PF Tek Complete Guide — AI-Assisted

The PF Tek Substrate Recipe: Getting the Ratio Right

The substrate formula for PF Tek is precisely 2 parts vermiculite, 1 part brown rice flour (BRF), and 1 part water, measured by volume. For half-pint (250 mL) mason jars, this works out to approximately 140 mL vermiculite, 70 mL BRF, and 70 mL water per jar. The critical factor is moisture content — the substrate should feel like a wrung-out sponge when squeezed. If water drips freely when you squeeze a handful, it is too wet and will invite bacterial contamination. If it does not hold together when squeezed, it is too dry and mycelium will stall. Mix the vermiculite and water first, then add the BRF and mix until uniform. Fill jars loosely to within 1 cm of the rim (do not pack), then add a dry vermiculite layer on top as a contamination barrier. Wipe the jar rim clean, apply the lid (loosely), and cover the top with aluminium foil.

Sterilization Without a Pressure Cooker

PF Tek was specifically designed to work without a pressure cooker, using fractional sterilization (also called tyndallization). Place a rack or folded towel at the bottom of a large pot, add water to the level of the rack, arrange your foil-covered jars on the rack (the water should not touch the jars — you are steaming, not boiling), and bring to a rolling boil. Maintain steady steam with the lid on for 90 minutes. Let the jars cool completely in the pot — this takes 8-12 hours, so most growers sterilize in the evening and inoculate the next morning. With a pressure cooker, sterilize at 15 PSI for 60 minutes. The advantage of pressure sterilization is more complete elimination of heat-resistant endospores, but steam sterilization works well for BRF substrate because the low nutrition level of the substrate does not support aggressive contamination the way supplemented substrates do.

Inoculation Technique: Still Air Box Procedure

Inoculation is the most contamination-sensitive step in PF Tek. Set up your still air box (a clear plastic tote, ideally 60-90 litres, with two arm holes cut in the side). Wipe the interior with 70% isopropyl alcohol. Place your cooled jars, spawn syringe (liquid culture or spore syringe), lighter, and alcohol inside the box. Wait 10 minutes for air currents to settle. Flame-sterilize the syringe needle until red-hot, let it cool for 10 seconds. Inject approximately 1 mL of solution per jar, divided among 4 injection points around the jar perimeter, pushing the needle through the foil and lid. Replace the foil after injecting. Each syringe (typically 10-12 mL) can inoculate 10-12 jars. Work slowly and deliberately — rushed inoculation is sloppy inoculation, and a single contaminated jar produces spores that threaten your entire batch.

Colonization: What to Watch For Over 3-5 Weeks

After inoculation, place jars in a warm, dark location at 24-27 degrees Celsius. Within 3-7 days, you should see small white spots of mycelium growth at the injection points. Over the following 2-4 weeks, the white mycelium will spread through the substrate until the entire jar is colonized. Healthy mycelium is bright white, ropy or fluffy in texture, and has a faintly sweet, mushroomy smell. Warning signs during colonization: green, black, or orange spots indicate mould contamination — remove the jar immediately and dispose of it sealed. Wet, shiny, or slimy spots suggest bacterial contamination. Yellow or amber metabolites (liquid droplets) on the mycelium surface are normal stress responses and not necessarily contamination. Do not open jars during colonization — visual inspection through the glass is sufficient. Full colonization typically takes 21-35 days depending on temperature and species.

Birthing, Dunking, and Rolling: Preparing Cakes for Fruiting

Once a jar is 100% colonized (solid white throughout), wait an additional 5-7 days for the internal mycelium to consolidate — this 'consolidation period' strengthens the cake and improves fruiting performance. Then birth the cake: remove the lid and dry vermiculite layer, and gently tap or roll the jar until the cake slides out. The cake should be firm, white, and hold together as a solid cylinder. Immediately submerge the cake in cold water (tap water is fine) for 12-24 hours — this rehydrates the substrate and simulates a natural rainfall trigger for fruiting. After soaking, drain the cake and roll it in dry vermiculite until the entire surface is coated. The vermiculite coating maintains surface moisture, creates a microclimate for pin formation, and provides a barrier against contamination. Place the coated cake on a small piece of aluminium foil in your fruiting chamber.

Building and Managing a Shotgun Fruiting Chamber

The standard PF Tek fruiting chamber is a Shotgun Fruiting Chamber (SGFC): a large clear tote (60-110 litres) with 6 mm holes drilled on all six sides (including the bottom and lid), spaced approximately 5 cm apart in a grid pattern. Fill the bottom with a 10 cm layer of wet perlite — perlite absorbs water and releases it as humidity, maintaining 85-95% RH passively. Place your cakes on small squares of aluminium foil on top of the perlite, spaced 5-8 cm apart. The drilled holes provide passive air exchange driven by convection. Elevate the SGFC 2-3 cm above the surface on bottle caps or small blocks to allow air intake through the bottom holes. Mist the walls and perlite (not the cakes directly) 3-4 times per day, and fan the chamber with the lid for 30 seconds after each misting. Provide 12 hours of indirect light per day (a room light or LED strip is sufficient — no direct sunlight).

Fruiting, Harvesting, and Subsequent Flushes

Pins (tiny mushroom primordia) typically appear 5-14 days after cakes are placed in the fruiting chamber. They look like small white bumps emerging from the vermiculite coating. Over the next 5-10 days, pins develop into full-sized mushrooms. Harvest when the cap edges begin to flatten or slightly curl upward — for oyster mushrooms, when the cap edges thin and begin to wavy; for other species, just before the veil beneath the cap tears. Twist and pull the mushroom from the cake with a gentle rocking motion, or cut at the base with a clean knife. After the first harvest (first flush), soak the cakes again for 12-24 hours in cold water, return to the fruiting chamber, and repeat. Most PF Tek cakes produce 2-4 flushes over 4-8 weeks, with each subsequent flush producing fewer and smaller mushrooms. Total yield per half-pint cake is typically 7-15 grams dry weight.

Common PF Tek Problems and Solutions

Stalled colonization at 60-80%: Usually a temperature or moisture issue. Check that incubation temperature is 24-27 degrees Celsius (not cooler). The last 20% often takes longer because the mycelium has consumed the easily accessible nutrients near the injection points. Wait 7-10 more days before worrying. No pins after 10 days in fruiting: Check surface conditions (look for thousands of tiny water droplets under flashlight — like dew on grass), humidity (must be 85-95%), fresh air exchange (fan more aggressively if CO2 is high), and light (12 hours per day minimum). Elongated stems with tiny caps: Classic CO2 problem — increase fresh air exchange. Fan the chamber more frequently or drill additional holes. Aborted pins (small pins that stop growing and turn dark): Usually caused by humidity drops or temperature fluctuations. Stabilize conditions and future pins should develop normally. Green mould on cakes during fruiting: The cake is contaminated — remove it immediately. This usually means the cake was birthed before full colonization or the fruiting chamber humidity is too low.