Getting consistent, high-quality results from each batch on your coffee roaster is important – it shows your customers that you’re reliable, professional, and committed to selling great-tasting coffee.

However, as with any other piece of precise industrial equipment, consistency can degrade over time with regular use. So, what can roasters do to keep their machines consistent? And how should they be maintained? 

To answer these questions and learn more, I spoke to two coffee roasters and a specialist service technician. Read on to find out what they told me.

You might also like our article on using the right ventilation system for your roaster.

Why is consistency important?

For roasters, there is understandably a focus on developing a roast profile for each new coffee they bring in. A “perfect” profile will unlock the flavours hidden within the green beans, allowing the coffee’s best qualities to shine through, whatever they may be.

Once this perfect profile is developed, however, the roaster faces their next challenge: replicating it consistently from batch to batch. 

Luis Fernando Velez is the owner of Amor Perfecto, an award-winning roastery based in Bogota, Colombia. He tells me that it’s incredibly important that roasting technology returns on the investment by producing consistent results for customers. 

“A few weeks ago, a Korean company ordered a huge amount of coffee from us,” Luis says. “They needed 16,000kg of coffee, and we roasted it in five days. We had no issue with the machines [and their consistency].”

Ultimately, having a reliable and consistent roaster allows businesses to respond to these kinds of large orders. It allows them to move quickly, removing any bottlenecks from the process of roasting coffee itself.

Luis also explains that a roaster has an obligation to deliver consistency not just for the customer, but also for the farmers they source from. Roasting coffee to a consistently high degree of quality upholds the producer’s reputation just as it does the roaster’s. 

“[This is why we] put the name of the coffee grower on the bag,” Luis says. “I find it interesting, as in the past, many roasters wouldn’t do that. They were afraid their competitors would go and buy the coffee too.

“However, my philosophy is that if [another roaster] goes to the farmer and buys the coffee, I’ve done my job correctly.”

So, what can go wrong with your roaster?

Over time, regular use of a roaster will naturally cause parts of it to wear down and fail. Machines can also get “clogged”, generally thanks to various buildups that occur during the roast (chaff and coffee oils, for instance). 

Any kind of damage or failure due to continuous use can, over time, affect batch consistency – so keeping your roaster clean and well-maintained is certainly in your best interest.

Joe Thill is a roaster technician at Usonian Systems. He says: “Roasters have what we call ‘wear parts’; expendable components that are generally meant to be fairly interchangeable and can be relatively easily replaced.

“These wear parts prevent wear on other parts of the roaster, which are either more expensive or more difficult to replace – often both.”

However, by understanding which parts of your roaster are designed as “wear parts”, you can target your maintenance, prolong their life, and protect your machine in the long term. This, consequently, will help you to be more consistent. 

“One area where I see lots of buildup is the cooling fan assembly,” Joe says. “All of the ducting attached to the cooling fan is especially prone to a buildup of coffee oil. This condenses on the inside of the duct tubes, and forms a sludge. Over time, this can lead to decreased efficiency in the cooling fan.”

The cooling fan is an essential part of a roaster, as it helps to precisely control and manage temperature during the roast. As the cooling fan becomes less efficient and precise, accurately recreating roast profiles will become more and more difficult.

Joe also notes that how you roast and the profiles you use can actually affect how quickly these buildups occur. With darker roasts, more oil migrates to the surface of the bean as the sugars develop, meaning more escapes into the roaster itself. 

“Roasters that are regularly producing darker roasts for multiple hours a day are definitely going to see an increased buildup of that coffee sludge,” Joe says. “To address it, you can just blow out fan motor housing with a can of compressed air or something. That’s how we clean those fan blades.”

Batch size matters

Another detail to keep in mind for machine maintenance is the batch size of your roaster. As a roasting business grows, it will naturally require larger machines to meet increasing demand. 

A higher batch size can also help increase consistency, however. Roasting two 10kg batches instead of one 20kg allows more room for deviation. 

