Recently, world-renowned coffee consultant and published author Scott Rao, published an insightful blog post,  discussing the ins and outs of buying a new coffee roaster. Throughout his career, Scott was fortunate enough to roast on hundreds of coffee roasting machines and he is now making it his mission to help new roasters to buy the right machine for their needs.

Follow the link for the original blog entry HOW TO CHOOSE A ROASTING MACHINE


Genio is proud to say that we comply with all of the features that he lists as essential for any roaster purchase including design, craftsmanship, smart technology, technical support and of course our friendly service. 

So if you are in the market to purchase a coffee roaster, sit a little closer as Scott shed some light on this daunting topic.


What should I include in my budget when planning to purchase a new coffee roaster?

Firstly, consider how much you can afford to spend on a roaster. When calculating your budget, don’t forget to include the cost of necessities such as chimney ductwork, pollution-control equipment, initial green-coffee inventory, QC equipment, a laptop for logging roast data, and various supplies. A budget should also include the costs of installation, permits, and architectural drawings for the permit process.

Do you have any guidelines on roaster sizes?

If you can afford it, please buy a larger roaster than you think you need. I’ve never known a roaster to regret buying a machine that was a bit too large, but I’ve known many roasters who regretted buying machines they quickly outgrew. Once you’ve estimated the startup costs of your roasting operation, prioritize your wants and needs.

To choose the proper machine size, it’s important to estimate how much coffee you expect to roast each week over the next two years. Note the weekly amount of coffee you expect to roast two years from today. I recommend buying a machine large enough to roast that quantity of coffee in no more than 25 hours. When performing these calculations, remember that a machine’s real capacity is likely less than its stated capacity and that beans lose 14%–20% of their weight during roasting. (For reference, third-wave roasts lose approximately 14%, while a Starbucks roast may lose 20% or more.) A machine’s burner capacity—not its drum size—determines how much coffee it can roast well.

A reasonable guide is to assume that a quality roast of one kg of green coffee requires 11,500 kj/hr (or, one lb of coffee requires 5,000 btu/hr).*

*This formula does not apply to machines that recirculate hot air back into the roasting chamber. Recirculation machines have higher capacity relative to burner output.

Your roasting-machine salesperson will likely claim that you can roast 15 kg per batch in a 15kg machine. The job of a salesperson is to sell machines, not to help you roast the best-possible coffee, so take any claims lightly. The salesperson may be technically correct because the drum can surely fit a 15-kg batch, but a full batch may take 15:00–20:00 to roast, which is longer than ideal. If quality roasting is your goal, it’s usually safe to assume you will roast 3–3.5 kg batches per hour at 50%–70% of a machine’s stated capacity. Then deduct the 14%–20% weight lost per batch to calculate how much roasted coffee per hour a machine can produce.

How do you rate the reliability of a coffee roaster?

Some machines are more reliable than others. Roasters with fewer parts, fewer high-tech features, and heavier builds tend to be more durable and reliable. Of course, all design decisions entail trade-offs. Some modern technology may lack reliability but make quality roasting easier and more repeatable. Again, ask other users about reliability before buying— I’m sure most roasters would be happy to share their experiences, especially if they have complaints! While roasters are not always objective about their own roast quality, they tend to be somewhat objective about the reliability of their machines.

How important is after-sales service for coffee roasters?

After-sales service and technical support are very important! Many brands may not offer service or support in your country. Further, some companies offer poor support once you have paid for your roaster. Even if you have a pleasant initial sales experience with a company, that does not guarantee future after-sales service quality.

Would you consider the roaster’s control system as an important consideration with this purchase?

This may seem like a trivial consideration, but if you’re going to spend 20–40 hours per week using a roaster, a well-designed user interface is important. The interface isn’t just about convenience and comfort, it can also affect roast quality and repeatability. For example, machines that require you to repeatedly tap an up- or down-button to change the gas setting can be tedious and slow to respond. In comparison, a machine with an analogue gas dial or a smart touchscreen is more responsive, makes it easier to replicate curves, and can be a pleasure to operate. Other ease-of-use considerations involve having large, well-positioned digital manometers, timers, and temperature readouts.

