Black Agar Recipe - Activated Charcoal

Recipe: Black Agar

What is Black Agar?

Black agar is a nutrient culture dyed with activated charcoal powder. Cultivators use black agar to easily observe mycelial growth. The contrast between the white mycelium and black nutrient medium is outstanding, especially when sectoring for genetics.

What is Activated Charcoal?

Activated charcoal is a porous black powder made of organic material such as hardwoods, coconuts, etc. It is processed at high temperatures to activate it which decreases the size of its pores. Food-grade activated charcoal is used for a variety of different purposes such as improving kidney function, acne prevention, whiting teeth, curing hangovers, and many more.

BBQ charcoal is a completely different material and is not activated and contains harmful chemicals that could kill the mycelium. DO NOT USE BBQ charcoal for black agar.

Does Black Agar Increase Growth Speeds?

From observation alone, black agar seems to enable faster growth of mycelium. However, this could be an optical illusion because of the strong contrast. More testing is needed to know for sure, but I tend to have better success with black agar than standard LMEA.

Black Agar Ingredients

Black agar is nearly identical to the standard LMEA recipe. The only difference is you'll need to add activated charcoal to the dry ingredients.

What type of Actived Charcoal should you use?

The activated charcoal acts as a dye so the finer the powder the better. Look for food-grade and never use charcoal for BBQ because of the harmful chemicals.

If you fail to plan, you plan to fail!

Be warned that activated charcoal is messy and it will get everywhere. Plan ahead by covering your work area with newspapers or some equivalent. Also, make sure you have a good storage container ready. Ultra-fine = Ultra-messy.

Making Black Agar

Black Agar Recipe

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

How Long Will it Take?

  • Preparation: 10 mins
  • Cook time: 45 mins

What Equipment Do You Need

  • Pressure cooker - Must be able to hold 15-PSI.
  • Glass container - It must have a lid with a gas exchange. I used Erlenmeyer flask with a vented screw-on cap.
  • Digital Scale - For measuring dry ingredients.
  • Funnel - A funnel is handy if adding ingredients to a narrow mouth container.
  • Measuring Cup - To measure boiling water.
  • Oven Gloves - To handle the hot mixture. Oven mits or a cloth will work, but the oven gloves offer more dexterity.
  • Thermometer Gun - Used to monitor the temperature of the agar mixture.
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
  1. Boiling Water

    Begin by boiling water.

    "The water will evaporate, so boil more than the needed amount. "

  2. Activated Charcoal for Black Agar
    Dry Ingrediants

    In an autoclave-safe glass container, add 5g of agar-agar, 7.5 g of light malt extract, and around 1 g of activated charcoal.

    "The activated charcoal acts as a dy so not much is needed."

  3. Measure boiling water

    Carefully measure 250ml of the boiling water and pour it into the glass container to combine with the dry ingredients.

    "250 ml = 1 Cup"

  4. Disolving Black Agar

    Place a filtered lid on the mixture, then shake or swirl the mixture until the dry ingredients begin dissolving.

    "The glass will be very hot so I suggest wearing an oven glove or something to protect your hands."

  5. Protect Lid with foil
    Protect Lid

    Use foil to cover the lid. This prevents moisture from entering that agar mixture.

    "It also adds extra protection from air-borne contaminants when removing it from the pressure cooker."

  6. 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 cook until the pressure cooker reaches 15-PSI.

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

    Walk-Through: Pressure Cooker
  7. Pressure cooker 15PSI
    Cook at 15-PSI

    Cook the agar for 45-minutes after the pressure cooker reaches 15-PSI.

    "Liquid sterlizes faster than solids, but it is perfectly safe to cook agar longer than 45-minutes if sterilizing other things."

  8. 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."

  9. Monitor Temperature
    Monitor Temperature

    The agar is ready to pour once it reaches a temp between 116-122°F (46-50°C).

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

  10. 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.

Suggested Equipment