Common Canning Mistakes and What to Do Instead
Avoid common home-canning mistakes with simple, research-tested practices for safer, better-quality food.
Home canning is a practical way to preserve a garden harvest, but it isn’t a good place to improvise. Safe canning depends on using a research-tested recipe and following the specified ingredients, jar size, processing method, time, pressure, and altitude adjustments.
Here are some of the most common canning mistakes, ranked by risk, along with what to do instead.
Risk levels are a quick guide: High-risk mistakes can affect food safety; medium-risk mistakes can interfere with proper processing or sealing; low-risk mistakes mainly affect quality, texture, or convenience.
High-Risk Canning Mistakes
1. Using an untested canning recipe
Risk: HIGH
Mistake:
Using a family recipe, random internet recipe, or recipe designed only for cooking rather than canning.
Instead:
Use a current, research-tested canning recipe from a reliable source such as the USDA, National Center for Home Food Preservation, or a Cooperative Extension program.
Why:
Canning recipes are tested around specific ingredients, proportions, jar sizes, processing methods, temperatures, and times. A recipe that tastes good or produces a sealed jar has not necessarily been tested for safe preservation.
2. Changing a tested canning recipe
Risk: HIGH
Mistake:
Changing ingredient proportions, substituting ingredients, or reducing the amount of acid called for in a tested recipe.
Instead:
Follow the recipe as written unless the source specifically provides an approved substitution or adjustment.
Why:
Even seemingly small changes can affect how heat moves through the food or how acidic the finished product is. This is especially important when canning low-acid foods and acidified foods such as tomatoes.
3. Using the wrong canning method
Risk: HIGH
Mistake:
Using a boiling-water canner for a food that requires pressure canning.
Instead:
Use the processing method specified by the tested recipe. In general, low-acid vegetables, meats, and other low-acid foods require pressure canning, while properly acidified high-acid foods can be processed using a boiling-water or atmospheric steam canner when the tested recipe calls for it.
Why:
Boiling water does not reach a high enough temperature to safely process low-acid foods. Pressure canning reaches the higher temperatures needed for these foods.
Related: How to Preserve Your Garden Harvest: A Quick Guide to Freezing, Drying, and Storage
4. Using a pressure cooker instead of a pressure canner
Risk: HIGH
Mistake:
Assuming a pressure cooker or electric multicooker can safely replace a pressure canner.
Instead:
Use a pressure canner specifically designed and tested for pressure canning, and follow the instructions for the tested recipe and your canner.
Why:
Pressure cooking and pressure canning are not interchangeable processes. Some appliances sold with a “canning” setting have not been established as safe for pressure canning.
The same rule applies to other shortcuts such as oven canning, microwave canning, and so-called dry canning methods. A jar that develops a seal after heating is not proof that the food was safely processed.
5. Assuming a sealed jar means the food is safe
Risk: HIGH
Mistake:
Seeing a sealed lid and assuming the food inside must be safe.
Instead:
Make sure the food was prepared from a tested recipe and processed using the correct method, time, pressure, jar size, and altitude adjustment.
Why:
A vacuum seal helps protect processed food from new contamination, but the seal itself does not replace the processing step. Safe canning depends on the complete process.
6. Ignoring altitude adjustments
Risk: HIGH
Mistake:
Using sea-level canning instructions without checking your elevation.
Instead:
Check your elevation and follow the altitude adjustment given with the tested recipe.
Why:
Water boils at a lower temperature as elevation increases. For boiling-water and atmospheric steam canning, processing time generally needs to increase. For pressure canning, the required pressure may change depending on the type of pressure canner.
7. Guessing at pressure or processing time
Risk: HIGH
Mistake:
Using more pressure because it seems safer, shortening the processing time because you’re in a hurry, or allowing pressure to drop without following the recipe’s instructions.
Instead:
Use the exact processing time and pressure specified for your food, jar size, canner, and elevation. If pressure falls below the required level during pressure canning, follow the tested instructions for restarting the process.
Why:
Safe canning depends on a specific combination of time, temperature, and pressure. More pressure is not a substitute for following the tested process.
Related: How to Freeze Corn From the Garden
Medium-Risk Canning Mistakes
8. Using damaged or unsuitable jars
Risk: MEDIUM
Mistake:
Using jars with cracks, chips, deep scratches, or commercial jars that aren’t appropriate for the food and processing method.
