Pressure Canning: Complete Guide with Altitude Adjustments

Equipment

Pressure canner: A large pot with a locking lid, pressure gauge, and safety relief valve. Holds at least 4 quart jars or 7 pint jars. Do NOT use a pressure cooker. Brands: Presto, All American (weighted gauge), Ball.

Two gauge types:

• Weighted-gauge canner: Uses a weight that rocks or jiggles at 5, 10, or 15 lbs pressure. Does not require calibration. Preferred for reliability.
• Dial-gauge canner: Reads exact pressure. Must be tested for accuracy annually at your local extension office.

Jar and lid terminology:

• Mason jars (Ball, Kerr): For home canning. Regular-mouth and wide-mouth, pint and quart sizes.
• Lids: Two-piece — a flat disk lid (single use, contains sealing compound) and a screw band (reusable).
• Never reuse flat lids. The sealing compound deforms on first use. Bands can be reused.

Additional equipment: Jar lifter (essential), canning funnel, bubble remover/headspace tool, clean cloths.

Step-by-Step Pressure Canning Process

Prepare Jars

1. Inspect all jars for chips or cracks. Even a small nick on the jar rim prevents a seal.
2. Wash jars in hot soapy water. Rinse well.
3. Keep jars hot until filling — place in a dish of hot water or in a low oven (200°F). Cold jars contacting hot food can crack.
4. Never boil the lids — this damages the sealing compound. Heat in a small pot of hot (not boiling) water.

Prepare Food

Follow a tested recipe exactly. Cube sizes, liquid ratios, and hot vs. raw pack method matter for heat penetration and safety.

Raw pack (cold pack): Food is packed raw into jars and covered with boiling liquid. Food shrinks during processing.

Hot pack: Food is pre-cooked in boiling liquid, then packed hot. Denser pack, less shrinkage, often better quality.

Fill Jars

1. Use a canning funnel to fill jars to the correct headspace — the space between the food and the lid.
2. Headspace matters: Too little headspace and the food may boil up under the lid during processing, preventing a seal. Too much headspace and not enough vacuum forms.
3. Standard headspace for pressure canning: 1 inch for meats and beans, 1/2 inch for most vegetables.
4. Remove air bubbles by inserting a bubble remover or thin spatula and rotating around the inside of the jar.
5. Wipe jar rims with a clean, damp cloth. Any food on the rim prevents a seal.
6. Place flat lid on jar, apply screw band fingertip-tight (tighten to resistance, then back off 1/4 turn).

Load and Vent the Canner

1. Add 2-3 inches of hot water to the bottom of the pressure canner.
2. Load filled jars using a jar lifter. For most canners, jars can be stacked with a rack between layers.
3. Lock the lid in place.
4. Heat on high until steam flows steadily from the vent hole/petcock.
5. Vent for 10 minutes (continuous steady steam). This removes air from the canner — air inside the canner lowers the temperature at which pressure is reached.
6. After 10 minutes, close the petcock or put on the weighted gauge.

Bring to Pressure

1. Continue heating. For a dial-gauge canner, watch the gauge climb to the target pressure (see table below).
2. For a weighted-gauge canner, the weight begins rocking or jiggling when pressure is reached.
3. Start timing ONLY when the correct pressure is reached.

Process at Pressure

Maintain the correct pressure for the entire processing time. Adjust burner to hold pressure steady — not fluctuating wildly.

Weighted gauge: Weight should rock/jiggle approximately 1-4 times per minute. If it jiggles constantly, reduce heat slightly.

Dial gauge: Keep needle at exact pressure. Slight variation (±2 lbs) is acceptable.

If pressure drops below the target during processing: Bring back to pressure quickly and restart the full processing time from the beginning. Partial processing time does not count.

Depressurize

1. When processing is complete, turn off heat.
2. Let the canner depressurize naturally. Do not rush this step — rapid pressure change can break jar seals or cause liquid loss from jars.
3. For most canners: allow 30-45 minutes to drop to zero pressure.
4. Confirm zero pressure by: dial reads zero OR you can press the petcock without steam releasing.
5. Wait 10 more minutes after the gauge reads zero.
6. Open the lid away from you — steam may remain.

Remove and Check Jars

1. Use jar lifter to remove jars without tilting.
2. Place on a cloth-covered counter with 1-inch spaces between jars.
3. Do not press, adjust, or tilt jars — let them seal undisturbed for 12-24 hours.
4. Listen for the satisfying "pop" of sealing lids (within first 15 minutes usually).
5. After 12-24 hours, check seals: press center of lid. If it flexes, the seal failed — refrigerate and use within days.
6. Remove screw bands before storage (leaving them on traps moisture and may cause false seal appearance).

Processing Times and Pressures (USDA)

Altitude Adjustment Table

At higher altitudes, water boils at lower temperatures and pressure canners must be adjusted to compensate.

For dial-gauge canners:

| Altitude | Required Pressure (add to recipe pressure) | |---------|-------------------------------------------| | 0-2,000 ft | 11 lbs (standard) | | 2,001-4,000 ft | 12 lbs | | 4,001-6,000 ft | 13 lbs | | 6,001-8,000 ft | 14 lbs | | Above 8,000 ft | 15 lbs |

For weighted-gauge canners:

• 0-1,000 ft: Use 10 lb weight
• Above 1,000 ft: Use 15 lb weight

Vegetables — Pints (10 lbs pressure at sea level)

| Food | Raw Pack | Hot Pack | |------|---------|---------| | Carrots | 25 min | 25 min | | Green beans | 20 min | 20 min | | Corn (whole kernel) | 55 min | 55 min | | Potatoes, cubed | — | 35 min | | Tomatoes (as vegetable) | 25 min | 25 min | | Beets | — | 30 min | | Peas (shelled) | 40 min | 40 min |

For quarts, add 5-10 minutes (see USDA tables for exact times)

Meats — Pints (10 lbs pressure at sea level)

| Food | Method | Time | |------|--------|------| | Ground beef (browned) | Hot pack | 75 min | | Beef strips/chunks | Hot or raw pack | 75 min | | Chicken (bone-in) | Hot or raw | 75 min | | Chicken (boneless) | Hot or raw | 75 min | | Venison | Hot or raw | 75 min | | Fish — pint jars | Hot | 100 min | | Fish — half-pint jars | Hot | 100 min |

Quarts are 90 minutes for most meats. Use USDA NCHFP for your specific food.

What Not to Can Under Pressure

Never pressure can:

• Dairy (milk, butter, cream, cheese) — canning does not produce safe shelf-stable dairy
• Pasta or rice in canning liquid — becomes mushy and changes density affecting heat penetration
• Thickened sauces (flour, cornstarch) — the thickener prevents adequate heat penetration
• Purées of low-acid vegetables without tested recipes — density varies

Storage

Properly sealed pressure-canned food stored in a cool (50-70°F), dark, dry location is shelf-stable for 1-5 years. The USDA recommends using within 1 year for best quality, though safety typically extends well beyond that for properly sealed jars.

Store without screw bands. Label with contents and date. Inspect every jar before use.