If you’ve ever wondered why Indonesian coffees, like Sumatra or Java, have such unique flavors, there’s an interesting process behind their profiles. The way the coffee beans are processed create the notes that are signature of this multi-island nation.

The neighboring villages of Mount Kerinci in the Sumatra region of Indonesia. Photo courtesy of Socii Coffee.

There are several coffee growing regions throughout the volcanic and lush islands of Indonesia with different altitudes, harvest seasons, and varieties. Some of the more well-known regions include Java, Sulawesi, and Sumatra. But each region uses the special way of processing coffee beans called the wet-hulled process. This technique is also known as a semi-washed process and commonly referred to as giling basah, meaning milled wet in Indonesian.

Sumatran coffee farmers. Photo courtesy of Socii Coffee.

Essentially, this process blends some of the characteristics of a fully washed process and a natural process to create a hybrid method of treating the coffee beans. In giling basah, coffee cherries are picked during the harvest season and sorted for ripeness. After sorting, the coffee skin and most of the fruit flesh from each cherry is removed using a machine called a depulper. Coffee is then laid out to dry to reduce its moisture content to a range between 20% and 35%, beginning the distinctive process that is the wet-hulled method.

This semi-drying portion is what makes the process so unique.

Indonesian wet-hulled vs Honduran fully washed. Photo courtesy of Purefi Coffee Roasters.

Most coffees are dried only once to a moisture content between 10% and 12%. And these are relatively warm coffee-growing regions along the Equator. But Indonesia is extremely humid and has heavy rainfall compared to other coffee-growing areas. So, in response to the region’s climate and in attempts to quicken the drying time, Indonesian coffees are dried up to three times less than the usual amount during its first drying phase. This technique was created conceptually to speed up the processing time and historically to secure profitable harvests for the Dutch East India Company, who began exporting the Indonesian coffees in 1711.

After drying to this 20 to 35 percentile moisture content, the parchment is removed from the beans using another machine called a huller. And the coffee beans are then dried again for a second time down to a more effective moisture content to minimize rotting. This double duty drying process develops a deep green color on the beans, ranging from the jaded greens of celadon glazed pottery to the drab greens of the olive branch.

The second drying also creates the region’s signature coffee notes. Indonesian coffees, like the Kerinci Sumatra, are earthy and spicy, with medium to heavy body and low acidity. Additional flavor profiles can range from cloves and leather to tobacco and cacao. Due to the wet-hulled process, these coffees pose unparalled individuality and present rare tasting notes not found in others.

If you’re interested in learning more about our Indonesian coffee, the Kerinci Sumatra, check out our tasting notes on our menu, and if you’re in the Greater Houston area, order a bag perfectly ground to your preference to be delivered to your doorstep through Drop.


  1. James Hoffman. “Processing.” The World Atlas of Coffee:  From Beans to Brewing – Coffees Explored, Explained and Enjoyed. Firefly Books, 2014.
  2. James Hoffman. “Indonesia.” The World Atlas Coffee:  From Beans to Brewing – Coffees Explored, Explained and Enjoyed. Firefly Books, 2014.
  3. R. Lynch. “Indonesian Wet Hulled Coffee:  Your One-Stop Guide.” The Perfect Daily Grind, October 21, 2015.