How Exactly is Kenya's Double Washed Process Operated? What Changes Does Double Washed Processing Create?

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The washed method, one of the most traditional and common processing methods for coffee beans, not only significantly improves production quality through its dehulling and washing procedures but also imparts excellent clarity to the cup. It has become a favored bean processing method for countless coffee enthusiasts, including FrontStreet Coffee.

With the gradual popularization of specialty coffee, more consumers are beginning to pay attention to the traceability information of single-origin coffees. As a result, many producers have added prefix modifiers to processing method names to highlight certain selling points, such as "Double Washed," "K72 Washed," "Dry Fermentation Washed," and so on. So how do these differ from conventional washing?

Before understanding these "new-style" processing methods, FrontStreet Coffee believes it's necessary to first clarify the origins of traditional washing.

Washed Method

Also known as the wet process, translated from "Wet Process," this is a method of obtaining coffee beans by removing the outer skin and pulp before drying the seeds.

According to relevant materials reviewed by FrontStreet Coffee, this wet processing method originated in the West Indies in the nineteenth century and was developed in Jamaica, where it was called WIP (West Indian Process). It was mainly suitable for humid and rainy regions. In contrast, there was OIB (Oost Indische Bereiding), which referred to traditional natural processing.

Before the 1850s, people processed coffee cherries using the most ancient natural drying method. It wasn't until the Industrial Revolution that this "peel-first" coffee processing technology emerged. In the mid-19th century, Jamaica became one of the world's largest coffee-producing countries, producing about 70,000 tons of green beans annually. Due to its island climate, the cherries were not easy to dry, making natural drying less favorable in this region.

In 1845, the invention of the world's first coffee pulper machine was patented by James Meacock from Kingston, Jamaica. This was a mechanical device for removing the outer skin of coffee cherries and could also perform coffee screening. Following this, more and more inventions related to coffee pulpers emerged, and the washed method was formally applied to coffee production.

The process of traditional wet processing is not complicated: floating → depulping → fermentation → washing → drying → hulling → packaging. However, its implementation requires an adequate water supply, and because it relies heavily on mechanical assistance, producers using the washed method must also have sufficient funds to invest in equipment purchases. The rise of the washed method coincided with early American plantations built by capital—that is, those with sufficient operating funds, coupled with various inventions of pulpers/hullers that emerged to meet the demands of the times, which drove the widespread adoption of the washed method throughout the Americas.

Double Washed

The original wet process involved washing fermented coffee beans once with clean water to remove the pulp before transporting them directly to the drying grounds for drying and packaging. However, in Kenya, coffee that has been washed once is re-immersed in a pool of clean water, then taken out and washed again before being sent to the drying grounds for dehydration.

The reason Kenya initially changed conventional washing to "double soaking" was not actually to pursue flavor but was due to insufficient local drying space. Kenya operates on a typical African cooperative model. During harvest seasons, small farmers deliver fresh cherries to processing plants throughout the day. The depulping and fermentation process is relatively simple and not time-consuming, but drying each batch of fermented beans takes at least 5 to 7 days. Sometimes, when the volume to be processed is too large, there's no space to dry the washed beans. Therefore, people had to pour the wet beans back into the pools to let them "cool down" and prevent spoilage or contamination until the drying grounds were available.

This form of double-soak washing is called "Double Washed" and is also referred to as "Fully Washed" or "Double Fermentation" at origin. Since Kenya was the first region where this processing method became popular and implemented, this type of washing is also known as the "Kenyan Process."

Later, people discovered that this因地制宜 (adapted to local conditions) double-fermented washed coffee not only facilitated stable quality control in production but also brought richly layered fruit acidity to the coffee. For example, FrontStreet Coffee's Kenya Small Tomatoes uses double washing, often exhibiting rich cherry tomato and preserved plum aromas after brewing, with a very distinctive flavor. Today, some coffees produced by American estates also adopt this Kenyan-style washing.

K72 Washed Method

Also known as the Kenya 72-hour washed processing method, it can be understood as an additional extension of both regular washing and double washing.

This washing process emphasizes control over fermentation time. First, it involves 24 hours of washed fermentation, followed by cleaning off the degraded pulp. Then it ferments for another 24 hours in clean water pools, followed by another cleaning of residual components before introducing it into a tank with clean water for the final 24 hours of fermentation, totaling 72 hours. This process also imparts bright, clean, high-quality fruit acidity to Kenyan coffee. FrontStreet Coffee's daily offering, Assalia, uses precisely this washing technique, allowing the brewed coffee to present acidity reminiscent of small tomatoes and dark plums.

Dry Fermentation (Washed) Method

Since the original wet process required large amounts of pure water, and the wastewater after fermentation had been acidified, discharging it into rivers or soil would impact the ecological environment. Therefore, in response to environmental concerns and to save water resources, the more water-efficient dry fermentation washed method began to be advocated.

So-called "dry fermentation" involves directly pouring depulped coffee beans into fermentation tanks to sit for approximately 6-8 hours. This step is actually quite similar to the more familiar honey processing. The difference is that coffee after dry fermentation still needs to be rinsed with water to completely remove the degraded, fallen sticky substances. In terms of flavor, conventional washing often has a brighter taste, while dry fermentation washed coffee usually has a rounder sweetness than wet processing (because it's similar to honey processing).

It's not difficult to discover that fermentation is an essential step in washed processing. Therefore, regardless of which washing method is used, the differences are merely in the soaking duration and frequency during fermentation, high or low temperature, aerobic or anaerobic conditions, and whether additional substances are involved.

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