Introduction to Sterile Technique

Why Sterile Technique Matters

Mushroom cultivation is essentially a race between your desired mycelium and unwanted contaminants. Moulds, bacteria, and other fungi are everywhere in our environment - in the air, on surfaces, and on our skin. Without proper sterile technique, these competitors will outpace your mushroom culture.

The good news? With consistent practice of basic sterile techniques, you can achieve success rates of 90% or higher.

Understanding Contamination

Common Contaminants

• Trichoderma (green mould) - The most common enemy
• Cobweb mould - Fast-spreading, wispy grey growth
• Bacteria - Often shows as wet, slimy patches
• Black mould - Various species, easily recognisable
• Yeast - Creates off-smells and unusual textures

How Contamination Spreads

1. Airborne spores - Floating in every room
2. Surface contact - From hands, tools, surfaces
3. Unsterilised materials - Substrate, water, containers
4. Poor storage - Exposure to ambient conditions

Core Principles

1. Work Clean

Before any mycology work:

• Shower and wear clean, close-fitting clothes
• Tie back long hair
• Remove jewellery from hands and wrists
• Clean your workspace thoroughly
• Have all materials prepared and within reach

2. Minimise Air Movement

Still air is your friend:

• Close windows and doors
• Turn off fans and HVAC
• Work in a small, enclosed space
• Move slowly and deliberately
• Never work outdoors

3. Sanitise Everything

Isopropyl alcohol (70%) is your primary tool:

• Spray all surfaces before work
• Wipe down all containers and tools
• Clean hands frequently
• Spray the air in your workspace
• Keep alcohol spray within reach

4. Work Quickly but Carefully

Every second a container is open increases contamination risk:

• Prepare everything before opening
• Minimise time containers are unsealed
• Work efficiently without rushing
• Practice your movements beforehand

Essential Equipment

Must Have

• Still air box or laminar flow hood
• 70% isopropyl alcohol in spray bottle
• Pressure cooker (for substrate sterilisation)
• Nitrile gloves (non-powdered)
• Paper towels (lint-free if possible)
• Lighter or torch (for flame sterilisation)

Nice to Have

• Laminar flow hood (significant upgrade from SAB)
• HEPA air purifier for your workspace
• Dedicated cultivation clothes
• Surgical mask or N95 respirator

Building Good Habits

Before Every Session

1. Clean your entire workspace
2. Take a shower (or at minimum, wash hands to elbows)
3. Prepare all materials and place within reach
4. Spray down your SAB interior
5. Wait 5-10 minutes for air to settle

During Work

1. Keep movements slow and smooth
2. Never reach over open containers
3. Flame sterilise tools between uses
4. Spray hands after touching anything
5. Work from cleanest to least clean items

After Each Session

1. Clean all reusable tools
2. Dispose of contaminated materials properly
3. Note any issues in your cultivation log
4. Clean your workspace for next time

Common Mistakes

Mistake 1: Rushing

Taking shortcuts saves minutes but costs weeks when contamination strikes. Slow down.

Mistake 2: Working in Open Air

Even "clean" rooms have thousands of contaminant spores per cubic metre. Always use a SAB or flow hood.

Mistake 3: Skipping Hand Hygiene

Your hands are the #1 contamination vector. Wash thoroughly and spray with alcohol frequently.

Mistake 4: Not Testing Your Technique

Before inoculating expensive spawn, test your technique with agar plates. They'll reveal any problems quickly.

Next Steps

Ready to put these principles into practice? Learn how to build and use a still air box in our Still Air Box Basics guide.

For substrate preparation, see our Pressure Cooker Sterilisation guide.