How And When to Clean Your Coffee Roaster


The coffee roaster is the central (and often most expensive) investment of any roasting business. So, it stands to reason that you’ll want to maintain it in optimal condition. Doing so not only increases its lifespan but also means that it produces clearer, better-tasting coffee – all while decreasing the risk of a breakdown or fire.

Don’t forget that your roaster is likely working day in and day out, with dust, smoke, and oils entering, being produced, and exiting the machine. You can’t overlook the importance of a good maintenance calendar to keep it running at its best.

I spoke with Doug Graf, long-time roaster technician of Vintage Coffee, and Bill Kennedy, President of US-based roaster manufacturer The San Franciscan Roaster Co, about their recommendations. Doug recently ran the Roaster Maintenance program at SCA Coffee Expo, while The San Franciscan Roaster Co presented The Coffee Roasting Institute.

Lee este artículo en español Cómo y Cuándo Limpiar tu Tostadora de Café

The SF-10. Credit: The San Franciscan Roaster Co

Creating a Maintenance Schedule

The first question you need to ask yourself is: how often?

There are a few factors that will affect the answer. If you’re using your roaster every day, you’ll need to perform routine maintenance more often than if you roast just a few times a week. Also, if you tend to produce darker roasts, the extra oils will mean more frequent cleaning is needed.

Don’t get complacent if you roast lighter, though. Bill cautions that “if you do lighter roasts, you’re going to be tempted to not clean often enough.” He points out that a loss of clarity due to reduced airflow will be even more noticeable in lighter profiles.

If you’re just starting out, you can observe how quickly buildup in your ducts and cooling tray develops in order to determine a cleaning frequency that works for you. This may involve a few weeks of frequently disassembling a section of ductwork to observe buildup development. Don’t wait for a noticeable change in your airflow before you break down your ductwork to inspect it.

Keep in mind that a little buildup in your pipes can lead to substantial losses in airflow. As Doug points out, the area of a circle (that is, the cross-section of an airflow duct) is calculated with r2. Therefore, a slight buildup on the edges of the pipe (a reduction of the radius, r) exponentially reduces the pipe’s area.

Upkeep should always be done before your machine is affected to such a degree that it impacts the profile of the roast, otherwise you’ll have to re-dial in your roast profiles every time you clean.

So, be proactive when developing a maintenance schedule and, then, crucially, stick to it. Doug recommends a schedule based on the number of days rather than the number of roasts. “People won’t reliably keep track of their number of roasts, and then [maintenance] may fall randomly on different days, at different times of the year, and it’s very difficult to treat it as a scheduled item,” he says. “If you’re doing it every Friday, for the sake of argument, then every Friday, it happens.”

Once you come up with an appropriate schedule, it’s important to keep a maintenance log, documenting all issues and corrective actions that you take with your roaster. This will help you stay consistent and diagnose issues when they arise.

And while every roaster’s specific maintenance schedule will be different, there are some general tasks that you can divide into daily, weekly, monthly, and yearly activities.

You might also like: Coffee Roasting Guide: What Is Airflow & How Can You Control It?

Loading coffee beans into a roaster

Loading coffee beans into an SF-6. Credit: The San Franciscan Roaster Co

Daily Tasks

Before any maintenance begins, there should be a safety protocol to “lock out” the electricity and gas supply to the roaster. You don’t want an accidental start or gas leak. Only once this has been done are you ready to start the cleaning and upkeep.

Most maintenance tasks revolve around ensuring a clean, consistent airflow. The first task is simply emptying the chaff bucket. This should be done every 8–10 roasts or before the chaff bucket is half full (or daily, depending on which is more frequent). “The efficiency goes down very drastically when the bucket is past half full,” says Doug, adding that “your likelihood of a fire goes up quite significantly.”

It's important to clean the chaff

A serious chaff backup. Credit: Doug Graf, Vintage Coffee

Another task that should be performed daily is checking the cooling tray and ensuring that no holes are clogged up. A stiff-bristled roller is an effective tool for this.

Outside of these two tasks, simply wiping down the roaster and keeping the area around it clean is a first-line defense against the dust buildup that inevitably happens.

Lastly, Doug emphasizes that “it also just comes down to simply paying attention.” On a daily basis, you should inspect electrical connections and the water and gas lines for any potential issues. You’ll want to also be observant of any sounds, vibrations, or anything else out of the ordinary.

Weekly Tasks

On a weekly basis, you should use a vacuum cleaner to clean out underneath the cooling tray and around the burners. Compressed air should be used to blow out the motors to the fans and any other motors, and then any dust should be vacuumed up.

The interior of a neglected cooling tray. Credit: Doug Graf, Vintage Coffee

This is also a good time to top up the lubrication on any lubricated joints or moving parts with a high-temperature, food-safe grease. “You want to be careful not to over-grease,” cautions Doug, but do pay attention to your bearings to make sure they’re not wearing.

You should also clean your thermocouple, which will probably only require some gentle scrubbing with a scotch pad or steel wool to remove any buildup. Bill says, “I always make a mark on the temperature probe to make sure that you’re not getting a different reading because the depth is [different].”

Monthly Tasks

This is when the deep cleaning begins. You should disassemble and thoroughly scrub the ductwork for the roaster and the cooling tray. Remember, preventing buildup in these sections is critical to clean-tasting coffee and preventing fires from becoming unmanageable.