Instead:
Use Mason-type home-canning jars designed for the type of processing you’re doing, and inspect them before every use.
Why:
Damaged jars can break during processing, while some commercial single-use jars are more prone to breakage or seal failure. NCHFP notes that some commercial mayonnaise-style jars can be used for certain acid foods with new two-piece lids, but they are not recommended for pressure canning. For a general home-canning rule, purpose-made canning jars are the better choice.
9. Getting headspace, air bubbles, or jar rims wrong
Risk: MEDIUM
Mistake:
Filling jars too full, leaving too much space, trapping air in the food, or leaving food on the sealing surface.
Instead:
Use the exact headspace specified by the tested recipe, remove air bubbles as directed, and wipe the jar rim clean before applying the lid.
Why:
Headspace gives food room to expand during processing and helps the lid form a proper seal. Food or liquid on the rim can also interfere with sealing.
10. Mishandling jars while they cool
Risk: MEDIUM
Mistake:
Moving hot jars onto a cold surface, putting them in a draft, tilting them unnecessarily, or tightening the bands after processing.
Instead:
Remove jars carefully with a jar lifter, place them on a protected surface away from drafts, and leave them undisturbed while they cool according to the tested instructions.
Why:
Hot jars can break when exposed to sudden temperature changes. During cooling, the contents contract and create the vacuum that holds the lid in place.
11. Using or preparing lids incorrectly
Risk: MEDIUM
Mistake:
Treating every type of canning lid the same or reusing disposable flat lids.
Instead:
Use the lid system specified for your canning setup and follow the manufacturer’s preparation and tightening instructions. For standard two-piece metal lids, use a new flat lid and a compatible screw band.
Why:
Lids need to vent during processing and then form a reliable vacuum seal as the jar cools. Over-tightening can interfere with venting and sealing, while loose bands can allow liquid to escape. Standard flat metal lids are designed for one use; screw bands can be washed, dried, and reused if they remain in good condition.
12. Storing canned food incorrectly
Risk: MEDIUM
Mistake:
Leaving finished jars in direct sunlight, somewhere hot or damp, or storing them with dirty or wet screw bands attached.
Instead:
After jars have cooled and been checked for seals, remove the bands, wash and dry the jars, and store them in a clean, cool, dry, dark place.
Why:
Heat, light, and moisture can reduce food quality, corrode metal components, and contribute to seal problems. The vacuum seal—not the screw band—is what holds a properly sealed jar closed during storage.
Lower-Risk Canning Mistakes
13. Using poor-quality produce
Risk: LOW
Mistake:
Using moldy, diseased, badly damaged, or overripe produce because you hope canning will rescue it.
Instead:
Start with sound, good-quality produce and remove damaged portions as directed by the tested recipe.
Why:
Canning preserves food; it doesn’t turn poor-quality produce into good-quality food. Fresh, suitable produce generally gives you better flavor, texture, and appearance in the finished product.
14. Doubling jam or jelly recipes
Risk: LOW
Mistake:
Doubling a tested jam or jelly recipe to save time.
Instead:
Make separate batches unless the tested recipe specifically gives instructions for a larger batch.
Why:
Larger batches can take longer to cook and may not reach the proper jelling point consistently. NCHFP specifically recommends making small batches and not doubling tested jam and jelly recipes.
Related: Gardener’s October To-Do List by USDA Zone
15. Expecting every jam or jelly to set immediately
Risk: LOW
Mistake:
Deciding a batch has failed simply because it isn’t fully set as soon as it cools.
Instead:
Follow the tested recipe’s instructions and give the finished product the recommended time to cool and set before deciding whether there is a problem.
Why:
Jellied fruit products can fail to set for several reasons, including ingredient proportions and cooking conditions. If a batch doesn’t set, use the tested troubleshooting guidance for that recipe rather than automatically remaking it.
One More Important Canning Rule
Don’t use the jar seal as your only safety check.
If a jar is unsealed, leaking, visibly spoiled, or otherwise questionable, don’t taste the food to see whether it is still good. Follow the tested guidance for handling an unsealed jar, or discard questionable food when in doubt.
Safe home canning doesn’t require memorizing dozens of complicated rules. The most important habit is to stop improvising where the tested process matters: use a reliable recipe, use the correct equipment and processing method, make the required adjustments for your elevation, and follow the instructions from start to finish.
