What's the Difference Between Double Washed, K72, Dry Fermentation Washed and Regular Washed?

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

With the gradual popularization of specialty coffee, more and more consumers are paying attention to the traceability information of single-origin coffees. Consequently, 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 washed processing?

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

Washed Method

Also known as the wet process, translated from "Wet Process," this is a method of obtaining coffee beans where the outer skin and pulp are removed before the seeds are dried.

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, or East Indian Process), which referred to traditional natural processing.

Before the 1850s, people processed coffee cherries using the most ancient natural drying method. It was only with the advent of the Industrial Revolution that this "skin-removing-first" coffee processing technology emerged. In the mid-19th century, Jamaica became one of the world's largest coffee-producing countries, producing approximately 70,000 tons of green beans annually. Due to its island climate, cherries were difficult to dry, making natural drying less favorable in this region.

In 1845, the invention of the world's first coffee pulping machine was patented by James Meacock from Kingston, Jamaica. This was a machine used to remove the outer skin of coffee cherries and could also sort coffee. Following this,越来越多的与咖啡去果皮机有关的发明相继诞生, and the washed method was formally applied to coffee production.

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

Double Washed

The original wet process involved washing the fermented coffee beans once with clean water to remove the pulp before sending 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 removed and washed again before being sent to the drying grounds for dehydration.

The reason Kenya initially changed conventional washing to "double immersion" was actually not for flavor pursuit, but due to insufficient local drying grounds. Kenya operates on a typical African cooperative model, where during harvest seasons, small farmers deliver fresh cherries to processing plants throughout the day. The pulping 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 tanks to let them "cool down" to avoid spoilage or contamination until the drying grounds became available.

This double-soaked washed form is called "Double Washed," and in producing regions, it's also known as "Fully Washed" or "Double Fermentation." Since Kenya was the earliest region where this processing method became popular, this type of washing is also called "Kenyan Process." Later, people discovered that this因地制宜而发酵两次的 washed coffee not only facilitated stable quality control in production but also brought rich layered fruity acidity to the coffee. Today, some coffee produced in American estates also adopts 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 ordinary washed and double washed methods.

This washing process emphasizes control of fermentation time. First, it undergoes 24 hours of washed fermentation, then the detached pulp is cleaned, followed by another 24 hours of fermentation in a clean water pool. Subsequently, residual components are cleaned again, introducing them into a tank with clean water for the final 24 hours of fermentation, totaling 72 hours. This process also imparts bright and clean high-quality fruity acidity to Kenyan coffee. The Assalia regularly offered by FrontStreet Coffee uses this washing technique, presenting acidity reminiscent of cherry tomatoes and dark plums in the brewed coffee.

Dry Fermentation (Washed) Method

Since the initial wet processing required large amounts of pure water, and the wastewater after fermentation has been acidified, discharging it into rivers or soil would cause environmental impact. Therefore, to respond to environmental concerns and save water resources, the more water-efficient dry fermentation washed method began to be advocated.

So-called "dry fermentation" involves pouring the parchment coffee with skin removed directly into fermentation tanks to sit still for about 6-8 hours. This step is actually very similar to the more familiar honey processing. The difference is that dry-fermented coffee still needs to be rinsed with water to completely remove the degraded and detached sticky substances. In terms of flavor, conventional washed coffee often has brighter taste characteristics, while dry-fermented washed coffee usually has rounder sweetness than wet-processed coffee (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 the washing method, the differences are mainly in the soaking duration and frequency during fermentation, high or low temperature, aerobic or anaerobic conditions, and whether additional substances are added.

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