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How we roast your coffee part one

Updated: Nov 15, 2023


Hand roasted coffee is at the very heart of what we do. The hard work put in by the farmer, planting, cultivating the coffee crop, care and attention to detail lavished throughout the processing, grading and shipment could literally go up in smoke unless we get our bit right.

We might set out to create a well balanced blend with broad appeal or, we might want to create a single origin espresso bursting with fruity flavours. We will draw upon the expertise of coffee merchants such as Falcon Speciality Coffee, our previous experience and customer feedback. Samples will be sourced, roasted and tasted under laboratory style conditions before a decision on bean choice is made.

Green coffee, its origin, processing and the ethical side of coffee trading are hugely important areas to us. We will go into more detail about these areas in future articles, but for now, back to roasting.

Our coffee roaster is made by Giesen, a company situated in the Netherlands. They are a company with over 30 years experience in metal ware and have been exclusively making coffee roasters since 2006. Their machines are cast iron (ours weighs around 450 kilos) and lovingly crafted. Giesen machines are the roaster of choice for the World Coffee Championships and are becoming increasingly popular with UK speciality coffee roasters.

We have what is known as a drum roaster. The roasting chamber is a constantly rotating drum, underneath which is a gas burner. The roasting process works by applying 3 different types of heat to the coffee beans:

  • Conduction, is where the beans actually touch the bottom part of the drum, which is in direct contact with the flame.

  • Radiation from the hot surface of the drum, which passes right through the beans (think about standing next to a bonfire)

  • Convection from fans, where hot air is blown through the beans

On a top end roaster like our Giesen it is possible to manipulate each of these heat sources separately, giving total control over the roast.

Our roaster has a fully electronic control panel, but the actual roasting process is controlled by hand. The first thing to do after powering on the roaster is to pre-heat it. Pre-heating a coffee roaster helps achieve a good, even roast in line with previous observations. This is important, because having found a roast profile (settings) that work well with a particular coffee, we want to be able to repeat that consistently to ensure each batch of coffee tastes like what it is supposed to.

Whilst the roaster is pre-heating we prepare our green beans. Beans are weighed out into individually labelled buckets in small batches of between 4 -6 kg. Each batch is given a reference number which stays with the coffee from roast through to packing. This ensures that the traceability of the coffee continues through to the end consumer and helps us keep track of things internally.

green coffee beans before roasting

We also use this time to make sure we have everything we need at hand. These include roast profiles which contain information about the roast settings for the coffee in question and logs, so that we can record observations on the current days roasting.

We load the green coffee beans into the hopper situated at the top of the roaster. We then set the roaster to the correct start temperature for the particular coffee we are roasting. When the machine hits this temperature, we push a lever to drop the beans into the roasting chamber and press another button to start the roast timer.

In the next article, we will explain more about what happens to the coffee beans during the roasting process and how we manage the roasting process to its conclusion.

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