Activated charcoal is a deeply dark powder made from organic materials such as hardwoods, coconut husks, etc. When added to media it provides a dark stain to the media allowing for excellent observability of mycellium. Some darker contamination can be harder to see at early stages however.
Additionally, there is some evidence that activated charcoal inhibits bacterial growth, so charcoal agar plates are a good media for starting spores on, as hopefully the mycellium will advance before the bacteria and it will increase the chance of making clean transfers.
Activated charcoal can be added at a rate of about 1g to 500ml.
Follow your recipe process and incorporate the activated charcoal along with your dry ingredients before sterilization.
- Don't use grilling charcoal, it's not the same!
- Powdered activated charcoal is very messy, work slow and seal your storage container well.