The past two years have been very frustrating for home canners as canners searched and scrambled for two-piece lids. Out of frustration and desperation to get garden produce into jars, canners turned to using lids from uncertain suppliers, one-piece lids, reusable lids, and sadly reusing lids from previously canned foods (definitely a NO! NO!). It is hopeful that the canning lid supply and demand problem will be less in 2022, but it is not clear that the problem has gone away as the shelves of many reliable outlets remain void of lids at this time.
Despite the supply and demand issue with two-piece lids, the USDA and the National Center for Home Food Preservation (NCHFP) continue to recommend and support the two-piece lid system even though one-piece and reusable lids are available. Why the recommendation?
The two-piece lid system (flats and screw bands) is still the best option for home canners. They are easy to use, known to seal reliably, and easy to tell if the jars sealed. When researched guidelines are followed by users, the two-piece lid system safely replaces the vacuum system used for commercially canned foods with a self-sealing system consisting of a flat metal lid held in place by a metal screw band. A trough around the outer edge of the flat lid holds a rubber-like, plastisol sealing compound which acts like a gasket; heat causes the compound to flow slightly over the rim of the jar. During processing, the gasket allows air to escape from the jar and then forms an airtight seal as the jar cools.
To ensure safe home canned foods, follow these important tips for two-piece lids:
- Use new lids (flats) each time; after the first use the lid will no longer seal effectively. With careful handling, canning jars and screw bands may be reused many times.
- Purchase your lids (flats) from reputable suppliers.
- Buy only the quantity of lids (flats) that will be used in a year’s time—please don’t hoard.
- Follow the manufacturer’s directions for preparing lids (flats) to make sure to get a good seal.
- Carefully observe headspace requirements for the product.
- Removed air bubbles inside the jar with a plastic or silicone spatula.
- Make sure the rim of the jar is clean before placing the flat lid on the jar.
- Tighten the screw band as specified by the manufacturer. Usually this is fingertip tight, which means the first full resistance is felt using just your fingertips.
- Check all metal lids carefully. Don’t use old (more than 5 years old), dented, deformed, or defective lids.
- Do not re-use lids from previously canned foods.
One-piece, reusable, and previous used lids are not approved for home canning by the USDA as they may allow air to be trapped within the sealed jar permitting bacteria to thrive and spoilage to occur which can lead to illness and even death. While one-piece lids are available for home canning, they were made for use in industry where very strict time and temperature controls are in place. Because they do not allow air to escape properly in home canning, consumers have reported jar breakage and lids buckling.
Reusable canning lids have been around for decades . Research conducted through the National Center for Home Food Preservation on the reusable lids revealed that the three types of reusable lids they tested had an acceptable seal and removed the necessary amount of air. However, despite these finding, it was still recommended that the traditional two-piece metal lid system be used to “ensure the highest confidence in sealing.”  While there is no data to indicate that these lids will not perform satisfactorily if the manufacturer’s instructions are followed explicitly, the USDA and NCHFP cannot recommend their use due to a lack of researched-based information about their performance.
Lastly, recommendations and recipes from the USDA and NCHFP are currently based on the two-piece metal lid system. The recommendation does not come lightly; it is backed by a body of research documenting how well they work consistently for safe home canning.
Why take a chance? TWO-PIECE LIDS REALLY ARE NECESSARY.
North Central Food Safety Extension Network, North Dakota State University, Put a Lid on It, Best Practices for Using Closures for Home-based Canning, https://www.ncrfsma.org/files/page/files/fn2028_put_a_lid_on_it_fillable_information.pdf
University of Wisconsin-Madison Extension, Put a lid on It, Best Practices for Using Closures for Home-Based Canning, https://fyi.extension.wisc.edu/safefood/files/2021/04/Closures_2021.pdf