3: Processing


Welcome to the third edition of our blog where we will introduce you to processing methods, and catch up on all the latest news!

We are thrilled to have a guest feature as Steve Leighton of Hasbean takes us through coffee processing methods. Steve sources every single bean of coffee that we use, he doesn’t just know the farmers names – he knows their dogs names! The term “hands on” doesn’t do justice to Steve, he quite literally eats, sleeps and drinks coffee, and we couldn’t be happier to have him on board for this blog. More on that later.

Last Monday evening saw our very first “coffee at home” workshop. A free event, it was designed to help our customers achieve more consistency in their coffee making and improve their understanding of different brewing methods. We covered espresso, chemex, and Aeropress, drank stupid amounts of coffee, and had lots of fun. We will definitely run a similar event again soon. We are always delighted to help so please don’t hesitate to get in touch with any questions you have.

Another event in the pipeline for later in March is a tea tasting to coincide with the arrival of some phenomenal new teas from our friends at Waterloo Tea. We have now added Hibiscus Berry, Cranberry Fruits and Vanilla Black to our menu, all of which really are worth checking out.

Back on the subject of coffee, recently we introduced a weekly “single origin day”. Such was the success of the first day, it became “single origin half day”, as we sold out of Yirgacheffe at 2pm! Since then we’ve also had a Brazilian topazio from Fazenda Passeio, and a natural pacamara from Finca San Sebastián in Guatemala.

Due to their success, we’ve now decided to move towards having single origin coffee on bar all the time. The excellent Momentum blend from 3FE has served us really well since we opened our doors, but it feels like a natural progression now to make the move. As of this week, we plan to have a coffee on bar for three or four days and then change to a new one.

In our final piece of news, Neil is representing Arch Coffee in the Irish Aeropress Championship in Dublin next Saturday 14th. He’s one of 20 competitors in our first foray into coffee competition, and we look forward to telling all in our next blog.

And so back to Steve! Following on from our previous blogs which covered the origins of coffee & varieties, we’ll now delve into processing methods, and there’s no better man for the job. Steve, over to you!

PROCESSING by Steve Leighton

The coffee tree produces fleshy red fruit called a drupe, which is commonly referred to as the ‘berry’ or ‘cherry’. The coffee ‘bean’ is actually a seed which is encased within the cherry.

Raw coffee beans are light brown in colour with a distinct green hue which varies in depth. Consequently, unroasted beans are usually referred to as ‘greens’.

Speciality coffee picking tends to be undertaken by hand and good quality harvesting takes place when the cherry is at its ripest. This can mean many re-picks as only fruit that is fully ripe is selected in order to get the very best cup of coffee possible. In
contrast, lesser quality commercial grade commodity coffees are often strip picked, having everything taken from the plant at once for reasons of speed and labour economy. This can have a significant effect on the cup quality.

After the ripe fruit is harvested, the beans need to be removed from the cherry fruit and mucilage, then ‘hulled’, cleaned and sorted. This can be achieved in a number of ways


The fruit of the cherry is removed from the beans before they are dried. This is referred to either as the washed process or the wet process, and the resulting production is known as washed coffee.

The wet method lends itself to the efficient sorting and removal of poor quality beans. After harvest, the fruit is immersed in water and sorted. Whilst good ripe coffee sinks to the bottom of the tank, bad or unripe fruit, the ‘floaters and stinkers’ as they are
called, rise to the top and can be removed.

The whole cherry is then pushed in water through a milling screen that removes the flesh from the seed of the fruit, but this does not completely get rid of the slimy layer of mucilage, some of which remains on the beans.

The mucilage can be removed either by fermenting the beans in tanks before washing them in plenty of fresh water to remove any residue, or by the use of machinery employing a process of mechanical scrubbing.

The fermentation process is a very difficult thing to get right; if left too long the beans could have a nasty ferment taste to them, or not long enough and too much of the mucilage might remain on the bean, which would have an equally negative impact on the coffee.

Conversely, fermentation that is carried out correctly can have some very positive effects on the quality of the resulting coffee by virtue of the process itself.

Mechanical scrubbing has a far more predictable end result, though removing the fermentation stage and prematurely separating the fruit residue from the bean does take away a valuable way of influencing flavour in the cup.

Once separated from the rest of the fruit and washed, the beans need to be dried out to a water content of about 10% to achieve stability. To achieve this, they are laid out to dry in the sun on patios or drying tables until they contain around 12-13% moisture,
and typically then brought down to around 10% by machine. The whole process can be carried out in the machine but this generally only happens when there are space or humidity issues.

Once dried the coffee is in the parchment stage with a thin paper like outer skin on the bean which can be easily removed by ‘hulling’


The dry process is the oldest way of processing beans and is the most commonly used method in Asia and Ethiopia. It is sometimes also referred to as the natural process.

After harvest, the entire cherries are cleaned and sorted to remove unripe, over-ripe or damaged fruit, before being allowed to dry whole in the sun on patios or drying tables. It can take up to weeks for the cherries to dry. There is a significant risk of mould
developing, so the cherries have to be turned regularly. Rain is another potential issue as the whole crop could be ruined if subjected to a downpour.

Once dry, the complete cherry is hulled to remove the entire dried outer fruit covering all at once.


This is a mixture of the wet and dry processes. It is very popular in Brazil and is also being tried in many other countries as well.

The cherry is passed through a milling screen to remove the skin and some of the pulp like in the wet process, but fermentation or machine scrubbing does not follow. Instead, the resulting bean is then dried in the sun retaining many of the sugars of the cherry and creating a very interesting coffee.

Hulling and Grading

The parchment that is left coating the beans after they have been processed using any of the three methods is then removed or hulled mechanically by a process ranging from gentle whacking by a bespoke machine to the use of a very basic millstone.

The coffee is then sorted to remove defective beans, graded for size and quality, bagged and prepared for shipping in its green unroasted state.


Many thanks to Steve for this excellent insight into processing. You will find a host of valuable information on Steve’s brilliant ‘Hasbean’ app, including blogs, videos and brewing guides. You’ll also find him on Twitter @hasbean. He’s also one half of ‘Tamper Tantrum’ along with 3FE founder Colin Harmon – check out http://www.tampertantrum.com for all sorts of coffee geekery!

And that’s it for this edition, we look forward to catching up soon and continuing our journey through the world of coffee. As always you can find us on Twitter & Instagram @arch_coffee, or on Facebook at /archcoffee

Neil & George


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