Howdy johnb1963. The way to test the lids for sealing (other than looking for scratches and defects) is to pour a few ounces (quantity depends on the size or the jars) of hot, just off the boil, into the jar, place the lid on top (the screw on band is not required), and let the jar and water cool down. When the liquid and the steam cool down, it should great a vacuum in the jar. Removing the lid should make a slight sound of the vacuum being broken. if the lid is good. Since the lids (for our use) are not subjected to high heat (sterilization in boiling water) the seal on the lids does not break down as quickly as with canning. I have only hade to replace a couple of lids, due to my own miss handling! LOL!