Grow mushrooms the EZ way.

How to Make PopCorn Grain Spawn (Popcorn Tek)


Popcorn tek is a simple spawn that a lot of beginners start with before moving on to other grains (although some people swear by it). It is a very easy spawn to create and most people have access to it. In this post I am going to walk through how to create it. There are a few techniques out there so do plenty of reading before deciding which method suits you.

The Cons of PopCorn Grain Spawn (Popcorn Tek).

  • Large kernel size (causing less inoculation jump-off points, this can be fixed by adding coffee grounds).
  • Cost.

The Pros of PopCorn Grain Spawn (Popcorn Tek).

  • Easy tek.
  • Easy to shake grains.
  • Widely available.
  • Low contamination rate.
  • Shorter pressure cook time.

How to Make Popcorn Grain Spawn.

Note: These steps will allow you to make 4-quart jars of popcorn grain spawn when completed. 


Pressure Cooker (my recommendations linked).

Large pot (you could use your pressure cooker as a pot).

PopCorn grain.

Quart Jars.

Tin Foil.

Gas exchange Lids (details can be found in this article here).

Elastic Bands.


Baking tray.

Prepare the Jars.

  • Pour grain into jars, fill each of the 4 jars halfway up.
  • Add water to the jar and leave for approximately 24 hours. This will allow time for any endospores on the outside of the grain to germinate before sterilisation (this step is optional but be warned you will have better results with this step).
  • Bring a pan of water to boil on the hob. There should be enough water to cover all the grains by an inch.
  • Pour the Popcorn into the boiling water. Then turn down the boil to a simmer.
  • Allow the Popcorn to sit inside the simmering pot for at least 45-60 minutes. Return to stir the pot every 5-10 minutes to keep any kernels from burning on the bottom of the pan. When the kernels are complete you should be able to split them in half no problem with your fingernail. This is done to hydrate the grains with water for the Mycelium to consume.
  • Pour out Popcorn Kernels into the colander and shake while the water evaporates off the outside. 
Boiling Popcorn grain
  • Spread Popcorn kernels out on a baking tray for 30 minutes (optionally this can be done by leaving them in the colander). We do this to allow most of the water on the outside of the grains to evaporate off.
  • Load popcorn into your jars distributing them evenly. You want to have a gap in the top of the jars DO NOT fill jars full to the top. As you wont be able to shake and breakup the grain.
  • Place lids on the Jars. Check this post here on my recommended lids for grain jars if you have never done this before.
  • Place tinfoil over the lids and secure with elastic bands.

Sterilize Jars.

  • Fill your pressure cooker up to the minimum requirement line (this is usually 2-3 pints of water for mine).
  • Place Jars inside the pressure cooker and secure the lid.
  • Heat the pressure cooker to 15psi.
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  • Turn down the heat but maintain the pressure at 15psi for 90 minutes
  • Once 90 minutes has passed, turn off the heat.
  • Allow the pressure cooker to cool overnight. This is important so that the Jars cool down before returning into the outside atmosphere, skipping this step can cause contamination/hydration issues.

Congratulations! You have now created popcorn grain spawn, next you can inoculate the grains with either liquid culture or colonized agar. To do that you are probably going to need a still air box so read about how to create one here. The rest of this post will be answering some commonly asked questions this tek.

Other FAQS

When to Shake Popcorn Tek?

When ⅔ of the grain jar is colonized is when I normally shake my grains. Always ensure there is space in the top of the jar when creating them to allow plenty of space for the grains to move around during a shake.

What does Fully Colonized Popcorn Grain Look Like?

Here are some photos of fully colonized popcorn grain spawn I have created previously.

Popcorn Spawn Colonization Time?

Colonization times are usually mushroom species/genetic dependent. However at least 14 days should be expected for the average grain prep.

Popcorn Tek vs Rye.

In my opinion Rye grain is the better grain between Popcorn and Rye. This is because the size of the grain kernels creates a larger number of inoculation jump-off points when you spawn to bulk. Alongside this Rye is very nutritious for Mycelium and can colonize it very fast. However, Rye does have its downfalls, I find Rye is more likely to contaminate, the grains are slightly harder to prepare and often harder to shake when the Mycelium expands.

Popcorn on the other hand is simple to create, easy to shake and has less contamination. It is also an easier grain to source. However, when you have a fully colonized jar of popcorn grain spawn you have less volume of Mycelium growth which can result in slower results after spawning to bulk.

In the end, it normally comes down to personal preference, a lot of commercial growers use Rye grain, however, I have seen a lot of very skilled amateurs use Popcorn grain. My advice is to try both and see which you prefer.

If you are interested in creating Rye grain checkout the discussion here.

Popcorn Spawn with Gypsum/Coffee.

If you are wondering when to add gypsum and coffee grounds to a grain jar I like to sprinkle them on during step 6, and also add a teaspoon to the inside of the before pressure cooking as well. 

Not only does adding gypsum and coffee to popcorn grain spawn increase nutrition, it also fills the gaps between the grains which means the mycelium has an easier route around the jars from grain to grain.

Can Popcorn Tek be No Soak?

Popcorn tek can be performed without a soak however it has mixed reception on the effectiveness. In theory Popcorn grain which is prepared for human consumption should carry a lower endospore load than something like Wheat Berry grain used for bird seed.

To perform a no soak tek follow the instructions described above however don’t perform a 24-hour soak before and leave the grain inside the pot to BOIL for 40 minutes during step 5.

How Long do you Pressure Cook Popcorn Grain Spawn?

Usually, this grain spawn is pressure cooked for 90 minutes as a minimum. This will allow the grains to be properly sterilized.

How do you Sterilize?

Place hydrated popcorn grain spawn inside a pressure cooker for at least 90 minutes.

Popcorn Spawn without Gypsum/Coffee.

This can be created without gypsum, the only difference is the mycelium will have to travel further without nutrition while jumping between popcorn grains. The tek discussed above was created without gypsum.

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