Brown Rice Flour

The Original PF Tek Substrate

This is the carbohydrate that started home mycology. The PF Tek (Psilocybe Fanaticus Technique) published in 1992 by Robert "Billy" McPherson built an entire generation of growers around one simple recipe: brown rice flour, vermiculite and water, mixed inside half-pint jars and sterilised. Three decades later it is still the most reliable first technique for new cultivators — and brown rice flour remains the carbohydrate source that defines it.

What Makes Our Brown Rice Flour Different

• Certified organic — milled from European brown rice grown without synthetic pesticides or fertilisers.
• Whole-grain — full bran retained, not refined white rice flour. The bran fraction is what gives brown rice flour its mycology value.
• Finely milled — uniform particle size for consistent hydration and even mycelial colonisation.
• Single ingredient — no preservatives, no anti-caking agents, no rice-flour blends.
• Non-GMO — European cereal origin, documented supply chain.

Classic PF Tek Recipe

For one half-pint (240 ml) wide-mouth jar:

• 2 parts vermiculite (by volume) — about 120 ml
• 1 part brown rice flour — about 60 ml ≈ 17 g
• 1 part water — about 60 ml

Mix the dry ingredients first until uniform, then add water and stir until evenly moistened. The substrate should clump lightly when squeezed but release no free water. Load loosely into jars without packing, leave a 1 cm dry vermiculite layer on top, lid with tinfoil and pressure-cook at 121 °C / 15 PSI for 60 minutes.

Why Brown Rice Flour Works

Brown rice flour delivers the three things Psilocybe cubensis mycelium needs from a cake substrate:

• Slow-release carbohydrates — the starch granules dissolve gradually during colonisation, giving mycelium a long fuel runway instead of a sugar spike that would invite contaminants.
• Bran protein and lipids — full whole-grain flour retains the bran layer, contributing nitrogen and trace lipids that white rice flour lacks.
• Particle structure — when bound by water inside vermiculite, brown rice flour forms a porous matrix the mycelium can colonise three-dimensionally rather than just on the surface.

Best Applications

• PF Tek half-pint cakes — the classic application. Cakes are birthed after full colonisation, dunked, rolled in vermiculite and fruited in a Shotgun Fruiting Chamber.
• Liquid Culture nutrient — 1–2 g per 100 ml of distilled water as a carbohydrate source for liquid culture jars.
• Agar plate enrichment — added to malt extract agar (MEA) at 5 g/L to support faster mycelial growth and clearer colony differentiation.
• Grain spawn boost — 1–2 % added by weight to rye or millet grain before sterilisation can shorten colonisation time on stubborn isolates.

Choose Your Size

Two formats are available:

• 100 g bag — the standard PF Tek session portion. Enough for roughly 6 standard half-pint PF cakes. Compact, stackable, ideal for occasional cultivators or single-session use.
• 1 kg bulk bag — production-scale stock. Enough for roughly 60 PF cakes, or 500 L of liquid culture broth at 2 g/L, or hundreds of agar plates. The economical format for high-volume mycology benches.

Pick the size you need from the dropdown above. Same flour, same European mill, same organic certification — only the bag size differs.

Building the Full Stack

PF Tek cakes work best when the rest of the workflow is in place. If you would rather skip the cake stage entirely and move straight to bulk substrates, see our sterile grain spawn bags: Sterile Millet Spawn Bag for fast colonisation or our pre-mixed bulk substrate: Sterile CVG Substrate Mix . For perlite to load your Shotgun Fruiting Chamber after birthing PF cakes, see: Perlite Substrate .

Storage

Keep the bag sealed and store in a cool, dry place away from direct sunlight. Sealed shelf life is approximately 12 months from milling. Once opened, decant into a sealed container and use within 3 months for best mycology results — brown rice flour with retained bran does go slightly stale after extended air exposure, and stale flour gives weaker mycelial vigour.