What is the best way to include my new coffee roaster into the decor of my shop?

You may want to consider aesthetics if you are installing a roaster for use in a retail cafe or other public space. A beautifully refurbished vintage machine may make a nicer impression than a budget, modern machine.

Also, remember these practical tips for the area the coffee roaster will be installed:

  • Floor scale: Choose a sturdy floor scale with a resolution of no more than 0.005 kg (0.01 lbs) and a maximum capacity greater than the weight of your largest batch plus the bucket in which you will weigh that batch. You may want a scale with an even larger capacity if you plan on blending together full batches. The scale’s resolution must be precise enough to provide useful weight-loss calculations. 

  • Spotlight: I recommend mounting a lamp with a full-spectrum bulb just above the bean trier. While I recommend using the trier sparingly, it should be well-lit for those rare times you use it.

  • Fire-suppressionI recommend hard-plumbing a water line into the roasting-machine faceplate and chaff collector. The water line should include a spray head with an easy-to-access valve. This is probably the best insurance you can have against a roaster fire.

Are there any small accessories that I will need to purchase extra?

Over the years have I compiled this list of small accessories for setting up a new coffee roastery, but please consider this list only as a starting point (it is not comprehensive):

  • Large scoop for green coffee

  • Large scoop for roasted coffee

  • Buckets for green coffee

  • Separate, larger buckets for roasted coffee

  • Bucket labels and markers

  • Tables or counters for weighing, bagging, and boxing

  • Empty bags and boxes

  • Heat sealer

  • Wet/dry vacuum for cleaning chaff collector

  • Brush for chimney cleaning

  • Rags for wiping oil from buckets and cooling bin

  • Knife and/or scissors for cutting open green-coffee bags

  • Commercial dishwasher (if you can afford it)

  • Cupping supplies

  • Packing tape

  • Label printer

  • High-temperature, food-grade silicone (for resealing pipes after cleaning)

  • Grease for bearings

  • Flashlight

What are the pros and cons of the different roaster designs? 

Classic drum roasters: In these machines, a drum rotates above a gas flame, and a fan pulls hot air from the burner through the drum and out of the roaster. Most smaller machines are classic drum roasters. Classic drum roasters get the job done, though many models provide too much conductive heat transfer, due to having a thin single-walled drum or an improper distance between the burner and drum. If too much heat is transferred to the beans via direct contact with the drum, coffee will taste harsher and less delicate. If you choose a classic drum roaster, I suggest you seek a machine with a double-walled drum and a burner with sufficient btu/hr (or kj/hr) for your needs. Compared to other designs, classic drum roasters offer good thermal stability but slower responses to gas changes.

Indirectly heated drum roasters: In these machines, the burner chamber is separated from the drum and hot air passes from the burner chamber through the drum. The design allows the drum’s surface to remain cooler because the flame is not in contact with the drum. Indirectly heated roasters are more difficult to control than classic drum roasters, because they require skillful management of airflow, while classic drum roasters rarely require much if any, airflow adjustment.

Recirculation roasters: These machines recirculate a portion of the roasting exhaust air back through the burner and roasting chamber. Such machines are energy-efficient but often run the risk of imparting smokey or polluted flavours on coffee. To avoid smoke taint, it’s important to heat the recirculated air to a sufficiently high (afterburner-level) temperature before passing it through the drum.

Fluid-bed roasters: These machines rely on a bed of rising hot air to circulate the beans and keep the beans aloft. Fluid-bed roasters eliminate the risk of conductive-heat damage and are usually capable of developing beans well in short amounts of time. While there is no theoretical downside to fluid-bed roasters, in practice their control systems are usually too simplistic to fullfil the machines’ potential. Given the current, rapid evolution in roast-control and data-logging software, I expect the utility and popularity of fluid-bed roasters to grow rapidly in the near future.

What features of my coffee roaster will contribute directly to the quality of the roast?