In a wholesale setting, however, Joe explains that larger roasters are more likely to be used for darker espresso roasts rather than filter roasts (purely because of demand). Consequently, in his experience, this means larger roasters tend to suffer more from these buildups.

“Even though high-capacity roasters have a larger tubing size for their venting to accommodate, we generally see that darker roasts are more frequent and more prevalent in larger roasters,” Joe says. “They also tend to run more often and have higher workloads, [causing more of a buildup].”

Ultimately, while investing in larger capacity roasters helps to make your roasts more consistent, it also makes regular maintenance even more important.

How can roasters keep their equipment consistent?

Some parts of a roaster will naturally wear down over time with regular use. David Fullerton is the owner of Acoustic Java, a roastery based in Worcester, Massachusetts. He tells me that he uses a Loring S35 Kestrel, but notes that there are specific components he keeps an eye on in particular.

“So far, it’s just the non-steel parts,” he says. “Components such as the edges of the cooling bin paddle fins and the hose connecting the rolling loader bin cart to the roaster hopper.”

He says that a regular maintenance schedule can help you maintain these components – the “wear parts”, as Joe calls them.

David says: “There are some daily maintenance tasks [you can take on], such as emptying the chaff barrel. After that, of course, there are weekly, monthly, and annual tasks, from cleaning the cyclone spray nozzle to checking the exhaust stacks and cleaning as needed.” 

However, roasters should be wary that depending on the age of their roaster, a different approach to keeping things consistent should be taken. For instance, modern Loring roasters rely on airflow to roast the beans, as opposed to classic gas drum roasters. This means they require a different approach to maintenance.

Joe says that ensuring consistency with a Loring starts with making sure airflow control is as precise as it can be. “The key is blowing out the fan motor housing with compressed air (or something similar). A lot of the time, that can dramatically increase efficiency in all of your fans. 

“In a Loring roaster, you have a couple of different motors controlling a couple of different fans throughout the roaster. Making sure those parts run at peak efficiency is important for longevity… it’s the most important part of the roaster, and the most expensive component to replace.”

Other steps

However, a regular in-house maintenance routine alone may not help you maximise roster consistency. There will naturally be times throughout your roaster’s life cycle where something extra is needed.

For instance, Joe tells me that Usonian offers yearly and bi-yearly service programmes to ensure their customers’ machines are always functioning at the optimum level. They offer a technical service package with an on-site visit from a skilled, experienced technician.

Joe says: “This includes identifying a few different parameters and taking measurements, things along those lines. We have a basic standardised checklist of things to go through, such as paddle measurements within the drum.”

Taking these measurements allows the service professional to monitor any wear or degradation over time, comparing it to figures from previous years to understand how the machine is changing.

However, it’s not just a mechanical or technical service that you should focus on. David also notes that software upgrades can help your machine stay consistent from batch to batch, too.

“Usonian recently upgraded our machine with ‘turbo burner’ software. They facilitated the entire process with us, in collaboration with Loring.

“Thanks to careful planning, we experienced no downtime, and our few follow-up operational questions were addressed by the technician as they arose following the successful installation.” 

Finally, having a specialist on-hand for any more immediate issues can help maintain consistency if your roaster suddenly encounters dramatic difficulties. For instance, Luis tells me that remote support from Usonian helped with a major order. 

“​​Before [started on a contract that required us to roast] 1,000kg over five days, [our larger roaster stopped working at 100% power]. We called Usonian, and received [everything we needed remotely] to recalibrate the burner. That was it.

“All it took was a couple of hours on the morning before we started roasting, and we were ready.”

Batch consistency should be a key priority for any specialty coffee roaster, but maintaining it over time is easier said than done. However, the more you understand about the inner workings of your machine, the better equipped you will be to understand why consistency changes, and what you can do to help.

Ultimately, creating daily, weekly, and monthly maintenance schedules will be key. However, in the long term, partnering with a technical specialist and making sure your machine is regularly serviced is invaluable. 

Enjoyed this? Then you’ll like this article on upgrading your coffee roasting space.

Photo credits: Usonian Systems

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