From Sweet Maria’s travelogues , here are a set of images of how coffee wet processing is performed.
Wet-processing is still the preferred way to take arabicaArabica refers to Coffea Arabica, the taxonomic species name of the genus responsible for around 75% of the worlds commercial coffee crop.: Arabica refers to Coffea Arabica, the... ...more coffee cherryOriginally coffee literature referred to the fruit of the tree as a "berry" but in time it became a cherry. It is of course neither. Nor is the... ...more from the fruit to the bean / seed. Why is that? Let’s look at the history a bit and talk about “natural” processingThe removal of the cherry and parchment from the coffee seed.: Coffee is either wet-processed (also called washed or wet-milled) or dry-processed (also called wild, natural or natural... ...more first.
Dry Process versus Wet Process
Traditionally dry-processing was used in areas with no access to water, or areas where less care was put into the coffee due to low value. Dry-processing required less infrastructure, and was technically easy.
It made sense in areas with extended collector systems, where coffee was gathered in very small amounts from many farmers, the good blended with the bad. It was typically a rusticA general characterization of pleasantly "natural" flavors, less sophisticated and less refined, but appealing. : What is Rustic? This is a general term we came up with... Dried... ...more process that resulted in a rustic tasting cup. It makes sense in that light that dry-process coffee is still called “natural coffee” too.
Dry processing has changed in some ways, and we now have top-grade dry processDry process coffee is a method for taking the fruit from the tree to an exportable green bean. The whole intact coffee cherry is dried in the sun... ...more coffee that requires careful effort to achieve a very intentional result. But in a sense this new wave of dry-processing
The Wet-Processing Advantage
Wet-processed coffee (also called washed coffee) was the traditional path to quality, for the very reason that it was more controlled and a better vehicle to achieve those intentional results: a uniform and clean tasting coffee.
Building a wet millThe wet mill is a processing center where coffee cherry from the tree is brought for initial processing.: The wet mill goes by many names (Beneficio, Factory, Washing... ...more was more of an undertaking: It required land for a central processing station, aka a washing stationIn Rwanda and some other East African countries, a wet mill is called a Washing Station.: In Rwanda and some other East African countries, a wet mill is... ...more, and access to a water source to run the mill and fermentAs an aroma or flavor in coffee, ferment is a defect taste, resulting from bad processing or other factors. Ferment is the sour, often vinegar-like, that results from... ...more the coffee. It required local infrastructure to get the coffee to the mill. It required skilled machine operators for the coffee pulper, and management to track the process. It required hired labor to perform the work, washing the coffee in the channel, delivering it to drying beds or patios etc.
One could make a good argument that the higher quality of good arabica coffee, it’s acidityAcidity is a positive flavor attribute in coffee, also referred to as brightness or liveliness. It adds a brilliance to the cup, whereas low acid coffees can seem... ...more and lower bitterness compared to robustaAteng is a common name for Catimor coffees widely planted in Sumatra and other Indonesia isles.: Ateng, with several subtypes, is a common name for Catimor coffees widely... ...more, could only be revealed with wet-process methods.
And that would be true, except that the care put into dry-processing now, and the costs to do it right, challenge the idea that fine coffee must be washed coffee
History of Coffee Process Systems
The kind of approach and investment, as well as centralization in the wet-process system harkens to colonialism in a sense. Or to the “hacienda” system that was usually owned by a nation’s elites, the landed class. Yet there was nothing intrinsically exploitative about the process. In fact, the systems that did the least to improve lives proved to be those resulting in low-grade commercial coffees, and those might be found more often in collector systems attached to natural coffee production.
As far as defining the process, the steps, the quality of the methods, you can find that repeated over and over in my travel videos, and other travelogues. I will leave it to the photos and captions to underscore the various approaches to creating a fine wet-process coffee! -Thompson
Wet-Process Coffee Method in Photos
The photo set roughly shows the process from coffee delivery and reception at the mill, sortingCoffee is sorted by size, density, and color in its preparation for export.: Sorting refers to several steps performed in the preparation of coffee for export. Coffee is... ...more cherryEither a flavor in the coffee, or referring to the fruit of the coffee tree, which somewhat resembles a red cherry.: Either a flavor in the coffee, or... ...more, pulpingThe first step in processing wet-process coffee, pulp natural or forced demucilage coffees. Pulping simply refers to removing the skins from the coffee fruit, leaving the parchment coffee... ...more off the skin, fermenting the coffee, washing it out of the fermentationFermentation in coffee processing traditionally referred to the stage in wet-processing of the coffee. We now understand that fermentation happens more broadly in nearly all processes, including honey... ...more tanks, initial sorting while wet, and while drying. All these steps aren’t done everywhere though… and I include a couple photos of pulpers that “machine wash” coffee so that it’s not fermentedAs a defect flavor, a fruit quality in a coffee that is excessively ripe, toward rotten. Fermented flavor can be the result of poor wet-processing, over-ripe cherry, or... ...more, like the PenagosPenagos Hermanos is a Colombian company that produces demucilage coffee processors. This is a forced demucilage machine that uses little water, and removes the coffee fruit layer from... ...more machines.
