I am new to canning. I made applesauce this morning and I pulled them out of the water bath and put them on a towel on my counter to seal, but I never heard the "ping" sound of them sealing shut. When does that usually occur? In the water bath? After the water bath? And if so, how long after you pull it out does that usually take? 5 min or 2 hours?
There's no real exact time it happens (at least in my kitchen). I've had some jars that come out of the water with the lid depressed and others that take many hours. By the next morning, they should be cooled with the lids depressed. If they aren't, then they should be reprocessed or refrigerated to be eaten right away. :)
The real goal is for the lid to turn concave. They're manufactured to be convex (sticking up in the middle). If they're concave on the jar, that means there's a difference in pressure between the inside and outside of the jar causing the lid to be sucked downward.
If the jar has cooled significantly, and the lid is still convex, you could try pushing down lightly on the lid. If it doesn't stay down, you don't have a good seal.