Tutorials/Basics/Sterile Technique

Most failed grows don't fail because of a bad recipe. They fail because something else got into the jar first. Mold spores and bacteria are everywhere: on your hands, in the air, on every surface in your kitchen. Mycelium grows slowly by comparison, so anything that sneaks into a nutrient-rich jar or plate will usually win the race.

Sterile technique is the set of habits that keep those passengers out during the moments your culture is exposed.

When it matters most

Clean technique matters any time you open sterile material to the air:

• Pouring and working with agar plates
• Inoculating liquid culture or grain jars
• Grain-to-grain transfers

It matters less when spawning to bulk substrate. By then your grain is fully colonized and the mycelium can defend itself. Clean hands and a wiped-down tub are enough.

Your workspace

Still air box (SAB)

A clear plastic tote turned upside down with two arm holes cut in the side. Its whole job is to stop air from moving. Spores drift on air currents, and still air lets them settle instead of landing in your jar.

• Use a tote around 60–100 qt. Cut two holes about 4–5 in. wide at a comfortable reach.
• Wipe the inside with 70% alcohol and let it sit a few minutes before working.
• Keep your arms moving slowly. Fast motion pumps air in and out of the arm holes.
• Work low in the box with jars and plates at the front, not under your arms.

Flow hood

A flow hood blows HEPA-filtered air across your work surface, so anything floating away from you is pushed off rather than settling. It makes agar work dramatically easier, but it is a significant purchase. Work downstream of the filter: nothing should sit between the filter face and whatever you have open.

The room

• Turn off forced-air heat, swamp coolers, and fans while you work.
• Avoid rooms with houseplants, pets, or open trash.
• A bathroom after running a hot shower is a classic option; the steam knocks airborne dust down.

Sanitizing

• 70% isopropyl alcohol kills more effectively than 91% or 99%. The water helps it penetrate cells, and it evaporates more slowly, giving it more contact time.
• Wipe jar lids, injection ports, syringe caps, and your gloves before working.
• Flame-sterilize needles and scalpels with a butane torch or alcohol lamp until the metal glows red, then let it cool a few seconds before touching culture. A hot blade will kill the tissue you're transferring.
• Wear nitrile gloves and spray them often. A clean shirt, tied-back hair, and a face mask help more than they seem like they should.

Habits

• Get everything into position before you open anything.
• Open things as briefly as possible, and never reach over an open plate or jar.
• Don't talk, cough, or breathe over open cultures.
• Label everything immediately: what it is, which transfer it came from, and the date.
• Keep a notebook. When something contaminates, your notes are how you figure out which step failed.