Dark-roasted coffee is popular. So is light-roasted coffee. We design grinders that can handle both profiles – and everything in between. However, it’s important to know the differences between them. Even with the consistency of a Baratza grinder, you will need to make adjustments based on which profile you grind.
Dark and light coffees are pretty different from one another in terms of their physical and chemical properties. Your grinder will behave differently – and need to be used differently – depending on which roast you’re grinding!
There are three main ways that roast will affect the use and performance of a grinder: the grind settings you use, how you’ll need to clean and maintain it, and what kind of things can go wrong. Let’s consider some tips and tricks for each.
GRIND SETTINGS/OPERATION
Lighter coffee will typically need a finer grind for best results. Remember from our previous post that finer grinding increases surface area, which aids in extraction. Dark and light coffees have different solubilities and as such will extract differently.
Dark roasted coffee is less dense and has a lower moisture content due to the extended roasting process it’s been through. This means you’ll need a slightly coarser grind overall to achieve the same extraction.
Light roasted coffee is denser and has a slightly higher moisture content than dark roast, which will affect solubility in the other direction and make extraction a little more difficult. A finer grind compensates for that.
That added density also means that your grinder will take longer to process light roasted coffee. You can expect noticeable differences if you switch from one to the other, especially when grinding for espresso.
Roast intensity will also affect the way ground coffee behaves fresh out of the grinder. Dark roasts tend to be more prone to static, which can make grinding a little messier. Light roasts, on the other hand, tend to leave behind a thin, dry, papery material called chaff, which is a part of the coffee seed itself that is often burnt off in darker roasts. This chaff is incredibly light and also static prone. 
Our grinders are calibrated at the factory to accommodate as many users as possible, but with use over time you might find that your light roast is just not getting fine enough for espresso on your grinder. So, it’s helpful to consider changing the calibration of the machine. This is possible on all of our grinders, and you can find instructions on our troubleshooting page.
MAINTENANCE AND CLEANING
Every grinder needs periodic cleaning. Coffee leaves oil behind when you grind it, but dark roasted coffee tends to be particularly oily. If you grind dark roast in your machine, it’s a good idea to clean a little more frequently than if you grind light. That residual oil can gum up your burrs and slow grinding down, and it can slow down throughput as the discharge chute and paddle wheel get bogged down also.
More cleaning is always better, but a reasonable regimen to stick to is a thorough scrubbing of your burrs and grind chamber using the brush that came with your grinder every four to six weeks. Consider bi-weekly cleaning if you use particularly dark and oily roasts like French or Italian. 
Many users find it easier to purchase grinder cleaning tablets, which grind through the machine much like coffee. They’re often made of grain and will scrub out oil from the nooks and crannies of a grinder, leaving a clean surface (albeit covered in grain dust) behind. Just be sure to follow the directions that come with your brand of choice!
That residual oil will also stick to your hopper and grounds bin. We make these parts out of an antistatic plastic, but the static-eliminating properties are reduced by layers of oil from coffee. It’s a good idea to wash these parts in warm, soapy water – especially if you grind dark.
Speaking of static – darker coffee tends to be more brittle, which means extra fines and a higher propensity for static buildup during grinding. This can affect the distribution of particles in your dose and onto your grinder or counter.
The more brittle dark roast, however, is easier on your burrs. The difference isn’t huge, but light roast will wear your burrs a little bit faster. On average, a steel burrset in a Baratza grinder will last 500lbs of grinding before needing to be replaced. If you grind exclusively light roast, that number might be a few pounds smaller.
WHAT CAN GO WRONG
Like any machine, a Baratza grinder can experience malfunctions. Clogs and obstructions can happen regardless of roast, but there are a few differences in why and how.
Of course, it goes without saying that your coffee grinder should only be used to grind coffee. We don’t recommend grinding spices, nuts, or other non-coffee material as these will damage the machine.
Clogging is most often due to ground coffee backing up into the grind chamber. This will happen if a machine grinds too much coffee in a single operation. The lower density of dark roast means it can tend to pile up higher in a grounds bin, leading to a faster clog if you’re grinding in bulk. When grinding dark roast, the greater presence of oil will encourage clogging because that oil can build up and “gum up” the discharge chute, narrowing the passageway through which coffee moves.
While light roasted coffee isn’t as prone to these troubles, it doesn’t mean you can’t enjoy dark roast too – just be careful not to grind too much at once (the bin should not be more than 2/3 full), and stick to the cleaning regimen above.
It’s also important to remember that some roasts are simply too light for our grinders. Because very light roasted (or “white”) coffee is so dense, there’s a strong chance that components in your machine will get damaged during grinding. For this reason, we strongly discourage the grinding of unroasted, or only partially roasted coffee.
Foreign objects like stones or even screws can get into coffee at several points along the chain, from the coffee farm to your kitchen. Our machines have a built-in failsafe in case such an object passes through the grinder, so it will avoid serious damage. That being said, a repair – even a simple one – is another step between you and fresh ground coffee.
No particular roast profile can avoid a foreign object in a bag of coffee; it just happens from time to time and is part of the coffee experience. It’s worth noting, however, that darker roasted coffee is often selected from coffee farms with a greater focus on volume, which means sorting practices are not always as exhaustive there. This means a slightly higher chance of foreign objects in a bag of dark roast.
This is secondary to the roast profile, however. Because foreign objects in coffee can also cause flavor profile discrepancies, quality-focused roasting companies will sort out foreign objects as best as they can and companies who do not have the same focus will sort less, regardless of the roast degree. All of this is to say that selecting a quality-focused roast – dark or light – is the best way to avoid grinding a stone or screw.
At Baratza we like to say that the first, biggest step toward great coffee at home is the coffee itself. The second step is your grinder. A great roast – dark or light or somewhere in between – is crucial to enjoying your morning cup, and the grinder is your best tool for realizing the potential in that roast. Like any tool, it can be used differently in order to get the best results. In the end, your Baratza grinder gets the job done for any roast with just a little fine-tuning.