Making agar is easy; only takes 5 minutes but sterilization takes longer mostly because of the time it takes to heat up the water. I have made a few modifications to my PC that I would like to point out. Since PCs are designed for canning in mind they tend to be tall which is great for doing many jars of grain but here we are only steam sterilizing small squares. Raising up the plates inside the pc by placing something underneath will help keep them from floating around in the water. It is recommended that my 23q Presto be filled with 12 cups of water for steaming but if I fill that up without raising the base rack up the mini squares will tread water & float around. I use a round piece of metal rabbit fence under the stainless steel rack to raise it. Keeps the plates just above the waterline.
Also adding weight to the pressure float will help it stay more stable and make less noise. I taped 3 quarters to this one...just enough to keep it from dancing around too much when at full pressure. As you can see my PC barely fits under the hood....
So place your agar plates inside, spin the lid on tight, and turn the heat on full. Take the pressure weight off and wait for pressure to rise. Steam will begin to come out of the hole where the weight hangs and the pop up valve will pop up when under pressure. Keep waiting for the pressure to rise....
When the pop up valve is up you can place the weight back on. Pressure will continue to build but don’t start your timer just yet; wait for full pressure....
When the needle is this far right and stable you can begin a one hour timer. For grains I suggest to do 90 mins but for small agar plates an hour is plenty. You may need to back off the heat slightly to prevent redline.
After 60 mins turn off the heat. Let the PC cool overnight or until completely cooled 12 hrs later. NEVER try to open a hot PC. I leave everything inside the pc until I’m ready to innoculate which is the next step of this process. Everything inside will be sterile until the pc is opened. Stay tuned...