PF Tek
6 to 10 weeks from inoculation to first harvest
The standard first method. Brown rice flour and vermiculite in half-pint jars, sterilised in a pressure cooker, colonised, then fruited as bare cakes. It is slow and low-yielding compared with grain-to-bulk, and it is forgiving of the mistakes beginners actually make, which is the trade it exists to offer.
What you need
- Half-pint wide-mouth canning jars with two-piece lids
- Vermiculite, medium or coarse grade
- Brown rice flour
- Water
- Pressure cooker (a stovetop 6 quart or larger)
- Spore syringe or liquid culture syringe, 10 ml
- 70% isopropyl alcohol
- Micropore tape
- A clear plastic storage box for a fruiting chamber
- Perlite
Procedure
- 01
Mix the substrate
Combine vermiculite and water first, then fold in the brown rice flour last. Mixing flour into dry vermiculite gives you clumps that never hydrate properly and colonise unevenly.
- Vermiculite
- 2 parts by volume
- Water
- 1 part by volume
- Brown rice flour
- 1 part by volume
- Target field capacity
- Squeeze hard: one or two drops, not a stream
Watch out: Too wet is the most common error and it is unrecoverable. Excess water pools at the jar bottom and turns anaerobic, which bacteria colonise long before mycelium reaches it.
- 02
Fill and cap the jars
Fill loosely to about 1.5 cm below the shoulder, do not pack it, mycelium needs air gaps to move through. Top with a 1 cm dry vermiculite barrier, which stops airborne contaminants reaching the substrate through the inoculation holes. Fit lids with four small holes around the rim, cover the lid with foil.
- Dry vermiculite cap
- 1 cm
- Inoculation holes
- 4, evenly spaced
- Headspace
- 1.5 cm
Watch out: Packing the substrate down slows colonisation by weeks and can stall it entirely.
- 03
Sterilise
Pressure cook the jars. Let the cooker vent steam for 10 minutes before sealing the weight, so that the chamber is steam rather than air, a cooker full of air does not reach the temperature its gauge claims. Cool to room temperature before opening, which takes several hours and cannot be rushed.
- Pressure
- 15 psi
- Time at pressure
- 60 minutes
- Cool-down
- 4+ hours, undisturbed, lid on
Watch out: Opening a hot cooker sucks unfiltered room air across warm substrate. Wait for genuinely cool jars.
- 04
Inoculate
Flame the syringe needle to glowing, let it cool a few seconds, wipe the foil with isopropyl, and inject through each hole down the inside of the glass so you can watch the colonisation front. Work in still air, a bathroom after a hot shower has settled dust and is better than a kitchen.
- Per jar
- 2 ml total, ~0.5 ml per hole
- Needle
- Flame to red between every jar
Watch out: A syringe of unknown provenance is the single largest contamination source in this method. Spores from a reputable vendor, or make liquid culture from a clean print.
- 05
Colonise
Incubate in the dark. Light is irrelevant to colonisation and warmth is not: a 6 °C difference roughly halves or doubles the time. Expect visible growth in 5 to 10 days and full colonisation in 3 to 5 weeks.
- Temperature
- 24–27 °C
- Light
- Not required
- Consolidation after full colonisation
- 7 days
Watch out: Above 30 °C you are incubating bacteria and Trichoderma preferentially. Heat mats without a thermostat routinely overshoot.
- 06
Birth and dunk
Once fully white and left a further week to consolidate, tip each cake out, roll in dry vermiculite, and submerge in cool water for 12 to 24 hours weighted down. This restores the water the cake will spend on fruiting.
- Dunk
- 12–24 hours in cool water
- Water temperature
- Below 20 °C
Watch out: Skipping the dunk gives a decent first flush and almost no second.
- 07
Fruit
Place the cakes on a perlite bed in a chamber with holes for gas exchange. Fan and mist several times daily. Pins appear in 5 to 12 days; harvest as the veil tears and before spores drop.
- Temperature
- 21–24 °C
- Humidity
- 90–95%
- Fresh air exchange
- Fan 3–5× daily, 30 seconds
- Light
- 12 hours indirect ambient, a directional cue, not photosynthesis
Watch out: Misting the cakes directly rather than the chamber walls causes bacterial blotch. Mist the perlite and the sides.
- 08
Repeat and dry
Re-dunk after each flush. Expect three or four flushes, each smaller. Dry until cracker-dry, bendy is not dry, and material that bends still holds enough water to degrade in storage.
- Flushes
- 3–4
- Drying
- Fan-dry 24h, then desiccant to cracker-dry
- Storage
- Airtight with desiccant, dark, cool
Troubleshooting
| What you see | What it is | What to do |
|---|---|---|
| Green patches, usually starting white then turning forest green | Trichoderma. Outcompetes mycelium and will take the jar. | Remove and dispose of the jar outside the growing area immediately. It is not recoverable, and opening it indoors seeds every other jar you own. |
| Grey-black fuzzy growth with visible pinheads | Cobweb mould (Dactylium). Grows visibly faster than mycelium and is grey rather than white. | Recoverable if caught early. Mist the patch directly with 3% hydrogen peroxide and increase fresh air exchange. Cobweb mould reflects too little air movement. |
| Slimy, wet, grey or yellow patches with a sour or foul smell | Bacterial contamination, almost always from substrate that was too wet. | Not recoverable. Dispose of it. Next batch, hit field capacity properly. |
| Yellow or amber droplets on healthy white mycelium | Metabolite exudate. Normal, and not contamination. | Nothing. Very heavy exudate suggests too little fresh air exchange. |
| Full colonisation but no pins after two weeks | Usually insufficient fresh air exchange, or the cake dried out. | Increase fanning frequency, verify humidity, and re-dunk. Carbon dioxide accumulation is the most common cause of a stalled chamber. |
| Long thin stems with tiny caps, growing toward one place | Carbon dioxide accumulation. The mushroom is reaching for air. | More fresh air exchange, and check the light is not coming from a single point at one side. |
| Nothing at all after three weeks | Dead syringe, temperature far too low, or failed sterilisation. | Check incubation temperature first. It is the usual answer. If jars are warm and clean but blank, the culture was not viable. |
Sources
- [1]Shroomery cultivation archives
- [2]Stamets & Chilton, The Mushroom Cultivator (1983)