Use plain, untreated charcoal
Crush the charcoal into small pieces or powder
Rinse the charcoal with clean water to remove ash and dust
Dry the charcoal completely
Heat the charcoal in a covered metal container with limited airflow
Keep the container at high heat for a long period
Remove the container and let it cool completely
Mix the charcoal with a strong activating agent such as calcium chloride or potassium hydroxide
Soak the charcoal in the activating solution
Drain the excess solution
Heat the treated charcoal again at high temperature
Rinse the charcoal thoroughly with clean water until neutral
Dry the activated charcoal completely
Store the activated charcoal in an airtight container