Pressure Canning Guide

Pressure canning is the only safe method for preserving low-acid foods — meats, vegetables, beans, and soups — that can harbor Clostridium botulinum under improper processing. Done correctly, a jar of home-canned tomatoes or pressure-canned chicken stock will remain safe and nutritious for 12–18 months, often longer. Done incorrectly, it can produce botulinum toxin — odorless, colorless, and potentially fatal in amounts smaller than a grain of salt.

This guide covers both water-bath and pressure canning from jar preparation through storage. For a detailed comparison of when each method applies, see Water-Bath vs Pressure Canning.

Educational use only

This page provides general educational information about home food preservation. Improper canning can cause botulism — a potentially fatal illness. Always follow USDA-tested recipes and processing times. This information is not a substitute for the USDA Complete Guide to Home Canning. Use this information at your own risk.

Equipment and Startup Costs

Water-bath canner kit (pot, rack, lid, basic tools): affordable — available at any hardware or kitchen store Pressure canner (All American 915 or Presto 23-qt): moderate to significant investment depending on model Mason jars (12-count, quart): inexpensive new; reusable indefinitely if unchipped Ball Blue Book Guide to Preserving: inexpensive — the authoritative tested-recipe source

Total entry cost for water-bath canning is affordable. Adding a quality pressure canner raises the investment but unlocks all food categories.

The Core Safety Rule: Acidity Determines Method

All canning safety pivots on pH 4.6 — the threshold below which C. botulinum cannot produce toxin.

  • pH ≤ 4.6 (high-acid foods): water-bath canning is sufficient. Boiling water at 212°F (100°C) destroys pathogens and the acidic environment prevents botulism.
  • pH > 4.6 (low-acid foods): pressure canning only. C. botulinum spores survive boiling. Destroying them requires 240°F (116°C), achievable only at 10–15 PSI (69–103 kPa) in a pressure canner.

High-acid (water-bath): tomatoes with added acid, most fruits, jams, jellies, properly acidified pickles Low-acid (pressure only): green beans, corn, carrots, beets, meat, poultry, fish, soups, mixed meals, potatoes

Never water-bath low-acid foods

Botulinum toxin has no odor, no visible signs, and no taste. A sealed jar that looks and smells fine can still be lethal. The only safe mitigation is the correct process — not a sniff test.

Water-Bath Canning: Step-by-Step

What You Need

  • Water-bath canner with rack (or any deep pot ≥12 in / 30 cm deep with a rack to keep jars off the bottom)
  • Mason jars in good condition — no chips, cracks, or star fractures
  • New two-piece lids (bands can be reused; flat lids must be new each time)
  • Jar lifter, wide-mouth funnel, bubble remover or thin spatula
  • USDA-tested recipe (Ball Blue Book, National Center for Home Food Preservation)

Step 1 — Prepare the Canner and Jars

  1. Fill the canner halfway with water; begin heating on high.
  2. Wash jars in hot soapy water or run through dishwasher.
  3. Keep jars hot until filling — set them in the canner's simmering water or in a 170°F (77°C) oven. Hot jars prevent thermal shock cracking.
  4. Wash lids in hot soapy water; do not pre-boil modern lids — the compound softens at too-high temperatures.

Step 2 — Prepare the Food

Follow your tested recipe exactly. Do not alter proportions, substitute ingredients, or change pack densities — these changes affect heat penetration and acidity.

Headspace by food type:

Food Headspace
Jams and jellies ¼ in (6 mm)
Fruits, tomatoes (hot pack) ½ in (13 mm)
Fruits (raw pack), pickles ½ in (13 mm)

Incorrect headspace prevents proper vacuum seals or causes siphoning (liquid loss).

Step 3 — Fill Jars

  1. Use a funnel to fill jars to the measured headspace.
  2. Run a bubble remover or spatula around the inside edge to release trapped air bubbles.
  3. Wipe the jar rim with a clean damp cloth. Any residue prevents a good seal.
  4. Center the flat lid on the jar. Apply the band until finger-tight — snug, not cranked down. Over-tightening prevents air from venting during processing.

Step 4 — Process

  1. Lower jars into the canner with a jar lifter. Jars must be covered by at least 1–2 in (2.5–5 cm) of water.
  2. Cover the canner and bring to a full rolling boil.
  3. Begin timing only when a full rolling boil is reached.
  4. Process for the full recipe time. Do not lift the lid during processing.

Altitude adjustments for water-bath canning:

Altitude Add to Processing Time
0–1,000 ft (0–305 m) No adjustment
1,001–3,000 ft (306–914 m) +5 minutes
3,001–6,000 ft (915–1,829 m) +10 minutes
6,001–8,000 ft (1,830–2,438 m) +15 minutes
Above 8,000 ft (2,438 m) +20 minutes

Step 5 — Cool and Verify

  1. Remove jars without tilting using the jar lifter; set on a towel-covered counter at least 1 in (2.5 cm) apart.
  2. Do not press the lid centers, adjust lids, or cover jars during cooling.
  3. Listen for the satisfying "ping" of sealing within 30 minutes.
  4. After 12–24 hours, test every seal: press the center of the lid. A properly sealed lid does not flex up and down. Remove the band and gently try to lift the lid by its edges — a good seal holds firm.
  5. Any jar that did not seal must be refrigerated and used within 1–2 days or reprocessed within 24 hours with a new lid.

Pressure Canning: Step-by-Step

Pressure canning is the only approved method for all low-acid foods. The process is not dangerous when done with a functional canner and tested recipes — fear of pressure canners causes more harm (by defaulting to unsafe water-bath methods) than it prevents.

