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Agar is a nutrified, gel-like growth medium commonly used for the cultivation of bacteria and fungi. Often contained in petri dishes, this medium allows mycelium to be grown on a flat surface and offers great advantages by allowing the cultivator to clearly observe the growth of the mycelium, check for contaminants and select regions of the network for further expansion.

While cultivation on agar is less common in low-tech and home-scale setups, it remains the best method for acclimating strains to new substrates, isolating preferred growth characteristics and cleaning-up contaminated cultures.

The home-scale cultivator can successfully work with agar in a still air box (SAB), provided rigorous sanitation procedures are followed and precise techniques are practiced.

While single-use, plastic petri dishes are available and commonly used, we highly recommend investing in glass petri dishes (soda lime or borosilicate) to reduce unnecessary plastic production and wastage.

#Preparation Instructions

  • Weigh out the dry ingredients
  • Add water to the dry ingredients and mix well
  • Pour the agar solution into a glass container for sterilisation
    • A bottle with a narrow-neck works best because it makes pouring easier
  • Plug the container opening with a cotton ball and cover with aluminium foil
  • Load the container into a pressure cooker
  • Wrap glass petri dishes and tools (scalpel handle and / or inoculation loop) in foil and load them into the pressure cooker
  • Sterilise at 15 PSI for 20 minutes
  • Remove the lid of the pressure cooker just before complete depressurisation
  • Transfer the container, petri dishes and tools into a still air box (SAB)
  • Pour the agar solution into the petri dishes before it drops below 55°C
  • Stack the petri dishes into a column(s) after filling to reduce internal condensation
  • Optional: seal each petri dish with parafilm, label and store for future use or use them as soon as the agar has cooled and solidified


#Malt Extract Agar

  • Agar agar - 10 g
  • Dry, light malt extract - 10 g
  • Non-chlorinated water - 500 ml

#Potato Dextrose Agar

  • Agar agar - 10 g
  • Potato starch - 10 g
  • Dextrose - 7 g
  • Non-chlorinated water - 500 ml