Substance being scooped from bowl into another with colorful background

A Mycologist’s Guide to the PF Tek Method

A step-by-step guide to the classic indoor mushroom cultivation technique, PF Tek, including the necessary materials and potential pitfalls.

DoubleBlind Mag

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Disclaimer: this article covers a legal theme.

PF Tek is the classic indoor mushroom cultivation technique. It can be a little tricky to get the hang of, but it’s cheap as hell and uses things you can get from any grocery store or horticulture shop.

What is PF Tek?

Psylocybe Fanaticus, otherwise known as Robert McPherson, popularized and refined this technique, kicking off an entirely new style of indoor mushroom cultivation.

PF Tek vs. Monotub

Unlike monotubs, where colonized grain is mixed with bulk substrate, PF Tek only has a single step between inoculating and fruiting. The simple and quick process of PF Tek makes it perfect for beginners, but typically results in lower yields than monotubs. However, for those only wanting small doses, a few PF Tek jars might be all they need. 

READ: Spiderman Tek: A Grow Guide For Beginners

For those not ready to learn to make grain spawn, colonized PF Tek jars can also be crumbled into bulk substrate and used to create monotubs, so the two methods aren’t as mutually exclusive as they may first appear.   

How PF Tek Works

At its heart, PF Tek is really a brown rice substrate method, much like Spiderman Tek. However, the addition of vermiculite to the brown rice substrate retains moisture without turning the whole thing to mush. This stops the mycelium from forming one huge, dense, impenetrable mass, which is what happens when mushrooms are cultivated on grain alone. 

Your substrate is placed into jars with a layer of dry vermiculite to act as a filter, and topped with a lid or heavy-duty foil. These jars are then sterilized in a pressure cooker. When the jars are fully cooled, spores or liquid culture are injected through the foil (or pre-drilled holes in the lid) and the vermiculite layer straight into the substrate, where the mycelium begins to grow. The mycelium will eventually consolidate the substrate into a dense white mass forming what many growers call a “cake.” The cakes are encouraged to fruit by placing them into a “shotgun terrarium”—effectively a clear box with holes on all sides that’s filled with moist perlite. The increased fresh air and exposure to light encourages the cakes to pin, or to start forming primordia (baby mushrooms), and keeping a humid environment will make these mushrooms grow to their full potential.

Colonization Time 

Depending on your ambient temperature and inoculation method (i.e. spores or liquid culture), PF Tek cakes should take around two to four weeks to colonize. The time from inoculation to harvest should take around six to eight weeks.

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Fruiting Time

Once fully colonized and placed into a shotgun fruiting chamber, cakes will start to produce their first flush of mushrooms in a week or two, with subsequent flushes often coming in more quickly. The full process from inoculation to harvest should take around six to eight weeks.

Yield Estimates

Over the lifetime of each cake, most growers expect around 1¾ to 3½ oz (50 to 100 g) of fresh mushrooms, or around ⅕ to ⅖ oz (5 to 10 g) after drying.

READ: Why You Should Grow Your Own Mushrooms

Getting Started: PF Tek Materials 

You’ll need:

Table of Supplies

For the PF Tek jars:

  • ½-pint jars that flare slightly towards the opening 
  • Jar lids with hole punched in, or heavy duty foil with tape
  • Perlite
  • Brown rice flour (you can make your own with a coffee grinder)
  • Vermiculite 
  • Pressure cooker

For inoculation:

  • A still air box (or clean workspace)
  • Gloves
  • Paper towels
  • Micropore surgical tape (the medical tape you’d get from any store)
  • 70% isopropyl alcohol
  • A lighter or spirit burner (kept outside the still air box if using, to reduce fire risk)
  • Spore (or liquid culture) syringe

For the shotgun fruiting chamber:

  • Large plastic tub with lid, around 18 inches by 14 inches by 10 inches (45 cm by 35 by 25 cm) or above
  • Drill and ¼-inch (6 mm) drill bit
  • Perlite
  • Spray bottle

Best Jars 

The original PF Tek instructions cite Kerr half-pint wide mouth canning jars as preferable for use, but we mostly use half-pint (250 mL) preserve jars with foil on top instead. When selecting a jar, look for something slightly tapered and stay away from anything with shoulders, where the top of the jar is narrower than the body, as this will make it hard to remove the resulting cake.

Best Substrate

One jar/cake:

  • 120 mL vermiculite
  • 60 mL water
  • 60 mL brown rice flour
  • ¼ tsp instant coffee (optional)
  • ¼ tsp gypsum (optional)

When mixing your materials, be sure to mix the water and vermiculite before you add in everything else. This ensures that everything else sticks nicely to the wet vermiculite rather than just making one big wet mess.

