Black Agar Recipe
Mycelium on Black Agar

What is Black Agar?

Black Agar is a variation of Light Malt Extract Agar (LMEA) used in mushroom cultivation. It's made by adding activated charcoal powder to the traditional LMEA mix, resulting in a darker, black growth medium. This medium is often preferred by cultivators, like me, who have noted stronger and faster growth when using black agar. However, these observations are currently anecdotal and further research is needed to confirm this hypothesis.

Black Agar is sometimes referred to as Charcoal Agar, Dark Agar, or Activated Charcoal Agar.

Benefits of Black Agar

Black Agar presents potential advantages in mushroom cultivation, including:

  • Visibility: The contrast between the black agar and the white mycelium can make growth easier to monitor.
  • Strength & Speed: Some cultivators, myself included, have noticed seemingly stronger and faster mycelial growth on black agar, possibly due to the porous nature of activated charcoal allowing for increased surface area for the mycelium to colonize.
  • Reduced Contamination: Anecdotally, black agar appears to experience less contamination than traditional LMEA. The reason behind this is currently speculative but might be related to the presence of activated charcoal, which has known filtering and adsorption properties.
Ingredient Ratios
Water Agar LME A.Char Plates
250 ml 5 g 7.5 g ~1 g ~10
500 ml 10 g 15 g ~2 g ~20
750 ml 15 g 22.5 g ~3 g ~30
1000 ml 20 g 30 g ~4 g ~40
1250 ml 25 g 37.5 g ~5 g ~50
1500 ml 30 g 45 g ~6 g ~60
1750 ml 35 g 52.5 g ~7 g ~70
2000 ml 40 g 60 g ~8 g ~80

Step-by-Step Black Agar Preparation

The process for preparing Black Agar is similar to that of LMEA, with the addition of the activated charcoal powder.

In this walkthrough I make 250ml of black agar using activated charcoal.

How Long Will it Take?

  • Preparation: 10 mins
  • Cook time: 30 mins
  1. Dry Ingredients
    Dry Ingredients

    Use the digital scale to measure the dry ingredients (5g Agar-Agar, 7.5g LME, & ~1g activated charcoal powder) and add them to the container.

  2. Boiling Water
    Boiling Water

    Measure the boiled water (250ml) and pour it into the glass container.

  3. Disolving Black Agar

    Stir until the dry ingredients are completely dissolved.

    A magnetic stir can help ensure a thorough mix.

  4. Protect Lid with foil
    Protect Lid

    Secure a cap on the container and cover the top with foil to prevent steam from entering during pressure cooking.

  5. securely place the mixture in pressure cooker
    Pressure Cooker

    Prepare your and securely place the mixture inside a pressure cooker or autoclave. Seal the lid and begin cooking.

    "You can place empty jars around the agar mixture to prevent it from tipping over."

    How to use a Pressure Cooker
  6. Pressure cooker 15PSI
    Cook at 10-PSI

    Pressure cook the mixture for 30 minutes at 15 PSI.

    Be mindful of overcooking, as the sugars in the malt extract can undergo Maillard reactions with the amino acids, potentially affecting the medium.

  7. Depressurize Pressure cooker

    Once the time elapses, turn off the heat and allow the pressure cooker to return to zero PSI before cracking the lid open. When ready, remove the agar and place it in your work area.

    "Don't leave the agar in the pressure cooker for too long or else it will begin to solidify."

  8. Monitor Temperature
    Monitor Temperature

    Allow the mixture to cool to around 115-125°F (46-52°C) before pouring. Monitor the temperature with an infrared thermometer.

    Use a thermal gun to measure the temperature. Again, if it cools it will begin to solidify.

  9. Ready to Pour Agar
    Ready to Pour

    Now, you are ready to pour your mixture into petri dishes. You must follow the sterilization protocol for the next part. It is a good idea to prep while the agar mixture is cooking.

Tips for Success with Black Agar

Handling Activated Charcoal Powder

Activated charcoal powder is extremely fine and can create a mess if not handled properly. Here are some tips to manage it effectively:

  • Prepare your workspace: Activated charcoal can easily spread and stain surfaces. Lay down newspaper or a disposable tablecloth before handling the powder.
  • Transfer to a plastic container: The powder typically comes in a bag, which is a like cruel prank everytime you open it, as it can cause a cloud of thick black dust. Consider transferring the powder into a container for easier and safer storage.

Other Tips

As with LMEA, remember to pour your agar plates in a sterile environment and store them properly to minimize the risk of contamination. Experiment with different amounts of activated charcoal to determine what works best for your specific strains. Remember, while my observations and those of other cultivators suggest some advantages to using black agar, these remain largely anecdotal and further research is needed. Happy cultivating!

Please note that the ingredient ratios would remain the same as for LMEA with the addition of activated charcoal powder. The amount of activated charcoal can vary depending on your preference but a starting point could be 1 gram per 100 ml of water. Adjust as necessary based on your observations.
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