Fires usually begin in the roaster or chaff cyclone. However, Bill tells me, “If a fire starts and there is all that material build-up inside the pipes, and if that catches fire while the blower is operating, it can become as hot as a blacksmith forge inside… It’s also the reason that the venting is so expensive and has the very high heat ratings in case such an event happens.”

Disassembled ductwork ready for a long-overdue scrubbing. Credit: Doug Graf, Vintage Coffee

Remove and thoroughly clean the fan to your cooling tray and the roaster’s exhaust fan, too. When finished, the Kaowool (or Kaowool paper) and aluminum tape used to connect the duct joints should be replaced, and all gaskets should be replaced as well.

The month-mark is also a good time to clean out all green coffee contact areas, primarily the hopper. If your hopper has a glass porthole on the side, you’ll be able to see the dust and oil buildup every day while roasting. If it doesn’t, don’t get tricked into complacency – buildup is still happening.

A dirty fan that is long overdue being cleaned. Credit: Doug Graf, Vintage Coffee

You should also deep clean your chaff collection bin and your cooling tray, scrubbing out any dust and oils from the interior walls. You can also revisit the fluid levels in the motors, as well as inspect and, if necessary, re-grease the drum bearings on the front of the roaster.

Yearly Tasks

About once a year, an even more thorough maintenance day is called for. “Most machines have a yearly breakdown,” says Doug, “and it’s just a more in-depth version of [the monthly tasks].”

The tasks at this point are more specialized, such as checking the amperage draw on motors or measuring airflow and pressure through pipes, inspecting afterburners on the roof, and so on.

Some roasters may feel comfortable taking care of these tasks themselves. Others may not have the technical know-how or the time for such a thorough inspection. In that case, it may make sense to call in outside help.

“It’s really company-specific,” says Doug, but adds that bringing in an additional perspective can help any roaster. “Getting a fresh pair of eyes and a fresh set of ears on something… can be very useful.”

On this note, being able to get in touch with your roaster’s manufacturer or a third-party expert can be important, especially if your roaster is down. Bill says that, at The San Franciscan Roaster Co, they aim for an immediate response time when roasters have an issue. Ask your manufacturer how long you can expect to wait should something go wrong. And, when you create your maintenance log, add the contact information of a responsive technician. After all, if your machine’s not running, you’re not roasting stock and your customers’ orders are going unfulfilled.  

A cracked ceramic plate on a coffee roaster’s burners. Credit: Doug Graf, Vintage Coffee

Roaster maintenance is a dirty job. Equipping yourself with the right tools and gear can be the difference between a tough but efficient day of scraping and dangerous and laborious exercise.

Because you’ll be peering into disassembled pipes and cramped spaces, a headlamp is extremely useful. Also, eye protection is important to protect yourself from flying shards of loosened creosote and buildup. A sturdy pair of gloves will protect your hands, and a dust mask isn’t a bad idea either when you’re scraping, blowing, and vacuuming.

An extremely dirty pipe with significantly reduced airflow. Credit: Doug Graf, Vintage Coffee

Besides vacuums and a compressed air gun, the principal tool for removing buildup from pipes is a simple scraping tool. Doug tells me, “I take most of my scrapers and round them over so they match the inner diameter of the pipe. It makes a huge difference.” An angle grinder and a needle gun can also be effective in some situations, but the manual scraper is still the go-to tool.

Scraping pipes takes a fair bit of physical work. For this reason, Bill prefers to use a heavier gauge steel in his roasters: “The buildup from the coffee is going to be pretty, let’s say, robust,” he tells me. “If you have a good heavy-gauge steel construction, it will take all kinds of scraping and chipping and whatever sort of thing that you need to do to get it out.

“Steel is steel, but if you have a very thin-gauge steel… over time, those things will start to fatigue.”

There are a few solvents and degreasers that you can use to reduce how hard you have to work. Bill mentions Simple Green, Super Blast Off, and Easy-Off oven cleaner. Doug, for his part, swears by TSP – Trisodium Phosphate mixed with hot water.

With solvents like these, you can soak sections of piping for a few hours and greatly reduce your scraping load. However, be careful not to use solvent on food-contact surfaces, determine how many chemical products in general you want to be using, and if you have a large roaster, ask yourself how practical it is to soak sections of ductwork.

The SF-75, which can roast up to 300 lbs per hour. Credit: The San Franciscan Roaster Co

“It’s impossible to get good coffee without good maintenance,” Doug says. Bill agrees, telling me, “It should be part of a regular, high-functioning business model.”

Long-time roasters tend to hold the opinion that, sooner or later, a roaster fire is inevitable and a clean roaster isn’t immune to a fire. However, dirty airways stress fan motors, increasing the potential of a burnout and fire.

And, as Bill points out, “if you have a fire in a hot, dirty roaster, the fire is going to be more catastrophic.” Ultimately, the buildup that develops in air ducts is extremely flammable.

Maintaining your roaster can be hard, tedious work and it can be tempting to put it off, and then put it off, and then put it off again. But if your goal is superior quality, consistency, and protecting your investment, then thorough, regular maintenance is a no-brainer.

The roaster “is a machine that needs to be in tip-top tune,” says Bill. “You’re honoring the farmer by doing that, and you’re honoring the client who’s buying your coffee.”

Enjoyed this? Read: Coffee Roasting Guide: What Is Airflow & How Can You Control It?

Feature photo credit: The San Franciscan Roaster Co

Please note: This article has been sponsored by The San Franciscan Roaster Co.  

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Source: Perfect Daily Grind

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