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10 Steps on How to Make Mushroom Spawn Bags - Webster Mycology

Oh my... Spawn is surprisingly easy if you like repetitive work. Spawn can be made in so many different ways. I use whole oats and milo. So I am going to teach and show how I do my routine. I do one cook every day, and I follow these ten steps to the dot every time.

What I use from Start to Finish

- 50-pound bag of Whole oats

- 50-pound bag of Milo

- Unicorn T3 Bag

- Two 42ct All American Pressure Cooker

- 220v hot plates

- Timer

- 1 and 3 Liter measuring cup

- scale

- two 2' x 3' HEPA filters

Steps from start to finish

1. Grab your T3 bags and Your Oats and Milo

I pre-make hundreds of premade bags of my spawn with no water. For example, recently, my nephew and I grabbed six 50-pound bags of whole oats and six 50-pound bags of milo. We made all the bags. It was close to almost two hundred T3 bags. For this example, I will explain how to make Spawn from start to finish.

2. Measure out two and a half pounds of Milo and two and a half pounds of whole oats.

I use a pretty good scale that shows to the hundredth pound. I grab my 3-liter measuring cup and set it on the scale and zero it out. Then I use my 1-liter cup to measure two and a half pounds of each Milo and Whole oats. I put the whole mixture into a span bag. Two 42qt pressure cookers can fit six bags in each cooker. I set those still open to the side.

3. Add water and fold bags

For five pounds of a one-to-one mix of milo and whole oats, add 1 liter of water. I add to the twelve bags I have made. The one major tip I can say to keep things sterile and airtight is to fold along the seems and make sure the bags are tightly knit within themselves. I have seen it too many times that people don't take a little time and pride in their folds, and they come down with tons of contamination and ugly-looking bags.

4. Add spacers, false bottom, and water to the pressure cooker.

To sterilize your bags and build pressure inside the pressure cooker is to add spacers, water, and a false bottom to the pressure cookers. I use a simple 3-inch tall spacer and put four of them spread out in the bottom. Then I add the false bottom. Lastly, to complete this setup is to add 4 liters of water or just below the false bottom.

5. add bags to the pressure cooker and close the lid

How I organize and allow for expansion inside the pressure cooker I organize my bag in a triangle pattern—three on the bottom and three on top. Then to have some clarity, I had another false bottom on the top of all the bags. Close the lid and follow the directions on the specific cooker you have.

6. add a 15psi pressure weight to the cooker and turn it on

After the lids have been closed and everything is set in the pressure cookers and atop the Heating plate, add a 15psi pressure weight. Then turn the hot plates on high.

7. Reach 15psi and start a 3-hour timer. Watch and adjust as needed

Allow the cookers to reach 15psi or 250 degrees Fahrenheit and start a 3-hour timer. Check on the pressure cookers every once in a while and adjust the heat on the hot plate as needed. When My pressure cooker reaches the 15psi, I slowly adjust the dial down to medium heat, where it stays for the rest of the timer. Here where I am based is perfect for me. Different elevation means different settings. You have to play and test what works best for your elevation.

8. timer is up, and let them sit

When the timer is off, turn off the hotplates and let the cookers it until there is 0 pressure in the pressure cookers. It takes my pressure cookers about one hour to get to zero pressure.

9. Turn on Clean air filters

When my pressure cookers are around 5psi during the cooldown, I turn on my Hepa filters to filter and clean out the room even before the pressure cookers are finished.

10. you're finished with the cooking

When your Pressure cookers have 0psi, then you can open the lids. The spawn is still hot and will burn your hands. Grab some thick gloves so that the heat won't go through. Take the bags out one at a time and set them in front of the filters.

Those are the ten explained steps to make the spawn bags I use every day. I hope these steps allow you to grow your spawn production or even start your spawn production. To see more pictures and videos of all the processes I go through, check out my Facebook, Instagram, and youtube. The clickable links are listed below. If there are any further questions, please leave a comment or contact me through my social media. I will gladly answer any questions.


I realize that every other grower has their way of doing this same process, and it works for them. These are the steps I use and have been working for me since I started. Play with these steps and find what works for you and what will give you the best results. Everyone will have their way of making spawn.

A. Austin Webster


Webster Mycology

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