When Do Canning Jars Seal? Timing and Lid Checks

After processing, place jars upright on a towel or cooling rack with space between them. Do not tighten bands, press lids, or turn jars upside down while they cool; check the seals after 12 to 24 hours.

Once the jars are cool, remove the screw bands and press the center of each lid. A properly sealed lid should be concave and should not flex or pop; you can also gently lift the jar by the edge of the lid to confirm it holds.

If a lid did not seal, refrigerate the food and use it soon, freeze it in a suitable container, or reprocess it within 24 hours using a new lid and the full processing time from a tested recipe. Check the jar rim for chips or food residue before reprocessing, and do not store an unsealed jar at room temperature.

A vacuum-sealed lid does not make an unsuitable jar safe for heat processing. Use jars, lids, and a tested recipe intended for the canning method; a decorative glass storage jar should be treated as storage-only unless its manufacturer specifically rates it for canning. For details about the featured jar, see the vintage embossed glass storage jar guide.