What is water bath canning?
Water bath canning, also called boiling water canning, heats filled jars in a pot of boiling water to destroy spoilage organisms and seal the jar. It is used for high-acid foods, such as many fruits, jams and jellies, and properly acidified pickles and tomato products prepared by a tested method.
It is a heat treatment, not just a way to get a lid to pop. The seal keeps new germs out, and the heat treatment must be enough for the specific food, jar and recipe.
Ask your extension office whether a hands-on class is offered in your area. Seeing the steps done by an experienced person makes written recipes much easier to follow.
Which foods are suited to water bath canning?
The method is for foods that are acidic enough to prevent dangerous bacteria from growing. Low-acid foods, such as plain vegetables, meat, poultry, fish and soups, are not safe for water bath canning and require a pressure canner using tested instructions.
Do not guess at acidity. Foods can be borderline, and acidity can change with ingredients. Use only tested recipes from the National Center for Home Food Preservation at nchfp.uga.edu, the USDA Complete Guide to Home Canning or your extension office, and never change ingredient proportions.
- High-acid foods only
- Tested recipes with their exact proportions
- Never substitute or reduce acid or add low-acid ingredients on your own
- Low-acid foods need a pressure canner
What equipment do you need?
You need a large pot with a rack and lid, jars made for canning, new lids as the manufacturer directs, a jar lifter, a funnel and a way to measure and clean the rim. Use jars made for home canning, not decorative or reused commercial jars unless a tested source says they are suitable.
Check jars for chips and cracks before each use. Follow the tested recipe for jar size, headspace, preparation and processing. Those details are not interchangeable, and this article does not give times or amounts because they must come from the tested source.
Set up your work area before you start: clean counters, a clear path from stove to cooling spot, and a towel-covered surface where hot jars can rest away from drafts. Cold drafts and sudden temperature changes can crack jars.
What does the process look like in general terms?
In general, you prepare the food as the tested recipe directs, fill clean jars, remove air bubbles, wipe the rims, apply lids, heat the jars as the recipe says, then cool them undisturbed. Each step has a reason, and skipping one can compromise safety.
Processing details depend on the recipe, jar size and your elevation, so follow the instructions from your tested source and ask your extension office how local conditions affect your recipe.
Elevation matters for canning, and the tested recipe will tell you how to account for it. If you do not know your elevation, look it up or ask your extension office, and then follow the adjustment stated in the tested source.
How do you check the results?
After the jars cool, check that lids are sealed and do not flex. Label jars with the food and date, remove rings if your tested source advises, and store jars in a cool, dark, dry place. Any jar that did not seal should be handled as your tested source directs, for example by refrigerating or reprocessing within the stated limits.
Before you open any jar later, look for leaks, bulging lids, off smells, mold, spurting liquid or cloudy contents. Discard any such jar without tasting. When in doubt, throw it out.
Keep jars from different batches separate and labeled, so if one batch has a problem, you know which jars to check. Use the oldest jars first and plan on using canned goods within the period your tested source recommends for best quality.
What are the common mistakes and costs?
Common mistakes include using untested or old recipes, changing proportions, using the wrong jars, skipping headspace or rim cleaning, and using a water bath for a low-acid food. Each is avoidable with a tested recipe and a careful routine.
Costs fall into categories: a canner and rack, jars, new lids, ingredients, fuel or power, and storage shelving. Jars and a canner can be reused for years, so most of the ongoing cost is lids, ingredients and your time.
Do not stack heavy jars, and keep storage shelves sturdy. A shelf collapse is a safety hazard as well as a loss of food. Check storage areas for moisture and pests.
Key takeaways
- Water bath canning is for high-acid foods only.
- Use current tested recipes from NCHFP, USDA or extension, and never change them.
- Use canning jars in good condition and new lids as directed.
- Check seals and discard any suspicious jar without tasting.
- Low-acid foods need a pressure canner.
Sources and further reading
Last reviewed: November 12, 2026. Written by the Homestead & Small Farm Editorial Team. See our editorial policy.