The wet-hulled process, sometimes referred to as semi-wash, is a hybrid coffee method used in parts of Indonesia, especially Sumatra. It results in a dark, opal-green coffee with little silverskin clinging to it, and a particular low-acid, earthy, heavy body flavor profile.
In this method, the farmer picks ripe coffee cherry, pulps off the skin and either dries it immediately for one day, or lets it sit overnight in a bucket (with our without water), then washes it the next day and dries it.
In either case, the coffee is partially dried with some or all of the mucilage clinging to the parchment-covered seed. It is then dried to 25-30% water content, and run through a wet-hull machine. Friction strips off the parchment, and the bean emerges swollen and whitish-green.
Then it is dried on the patio down to 11-14% moisture, ready for sorting, grading, bagging and export (explanation from http://www.coffeeshrub.com)