Farmers bring in their coffee cherry to the Mutovu station, a place we have soruced from for 8+ years 
And in fact, this is what they were doing … the women had just picked the coffee cherry and were showing it to Nasser. Yemen 
Qota Ethiopia- receiving coffee from coop members. It has traditional disc pulper which is cool; They have the three disc machine and 72 hour fermentation with 12 hours soaking. They take the good coffee from the floaters in lower grades and reprocess it sometimes to improve the quality. 
We arrive at Kibingo, another station we bought last year, at night. Cherry is coming in and being sorted by farmers in the evening – they have lights installed over the tables for presorting the cherry. Pre-sorting of coffee cherry at Montes de Oro MicroMill, San Pablo Tarrazu. Sweet Maria’s Coffee, Costa Rica This is a private washing station so there isn’t the extensive record keeping of the farmer-members as there would be at a cooperative. Nonetheless the payments to farmers bringing in and weighing their coffee cherry is carefully recorded. At this station the farmers are sorting out the green on ripe cherry from the ripe red cherry before they submit it for payment. Hopefully this will yield much better quality cup. You definitely should. Red cherry is prescreened just before it enters the pulper. India Bringing in coffee from the farms at night. Most coffee cherry is delivered late in the afternoon or early evening, and the coffee mills here can operate most of the night pulping the cherry into the fermentation tanks. Penagos 1500 with “fingers – rubber pads allow green cherry to pass unpulped 
Another method to wet-mill coffee avoids the entire fermentation process by forcing the pulp and mucilage off the coffee. This method protects the water supply, uses almost no water in the process, and seems to have great results in the cup! This is the Coffee de-pulper and de-mucilager at the wet-mill for Cafetalera Fernandez. A coffee pulper they can move around the farm to process ion the spot. Choluteca Honduras Nyamasheke coffee pulper – these are the traditional Kenya disc type John Gordon, old traditional pulping equipment from the British company. Pulpers are often in the house or on the back patio. Santiago Joven house with Brayan Joven Mihuti Factory of Rugi FCS, also in Mukurwe-ini area of Nyeri. freshly pulped coffee headed for the fermentation tank at Rosma mill Coffee coming from pulper at Fazenda IP, Carmo de Minas, Luis Paolo Dias Pereira 
Low grade coffee is pulped by farmers with a hand crank drum pulper – or used when the power is out. Quality wise, nothing wrong with hand-pulping. Its just a lot of work! Experiments at temperature controlled fermentation times in Antiquoia by Pedro. Fermenting coffee (dry ferment) with some skins of coffee fruit on top. They usually do 18-24 hours fermentation here. We ended up in Hambella for the night staying at a large washing station. It’s great to see the nighttime labor, so important in the cycle of the coffee washing station. Here the workers are wearing plastic ponchos and pieces of tarp as they unload coffee cherry from trucks. It is grueling work. And it goes on all night long. Fermenting coffee with some fruit skins on top. The usual Kenya method – 2 periods of fermentation for 24 hours each, then 12 hours soaking Dry fermentation in tiled tanks, with some residual fruit skins. Ocotal Nicaragua. In this warm climate fermentation can be as little as 8 hours. Tekele tests parchment to see if it is ready to wash in the channels and dry. This is submerged / underwater fermtation, which some call anaerobic. It’s typical in Sidama zone. Checking the coffee in the fermentation tank. They use submerged underwater fermentation here. The usual way to see if coffee is done is to feel for the sandpaper grit texture on a washed sample of parchment. Here they can quick check by seeing if the coffee sticks to the pole of the stirrer. Wet process coffee being fermented, improved by moving it during the process.India The new fermentation tanks – yet to be fully used. Mabingu Dalecho coop near duromina. 1993 m. – 36 hour fermentation plus 12 soak. 9 tanks. Long channel. Disc pulper. A very large coffee processing operation, and this season all the fermentation tanks are filled to the brim The washing channel is used to scrub the fermented mucilage from the coffee. It is also where coffee is graded by how heavy it is. The lower grade coffee floats in the washing channel and better coffee sinks. So the laborers are constantly pushing the coffee up against the flow of water and allowing lighter coffee to float past their rakes. It’s a primitive and effective system! Adding water to the fermentation tanks after the process is complete, to washe the coffee out so it can be taken to the drying beds. Haider Station Korea, Jimma Nkora