Tighten the ring (ring lid) onto the jar with your fingertips until you feel resistance — do not overtighten .
The lid must make good contact with the glass , but the ring must not be too tight .
Do not use full force or tools — only your hands, with light pressure.
Why not tighter?
Air must be able to escape from the jar during heating.
If you tighten the lid too much, the air cannot escape. The mason jar will then not vacuum properly, and both the lid itself and the rubber seal can deform or tear. Your jars may also start leaking during canning.
