Gather materials: agar powder, distilled water, light malt extract or potato dextrose, yeast extract optional, pressure cooker or autoclave, sterile Petri dishes or jars, measuring tools, heat-safe container, alcohol, gloves, and a still-air box or laminar flow hood
Choose a basic recipe: 20 g agar powder, 20 g malt extract, 1 g yeast extract optional, 1 liter distilled water
Measure the water into a heat-safe container
Add agar powder and nutrients to the water
Stir thoroughly until mixed
Heat the mixture while stirring until fully dissolved
Pour the medium into bottles or jars suitable for sterilization
Cap loosely or cover with foil
Sterilize in a pressure cooker at 15 psi for 20 to 30 minutes
Let the sterilized medium cool until warm but still liquid
Disinfect your work area and tools with alcohol
Pour the agar into sterile Petri dishes or sterile containers inside a clean workspace
Fill dishes only partway to avoid overflow
Allow the agar to cool and solidify
Store sealed plates upside down after solidifying
Use the plates for mushroom culture transfers under sterile conditions
Optional recipe variations: potato dextrose agar, malt extract agar, or plain nutrient agar
Optional additives: activated charcoal, antibiotics only if needed and appropriate, or pH adjusters if required
Label each plate with date and medium type
Keep unused plates sealed and refrigerated if storing for later use