Even though the following features are not necessary to roast a good batch of coffee, they will defiantly improve the quality and repeatability of the roast:

Double drum (applies only to classic drum roasters) and powerful burner: The foundation of a good classic drum roaster is its burner and drum. As noted previously, burner output determines a machine’s true capacity. Double drums allow for faster and hotter roasting with less risk of tipping or scorching. Make drum quality and burner output your first two concerns when choosing a classic drum roaster. You can easily replace or upgrade fans, valves, ducts, etc, but you cannot easily replace a drum, and upgrading a burner can be expensive.

Variable-speed-drive (VSD) fan: As long as your roaster’s fan provides a reasonable amount of draw, you don’t need a variable-speed fan to produce good roasts. But without a VSD fan, it’s impossible to maintain consistent airflow levels day to day. The combination of a digital air-pressure manometer and a VSD fan is essential for expert-level roast repeatability.

Air manometer (aka drum-pressure manometer): A manometer in the duct between the roasting drum and exhaust fan is a relatively new, worthwhile addition to a roaster. The manometer reads pressure, not flow, but that pressure reading correlates with airflow. Using the same fan setting every day does not ensure consistent roasting because airflow may vary day to day with the weather and other factors. Having an air-pressure manometer helps one know how to adjust the fan to provide consistent airflow every batch. (Note: directly measuring airflow requires installing probes in the exhaust duct, but the probes get dirty too quickly during roasting to work effectively. Using an air-pressure manometer is the best current option to monitor and maintain consistent airflow batch to batch. However, the relationship between pressure and flow will shift slowly as the ducts get dirty, so frequent chimney cleaning is critical.)

High-resolution gas manometer: Most roasting machines come with small, cheap analogue manometers that offer imprecise gas-pressure measurements. I recommend replacing your stock analogue manometer with a high-resolution digital manometer. Analogue manometers may be aesthetically pleasing, but they make discernment of precise readings too difficult.

Proper probes and probe locations: To be a great roaster by today’s standards, one needs better green, lighter roasts, quality data collection, precise controls, and software to track and analyze the data. To ensure adequate data collection, insist on having a bean probe and an environmental probe, each with diameters of 2.5 mm– 4 mm. An inlet-temperature probe is helpful but not critical.

The optimal bean probe location in most machines is as follows:

  • The probe’s tip should be 3–5 cm from the inside of the machine’s faceplate.

  • The probe’s tip should be 3–5 cm from the inner drum edge.  (2 cm is acceptable for machines with a capacity of 1 kg or less.)

  • The probe tip should be in the heart of the bean pile, even when roasting very small batches. If the probe is too high in the drum or too close to the centre axle, it may not be immersed in the bean pile of very small batches. Proper probe location should provide quality data for batches as small as 20% capacity.

How can I avoid paying rent on an empty roastery and loses money while waiting for my machine to arrive?

Manufacturers typically require the buyer to deposit 50% of the machine’s price upon ordering, with the balance due upon shipment of the machine. The problem with such arrangements is that a manufacturer routinely promises a machine in three months, secures a deposit, and then only ships the machine six to nine months later, claiming unavoidable delays. I strongly suggest insisting on a sales-contract clause guaranteeing delivery by a certain date, with a penalty against the manufacturer for late delivery.

In summary, what should I look out for when choosing a new coffee roaster?

  • Ensure a brand’s machines are reliable
  • Seek out features that assist in precision roasting
  • Find a company that offers prompt, reliable service, with service representatives based in your country
  • Cost (relative to burner output and features)

When choosing a roaster, I suggest you determine your budget, make a prioritized list of your needs and wants, and ask other roasters about their experiences with various machines. Trust others’ opinions about machine reliability and service, but be sceptical of their opinions about roast quality unless they have had extensive experience on numerous models of roasters. When possible, arrange with the manufacturer or another roasting company to spend a few hours working on a model of machine before committing to its purchase. 



For more information about this topic and other industry insight, Genio can strongly suggest Scott’s latest book, The Coffee Roasters Companion.  As fellow coffee professionals, we find this book an excellent tool to introduce both new and seasoned veteran roasters to the concept of Rate-of-Rise and the flavour profiles of your roasts.  The Coffee Roasters Companion book is available on his website and on our own Genio Online Shop – launching soon!