Step 1 — Inspect Equipment

  • Check the gasket on the canner lid — it should be pliable, not cracked or brittle.
  • If you have a dial-gauge canner, have the gauge tested yearly at your local Cooperative Extension office. Dial-gauge errors are a real failure mode.
  • Weighted-gauge canners (like All American) do not require calibration.
  • Clean the vent pipe and petcock with a pipe cleaner.

Step 2 — Prepare Jars and Food

Same process as water-bath: hot jars, tested recipe, correct headspace.

Headspace for pressure canning:

Food Headspace
Meats and poultry 1¼ in (32 mm)
Vegetables, soups 1 in (25 mm)

Step 3 — Load the Canner

  1. Add 2–3 qt (1.9–2.8 L) of hot water to the canner (or per manufacturer — typically 2–3 in / 5–7.5 cm depth).
  2. Set the rack in place, load jars, lock the lid.
  3. Heat on high with the weight or petcock open (vent position).

Step 4 — Vent the Canner

This step is not optional. Before applying pressure, the canner must exhaust (vent) for a full 10 minutes. This purges air from the headspace of jars and from the canner interior. Air pockets reduce internal temperature and create processing failures even when the gauge reads correctly.

  1. Heat with vent open until a steady stream of steam vents for 10 minutes.
  2. Place the weighted gauge or close the petcock to bring the canner to pressure.
  3. Let pressure build to the recipe's target.

Step 5 — Process at Pressure

  1. Start timing only when pressure reaches the recipe target.
  2. Adjust heat to hold pressure steady — fluctuations are acceptable within ±1 PSI (±7 kPa).
  3. Do not let pressure drop below target at any point; if it does, bring it back up and restart the timing from zero.

Pressure targets by altitude (weighted gauge):

Altitude Pressure
0–1,000 ft (0–305 m) 10 lb (69 kPa)
Above 1,000 ft (305 m) 15 lb (103 kPa)

Pressure targets by altitude (dial gauge):

Altitude Pressure
0–2,000 ft (0–610 m) 11 PSI (76 kPa)
2,001–4,000 ft (611–1,219 m) 12 PSI (83 kPa)
4,001–6,000 ft (1,220–1,829 m) 13 PSI (90 kPa)
6,001–8,000 ft (1,830–2,438 m) 14 PSI (97 kPa)

Step 6 — Depressurize and Remove Jars

  1. Turn off heat when processing is complete.
  2. Let the canner depressurize naturally — do not run under cold water or try to speed this. Natural depressurization takes 30–60 minutes.
  3. When the pressure gauge reads zero AND the safety button (if present) drops, wait an additional 10 minutes before opening.
  4. Tilt the lid away from you when opening to direct steam away from your face.
  5. Remove jars without tilting; cool and verify seals using the same procedure as water-bath.

Common Processing Times (USDA)

Food Jar Size Method Time at Sea Level
Tomatoes (acidified) Pint (473 mL) Water-bath 35 min
Tomatoes (acidified) Quart (946 mL) Water-bath 45 min
Green beans Pint (473 mL) Pressure (10 PSI) 20 min
Green beans Quart (946 mL) Pressure (10 PSI) 25 min
Chicken (boneless) Pint (473 mL) Pressure (10 PSI) 75 min
Chicken (boneless) Quart (946 mL) Pressure (10 PSI) 90 min
Beef stew Quart (946 mL) Pressure (10 PSI) 90 min
Strawberry jam Half-pint (237 mL) Water-bath 10 min

Always verify times in a current USDA-approved publication. Times are updated periodically.

Storage, Rotation, and Rejection

Store canned goods in a cool (50–70°F / 10–21°C), dark location. Heat and light degrade both quality and seal integrity over time.

Best-by guidelines: - High-acid foods (fruits, jams, pickles): best within 12–18 months - Low-acid foods (vegetables, meats): best within 2–5 years for quality; safe indefinitely if seal intact

Discard any jar that shows: - Lid that flexes up and down (broken vacuum) - Spurting liquid when opened - Off odor (any odor at all in low-acid foods is a red flag) - Mold, foam, or unusual color - Corrosion around the lid rim - Any jar you dropped or that shows impact damage

Field Note

If you've never canned before, do your first batch with strawberry jam. The process is forgiving, the consequences of a minor error are minimal (it just won't seal, not botulism), and success is obvious. Master the water-bath first before moving to pressure canning. That sequential skill-building catches procedural errors on low-stakes batches.

Building a Canning Rotation System

Canning integrates naturally with Pantry and Long-Term Storage planning. The goal is a living inventory — jars go in at harvest and come out in rotation throughout the year.

  • Label every jar: contents, date, processing method, altitude adjustment applied
  • Store newest jars at the back, oldest at the front
  • Audit the pantry every 3 months; any jar past 24 months gets opened and used regardless
  • Track what got canned vs what got eaten — this reveals what to grow or buy more of next season

For a full rotation framework, see Food Inventory.

Practical Checklist

  • Identify whether your recipe is high-acid or low-acid; match to correct method
  • Source a USDA-tested recipe (Ball Blue Book, NCHFP website)
  • Inspect all jars for chips or cracks before filling
  • Apply altitude adjustment to all processing times
  • Vent pressure canner for 10 full minutes before applying pressure
  • Time processing from full boil (WB) or target pressure (PC) — not from when heat was applied
  • Test every seal after 12–24 hours cooling
  • Label all jars with contents, date, and processing method
  • Track your pantry inventory with Food Inventory

Pressure canning gauge cross-section showing color-coded zones: 0–5 PSI danger zone where spores survive, 10 PSI standard processing at 240°F/116°C, and 15 PSI high-altitude setting required above 1,000 ft/305 m