Do you heat canning lids, can you reuse them, and how tight is fingertip tight?
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Prepare canning lids the way the lid maker's box says. For current Ball and Kerr lids that means washing them in hot soapy water and using them at room temperature, with no simmering [1]. Use a new flat lid every time, because its sealing compound only seals once; bands can be reused for years if they are clean and not bent or rusted [2][3]. Tighten bands fingertip tight: turn until you first feel resistance, then stop [1][4]. Take the bands off once the jars have sealed. This page explains each of those answers and the reasons behind them, so you can troubleshoot a lid that buckles or fails.
The two pieces and what each one does
A two-piece canning closure is a flat lid (also called a dome lid) and a threaded band (also called a ring or screw band).
- The flat lid carries a ring of sealing compound, often called the gasket or plastisol, around its underside. During processing the compound softens and lets air escape from the jar; as the jar cools it seals the lid to the rim and holds the vacuum [2].
- The band only holds the lid in place while the jar is processed and cools. It does not seal the jar [4].
That division of labor explains all three rules on this page. The lid must be able to vent, so the band cannot be tight. The compound is shaped by one seal, so the lid cannot be reused. And once the vacuum holds the lid, the band has no job left.
Heating lids: only if your box says to
Not for current Ball and Kerr lids. K-State Research and Extension's Karen Blakeslee wrote in June 2026 that "Today's Ball® and Kerr® lids do not require preheating"; wash them in hot soapy water, dry them and use them [1]. University of Maine Extension says the maker of Ball lids stopped recommending preheating about ten years before its article, and that preliminary research suggests preheating may even be harmful, because it can lead to lids buckling during canning [5]. Blakeslee adds that boiling softens the sealing compound and can cause a premature seal [1].
That does not apply to every lid. University of Wisconsin food safety specialist Barb Ingham notes that other manufacturers may still call for preheating, and the rule is to follow the directions on the box you are using [4]. USDA's position is the same: prepare lids according to the manufacturer's directions [2][6]. If an older recipe or book tells you to keep lids simmering until you need them, check it against the box in your hand; the lids have changed.
Lid preparation by situation
| Your lids | What to do |
|---|---|
| Current Ball or Kerr lids | Wash in hot soapy water, rinse, dry, use at room temperature [1] |
| Another brand | Follow the directions on that box [4] |
| No directions (bulk lids, unknown brand) | Contact the seller or maker for directions before you use them for a tested process |
| Lids that are dented, bent, or have a gap or scratch in the compound | Discard them [2][4] |
| Lids more than about five years old | Unused compound works well for at least 5 years from manufacture; older lids may not seal [2] |
USDA's advice is to buy only as many lids as you will use within a year [2].
Reusing lids, bands and jars
Flat lids: no. Once a lid has sealed and been stored, the compound has been compressed and may not seal again [5]. NCHFP and USDA say to use new lids for each canning batch [2], Guide 7 says to "adjust new lids" on remade jam [6], and K-State says lids should never be reused [1]. A used lid is fine for keeping an opened jar in the refrigerator, or for dry pantry goods, where no seal is needed.
Bands: yes. Bands can be used again and again unless they are bent or rusted [3]. A bent band will not hold the lid flat, and rust flakes can end up on the rim.
Jars: yes. Mason-type canning jars can be reused many times with a new lid each time [2]. Check every rim for nicks before each use. Commercial jars from store-bought food are a different question, covered on which jars you can can jam in.
Fingertip tight, by feel
Screw the band on with your fingertips, not your palm or full grip, until you feel resistance, and stop there [1][4][5]. If you want a physical check, hold the jar still with one hand on a towel and turn the band with only the fingertips of the other; when it stops turning easily, it is done.
Both directions cause trouble:
| Band too loose | Band too tight |
|---|---|
| Jam can escape from the jar during processing [2] | Air cannot vent from the jar during processing [2] |
| The seal can fail [2] | The lid buckles, warps or creases near its edge [1][2] |
| Residue on the rim afterward | Possible jar breakage or seal failure [4]; food may discolor [2] |
Never tighten bands after processing. Retightening a hot lid can cut through the gasket and cause the seal to fail [7]. If a band feels loose when the jars come out, leave it alone; the band's job is nearly over.
Do not press on the center of a lid to "help" it seal, either. Ingham lists pressing lids to force a seal among the habits that cause failures [4].
Taking the bands off for storage
After the jars have cooled for 12 to 24 hours, remove the bands, test each seal and wash the outside of the jar and lid [7][8]. Stored bands trap moisture, rust and can be hard to get off later [2]. NCHFP recommends storing jars without bands to keep them dry [8]. Bands left on also hide a failed seal: a lid held down by a band can look sealed when it is not.
If you are giving or selling a jar and want a band on for looks, put a clean, dry band back on loosely after the seal is tested, and remove it if the jar goes back into storage. How to test a seal is on cooling jars and checking the seal.
When a lid buckles or doesn't seal
| What you see | Most likely cause | Fix next time |
|---|---|---|
| Lid warped or creased at the edge right out of the canner | Band too tight, or lid preheated when the maker says not to [1] | Fingertip tight; follow the box |
| Lid bulges days or weeks later | Possible spoilage producing gas [1] | Discard without tasting; see how to tell a jar has gone bad |
| Lid flexes when pressed after 24 hours | No seal | See the options on cooling jars and checking the seal |
| Several failures from one box of lids | Possible lid defect | Ingham suggests contacting the lid maker [4] |
Lids on jars you sell
Two-piece lids are the closure the home canning research was done with. Commercial makers often use one-piece lug caps on a hot-fill process, which is a different system with its own rules. If you are packing jam for sale, read jars and lids for jam you sell next.
References
- Kansas State University Research and Extension, Blakeslee, What Causes Canning Lids to Buckle?, You Asked It!, June 25, 2026. https://www.k-state.edu/news/you-asked-it/articles/2026/06/what-causes-canning-lids-to-buckle.html
- National Center for Home Food Preservation, Recommended Jars and Lids (from USDA Complete Guide to Home Canning, Agriculture Information Bulletin 539, revised 2015), viewed October 2026. https://nchfp.uga.edu/how/can/general-information/recommended-jars-and-lids/
- Cornell Cooperative Extension of Saratoga County, Whitten, Jars and Lids for Canning, undated, viewed October 2026. https://monroe.cce.cornell.edu/resources/jars-lids-for-canning
- University of Wisconsin-Madison Extension, Winnebago County, Ingham, Canning Update: Successful Jar Sealing, August 14, 2020, updated September 4, 2020. https://winnebago.extension.wisc.edu/2020/08/14/canning-update-successful-jar-sealing
- University of Maine Cooperative Extension, McCarty, No Need to Preheat Canning Jar Lids, undated, viewed October 2026. https://extension.umaine.edu/food-health/?p=14200
- USDA and National Center for Home Food Preservation, Complete Guide to Home Canning, Guide 7: Preparing and Canning Jams and Jellies, revised July 2015. https://nchfp.uga.edu/papers/guide/GUIDE07_HomeCan_rev0715.pdf
- National Center for Home Food Preservation, Cooling Jars and Testing Jar Seals (adapted from USDA Agriculture Information Bulletin 539, revised 2015), viewed October 2026. https://nchfp.uga.edu/how/can/general-information/cooling-jars-and-testing-jar-seals
- National Center for Home Food Preservation, Storing Home Canned Foods, viewed October 2026. https://nchfp.uga.edu/how/can/general-information/storing-home-canned-foods
