The Giling Basah processing method

Sumatra is a beautiful place to grow coffee but not such an easy place to dry coffee, which is why the locals devised Giling Basah – a unique coffee processing method.


The Gayo Highlands encircle Lake Tawar in Aceh, the northernmost province of Sumatra, home of our April 2016 Bean of the Month.

It’s hot and humid up in the mountains, which are covered in lush rainforest and dotted with natural hot springs – relics of the volcanoes which formed the island.

It’s a beautiful place to grow coffee. The combination of high altitudes and nutrient-rich volcanic soil provide an ideal climate for Coffea Arabica to flourish.

It’s not such an easy place to dry coffee. The ever-present humidity means that growers are unable to leave the beans out on patios for the days required to complete the usual washed or natural process. If left to sit for extended periods, the beans would simply go mouldy.

So, out of necessity, the locals have devised Giling Basah – a method unique to Sumatra which creates a unique flavour profile which has become the signature of Indonesian coffees.

Giling Basah translates to ‘wet hulled’. The process is:

  • Farmers pick the ripe red coffee cherries by hand. This is a vital step in quality control, as the unripe cherries could taint an entire batch with their sourness.
  • Once the cherries have been harvested, they are placed in barrels of water. If a cherry floats, it is defective and discarded, strained off the top. Defects are often the result of insects which bore into the fruit and damage the bean.
  • The wet cherries are then pulped – put through a hand cranked machine which removes the bean from the cherry. These machines are often home made, assembled from scrap metal, wood and bicycle parts.

At the end of this process, the pulp of the cherry is still attached to the bean. It is in this sticky state that the beans are packed into woven bags to ferment overnight. Fermentation is the key to the heavy body and low acidity of Indonesian coffees.

The overnight fermentation loosens the fruit pulp and in the morning the grower washes the beans by hand to remove any remaining fruit before drying the beans as best they can, down to between 50% and 30% moisture.

The parchment is then removed before the green beans are fully dried and the bean is ready to be sent to town to be dried fully.

Exposing the green bean to the air before it is fully dried creates the earthiness we expect from Sumatran coffees.

The Lake Tawar Hands of Hope coffee undergoes one further step. Each hessian sack which the green coffee beans are packed into comes through a foster home, where is is decorated with the hand prints of the children who live there.

The growers dedicate a portion of their profits from the coffee sale to these foster homes to improve the lives of the orphan children who live there.

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