Calculate accurate sterilization times for jars, bags, and substrate materials. Ensure complete sterilization with proper PSI and time calculations.
Regular boiling reaches only 212°F (100°C), which cannot kill resistant bacterial endospores. A pressure cooker at 15 PSI reaches 250°F (121°C), the temperature needed for complete sterilization that destroys all microbial life including heat-resistant spores. This is essential for grain spawn, agar, and liquid culture preparation.
Pressure directly affects sterilization temperature and time:
Container size significantly affects sterilization time at 15 PSI:
Half-pint to pint jars: 45-75 minutes. Ideal for spawn and agar.
Quart jars: 90-120 minutes. Most common for grain spawn production.
Spawn bags: 120-180 minutes. For bulk spawn production.
Absolutely not! Opening the PC during sterilization breaks the sterile environment and allows contamination. You must complete the full sterilization time and allow pressure to drop naturally. Never force cool or open early.
Test your gauge annually using a boiling water test or have it professionally calibrated. Inaccurate gauges can lead to under-sterilization and contamination. If your gauge reads incorrectly, add extra time or replace it.
Common causes: insufficient sterilization time, pressure cooker not reaching full pressure, contaminated inoculation technique, or compromised jar seals. Verify your PC reaches 15 PSI and maintain it for the full duration. Check jar seals before sterilizing.
Yes, but use the longest required time. If sterilizing agar plates (20 min) with quart jars (90 min), run for 90 minutes. The agar won't be harmed by extra time. Never use shorter times to accommodate faster-sterilizing materials.
You can still sterilize at lower pressures, but must increase time significantly. At 10 PSI, add 50% more time. At 12 PSI, add 25% more time. However, 15 PSI is strongly recommended for reliable sterilization.
Wait until jars reach room temperature (70-75°F). This typically takes 4-8 hours. Inoculating into hot substrate will kill your culture. Some growers wait overnight to ensure complete cooling.
Yes! Always add 2-3 inches of water to the bottom before each use. Running a PC dry can damage it permanently. Check water level if sterilizing for extended periods (2+ hours).