The freshly pulped parchment is fermented in concrete tanks for 18-24hrs, with or without added water, to remove the outer mucilaginous layer. Bacteria and fungi decompose the mucilage to a soluble material which is readily washed off with water. The resulting acidity can degrade the concrete lining of the fermentation tanks over time, requiring periodic maintenance.

The degree of fermentation is tested by feeling the temperature and consistency of the parchment with one’s hand, and by manually washing a few beans to make sure all the mucilage comes away properly. The fermentation tanks can be covered with a lid to increase the fermentation temperature.

The fermentation stage is crucial to the final cup quality of the coffee beans.

The next stage of processing is washing the fermented parchment coffee.