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.
Black Agar presents potential advantages in mushroom cultivation, including:
| 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 |
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.
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.
Measure the boiled water (250ml) and pour it into the glass container.
Stir until the dry ingredients are completely dissolved.
A magnetic stir can help ensure a thorough mix.
Secure a cap on the container and cover the top with foil to prevent steam from entering during pressure cooking.
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
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.
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."
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.
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.
Activated charcoal powder is extremely fine and can create a mess if not handled properly. Here are some tips to manage it effectively:
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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