The water should cover the jars; if not, add more. Boil jars for 10 minutes. Transfer jars to a folded towel and allow to cool for 12 hours; you should hear them making a pinging sound as they seal.Click to see full answer. Furthermore, what do you do if your jars don’t seal? How to Reprocess Unsealed Canning Jars Check each jar for nicks along the rim. If you find a nick, transfer the contents to a new jar. Reprocess the jars using the same processing time as before. Allow the jars to cool. Then, check for a good seal. Likewise, why are my jars not sealing? Liquid leaks out of jar during processing, leaving food particles on the sealing edge. Insufficient heat during processing – air not removed from jar so a vacuum seal never forms. (Remove air by inserting a rubber spatula or plastic knife inside the jar gently lift food to remove any trapped air.) how do you make a jar airtight? Step 1: Prick the Mason Jar Top. Using your thumbtack, create a small opening in the lid of the Mason Jar (or equivalent). Step 2: Fill Up Your Jar. Step 3: Seal the Jar. Step 4: Suck Out the Air. Step 5: Enjoy Your Airtight Containers! 2 Discussions. Why turn jars upside down?(Inverting is turning the filled jar upside down on its lid.) If the product cools down too much, the temperature of the product can become low enough to no longer be effective in sealing jars or preventing spoilage.