PF Tek Recipe

To create the PF Tek cakes:

  1. Measure the vermiculite into a bowl.
    Substance from one bowl being scooped into another
  2. Add the instant coffee into the water.
  3. Stir to dissolve the coffee. 
  4. Add the coffee mixture into the vermiculite and stir to combine.
  5. Gradually add in the brown rice flour while stirring the mixture.
  6. Add in gypsum and stir to combine.Spoons stirring and pouring bowl
  7. Divide the mixture between your jars.Spoon inserting substance into jar
  8. With water, clean the edges of each jar so there are no channels for contaminants.
  9. Add a layer of the dried vermiculite to each jar.Spoon putting substance into three jars on table
  10. Wrap thick foil over the top of each jar. Make sure each jar is fully covered.
  11. Use tape to secure the foil around each jar.close up of jar with tin foil and tape
  12. Create a cross of tape across the top of each jar. This creates four injection sites and also keeps the foil in place.Birds eye view of jar with tape
  13. Place the jars into your pressure cooker, on a trivet so they don’t touch the bottom of the pressure cooker.3 Jars in Pressure cooker
  14. Sterilize for 30 minutes at 15 PSI/250 F (121 C), and they’re ready.

Don’t attempt to inoculate your jars before they’ve properly cooled down. Some people have success with inoculating PF Tek jars on their kitchen counter, but it’s more risky than a well-prepared bathroom or a still air box. 

Once your jars have cooled, sterilize the end of your needle by passing it through a flame; it should glow red for a second or two. If you are working inside a still air box, it’s best to do this step quickly outside the box to avoid accidentally melting the plastic. If you’re using 70% isopropyl alcohol, flame-sterilizing inside the box risks a serious fire.

When your needle is sterilized, shake the syringe up to disperse the spores throughout the liquid. Insert the needle near to where the tape meets the edge of the jar. Because of the way we’ve set the tape on top of the jars, there will be four very obvious and useful injection locations. 

You want to use around 2 mL of inoculant per jar, so when you’ve used around a quarter of this, remove the needle from the first injection point and move on to the second. Repeat this process until you’ve injected 2 mL into the jar through the four injection points.

Place your jars in a warm, dark place to colonize; between 70 F and 80 F (21 C and 27 C) is fine. Colonization should begin in a few days. Once the substrate inside your jar is fully colonized, including the bottom of the substrate, give it about another week before removing it from the jar. 

When your cakes are entirely colonized and pulling away from the sides of the jars, start preparing your fruiting chamber. Some growers choose to soak their PF Tek cakes in water for 12 to 24 hours before rolling in clean vermiculite. This helps add extra water to the cakes and promotes larger yields, but can be skipped if necessary. Most growers use a shotgun terrarium to fruit their PF Tek cakes, which is made by taking a large clear tub and drilling small holes, around 2 inches apart, on all six sides. This terrarium is then filled with a few inches of moist perlite for humidity, and set on legs (empty PF Tek jars are perfect for this) to increase airflow to all sides. 

Remove your cakes from their jars, and give them a quick rinse under the cold tap. Set them on small squares of foil to prevent the mycelium growing into the perlite. Place the terrarium not directly in front of a window, but perhaps next to a wall across the room or against the wall perpendicular to the window. White walls reflect light and help your mushrooms to grow.

Mist your terrarium with water several times a day. Spray the inside walls of the terrarium then gently waft the air to get rid of some of the CO2 and excess humidity. Pop the lid back on and leave them to do their thing.

Once your mushrooms are ready, gently take the cakes out of the terrarium and pull each mushroom off, one at a time. Place your thumb and forefinger right at the base of the mushroom and simply break it off with a little twist. You can bring your fully harvested cakes to a second flush by soaking them in clean tap water for another 12 to 24 hours. Once they’ve been soaked, you can pop them straight back into the terrarium and repeat the fruiting process.

Troubleshooting PF Tek

Despite being beginner friendly, no cultivation method is problem-free. So let’s spend a bit of time considering issues you might experience with PF Tek.


Due to their small size, contamination can quickly be detected in inoculated PF Tek cakes. Any bad smells (sourness, mustiness, etc.) or strange colors (green, pink, or black) should be treated as suspect. Additional moisture buildup, making the substrate look muddy, can be a sign of bacterial contamination. This shouldn’t be confused with condensation, which gathers on the inside of the glass and is typical of later stages of mycelial growth.

Any blue-ish tint on your cake will usually be a result of the cakes being handled and is perfectly normal. Throughout your grow, using a clean cotton swab, dab at anything that might look contaminated; if the color comes off onto the swab, it’s almost certainly contamination, but if it doesn’t, it’s likely bruising.

Not Colonizing

Jars might sometimes be slow to grow or stall out completely. The former situation is usually caused by a lack of heat. Seedling heating mats can be bought cheaply online as a way to boost your growing temperatures. Set your heat mat inside a small plastic tub and place something between the jars and the heat mat, like a clean chopping board or folded towel.

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If your grow stalls, it could be suffering from a lack of oxygen/gas exchange. A quick fix for stunted growth in PF Tek jars is to simply invert them at around 80% colonization for the rest of the incubation stage. This allows any buildup of CO2 to drain out more easily and should kick-start your growth. It’s important to keep the jars inverted until fully colonized.

This article is an extract from the expanded and updated second edition of best-selling The Psilocybin Mushroom Bible by Dr K Mandrake and Virginia Haze, forthcoming from Green Candy Press in May. 

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