is a historic station, said to be the first washing station in country. Before that coffee was home processed, which was usually just pulped and dried, not fermented. Here the laborers use their fet to work the already-fermented mucilage loose from the coffee parchment layer. The dance is a greeting for a visitor. I find it a little embarrassing honestly, but they don’t … so I try to respect that. Washing the coffee in the channel – scrubbing it with the “rakes” to release the fruity mucilage. Washing channel work is difficult. The whole team works in unison with the rakes slightly crossed over each other is they push the coffee up against the water current. Wet parchment coffee is heavy! I’ve tried to do this before and my arms get tired very quickly. Respect to those who do it all day, every day, during the coffee season. Shade drying or a skin drying is one of the great quality measures taken in the process of Coffee and Rwanda. We spent the night at the washing station of Mormora, and then moved on to see Taro in the morning. Was one of our favorite coffees from last year. Here the coffees being washed out from the fermentation tanks in the morning, to be scrubbed in the channel and sent to the soaking tank. The washing channel is both for scrubbing the coffee of any remaining mucilage still attached to the seed after fermentation, and also grading the coffee by density in the stream of water – Mordocofe Wet process coffee being sorted on the beds. They are sorting some of the bette qualities right out of the pulper since there are some defects you can sport easier when the parchment is wet. Fermenting in a small tub and Sorting coffee that was just pulped at Toyabungkah area of Batur, lake level is 1040 meters. House is 1100 meters. 
I Film image I took from a trip many years ago of coffee labor. Perhaps the amount of work put into Coffee as something that we have trouble acknowledging when we enjoy our cup On the raised beds they are Sorting coffee when wet and as it dries, Mutovu Coop Nyamesheke Rwanda Parchment coffee drying in the sun, after wet-processing fermentation. Here they dry on hot plastic tarps on the ground. Not ideal … too hot. Mboneramiryango coop – means “Light in the family”. Quality A-1 parchment on left, versus A-3 commercial quality yellowed parchment Our next visit was to Yukiro, a cooperative that always seems to be struggling, and yet produces some very fine coffee. Here the day workers are sorting the drying coffee on the tables. We’re hoping to get more consistency from this cooperative and see some improvements in in their practices. This includes the benefits to the day workers, the hand labor, as well as returning better benefits to the farmers. After all that’s what a cooperative is about: Sharing success. 1500-1600m, Gerardo is younger guy w good english, caturra 80%, catuai and villa sarchi, well managed farm, didnt cup outstanding Rusizi district, a Cooperative that has amazing practice is in quality. I was impressed with how carefully they work their crop. The light colored parchment is good clean wet-processed coffee, while the other is old poorly processed type 
Drying beds at the station – large scale. One of our first visits was to the washing station we purchased from last year. But we were a little miffed by the location. We were in the middle of Yirga Cheffe but the coffee was supposed to be from Gedeb, which is just on the southeast edge of the Yirg zone. It turns out this was the correct station, but because the license used for exports was labeled as Gedeb, that’s how it was sold. Oh well, the coffee was great and all the other details were correct. “Gedeb” became the running joke of the trip. Barokah cooperative. Sumatra – they use an indoor drying house for their washed coffees to ensure they don’t get re-wet by the afternoon storms here.
I hope there is something you noticed about many of these images. I hope you noticed all the labor that goes into quality coffee, how much work it takes, and how we wouldn’t have fine coffee without all those people selecting the fruit, removing defects, washing the coffee etc etc. ! -Thompson
Some related coffee articles of interest perhaps:
- Coffee Science – Green Coffee Science and Cup Quality
- Kenya Coffee Grades: Exploring the Coffee Grading System
- Green Coffee, Defined
- Green Coffee FAQ
- Product Guide: Roasted & Green Coffee Storage
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2 Responses
I would appreciate an article on who owns Sweet Maria’s, how they got into the business, and some history of the company.
Thanks for the other great articles.
Thanks for the suggestion Sam! While not in-depth, a lot of that is answered here. There are some very old photos from the early days there. Maybe it’s time to tack on a few more…
Glad you’re enjoying the articles on the site.
Best,
Dan