No Need to Preheat Canning Jar Lids
— By Kate McCarty, Food Systems Professional, University of Maine Cooperative Extension
Dome lids play an important role in home canning. They, along with a screw band, protect your food from spoilage by creating a vacuum seal that forms during the canning process. So it’s important to prepare and apply dome lids and screw bands correctly during canning, as not following the proper procedure can result in jars failing to seal or buckled lids.
Update to Canning Lid Preparation
The proper way to prepare dome lids and screw bands for home canning is to simply wash them with warm, soapy water. That’s it! Many veteran home canners are used to preheating the dome lids in simmering water, but the manufacturer of Ball canning lids stopped recommending preheating lids about 10 years ago. Preliminary research shows that preheating lids may even be harmful, as it can cause lids to buckle during the canning process.
Buckled lids have a crimp or crease in them that occurs during canning and is typically caused by over tightening the screw band. Avoid over tightening screw bands by using only your fingers, not your whole hand, to tighten the screw band. This is called “fingertip tight.”
Jars with buckled lids are not considered sealed and should not be stored, although the food is still safe to eat if it is sealed and has not been at room temperature for more than 24 hours. Instead, refrigerate the food or transfer it to a freezer-safe container and freeze it.
Can I Reuse Canning Jar Lids?
Dome lids are recommended for one-time use. After a lid has been sealed and stored, the sealing compound becomes compressed and might not seal if reused. For best results, USDA recommends using new dome lids every time you can. Stock up on a box or two of each size so you are always prepared when the mood to can strikes. Screw bands can be reused as long as they are rust-free.
For more information about canning jars, lids, and equipment, visit the resources linked below. We also host hands-on workshops and virtual webinars on seasonal food preservation topics throughout the year.