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One of the most important steps to keeping your coffee maker in tip-top shape is descaling. It’s different than cleaning because cleaning removes coffee stains and oil buildup, while descaling removes minerals, or scale, that attach to and crystalize on your brewer. Initial scale buildup can look like a chalky, powdery substance, and over time, scale buildup can get so gnarly that it looks like rock candy and, worse, it can clog your machine!
Luckily, descaling an at-home machine is really easy. The biggest challenge is just remembering to do it. Pro tip: I actually have a Google calendar reminder set every month. The next hardest challenge is choosing the right descaler. I’ve tested a few options and then my fellow Kitchn writer Ever Meister, a specialty-coffee professional, recommended I try using Milliard Citric Acid. So I decided to give it a spin!
Unfortunately, this product took weeks to get to me. As I waited to get my package, I looked around the internet and found that many coffee cleaners and descalers were either out of stock or on backorder, which makes sense: People are still brewing coffee at home and demand for products to keep their machines in top shape is likely higher than it’s ever been.
Scale is caused by the buildup of calcium carbonate, which is found in most tap water. If you live in a place with hard water, that means there’s a lot of dissolved minerals — one of them being calcium — and scale will accumulate faster. That’s why I always recommend using some sort of filtration system when brewing coffee, like a Brita filter. You don’t want to use totally distilled water, though, because you need some of those minerals to bind with the coffee grounds and pull flavor out.
Citric acid is a naturally occurring substance found primarily in — you guessed it — citrus fruits. As a versatile product, it’s a powerful detergent often found in cleaning products. And it’s also a chelating agent, which means it can help bond to and remove metals. The citric acid I bought is food-grade, and if you look on the label of many beverages (especially soda), you’ll find citric acid listed as one of the ingredients. Some people refer to it as a “sour salt” because it looks just like salt in powdered form.
Almost every descaling solution on the market consists of, or is made primarily of, citric acid. Some products might have other chemicals to either stabilize the formula or aid in removing stains and oils, but citric acid is still the primary active ingredient in most descaling solutions. “There are other compounds that are specifically there to dissolve mineral deposits other than calcium that can get in coffee boilers,” says Jackson O’Brien, a trainer and technician for Peace Coffee in Minneapolis. “Where I’m at in the world, calcium is really all I see so that’s why citric acid is all I use.” Plus, citric acid is (usually, unless there’s a shortage) readily available, easy to use, and inexpensive. The bag of Milliard that I bought is strictly citric acid. Nothing else.
When my packets of Milliard finally came, I was excited to test it out on my Technivorm Moccamaster. There wasn’t too much scale on the machine — thank you, Google reminders — but I did observe some white powder in the brewing tank and the metal spout where hot water pours over the coffee grounds.
How I Tested the Citric Acid as a Descaler
The Milliard packets didn’t come with instructions, so I had to look up the ratio of water-to-product to use. Most websites suggest using two tablespoons of citric acid to one liter of hot water and to dissolve the powder into the water. I then poured the water-citric acid mixture into the brewing tank and started a brewing cycle — you want the citric acid solution to touch every surface that interacts with water, so the most effective way to descale your machine is to run a descaling solution through the brewer.
Immediately, I noticed that the water collecting in the carafe was a light blue color. “An acidic solution reacting directly with copper will leech ions from the copper, which is a bluish-green, depending on intensity,” says O’Brien. “Same reason that Lady Liberty is green, despite being made of copper … it means your boiler was mostly clean to start with and the acid is dissolving the metal. It won’t hurt [the brewer] unless you perform a descale every day.”
Once the brew cycle was over, I ran a cycle with just water to clear out all of the solution. Afterwards, I checked the water reservoir, and I noticed that a lot of white powder was gone. I wiped the reservoir down with a microfiber cloth to give it a final polish. I also pulled off the water spout, and except for a few old coffee stains, most of the white scale was gone. For the most part, the citric acid cleaned the majority of scale off, and I was happy with the results. You can see for yourself!
My Honest Review of Using Citric Acid to Descale a Coffee Machine
Overall, if you have hard water, citric acid is a great option to descale your machine. As of this writing, a five-pound bag of citric acid costs about 34 cents per ounce, which is cheaper than most fancy descaling solutions. That said, I don’t necessarily think citric acid does any better than any other descaling solution, and if you already have a product you love, feel free to stick with it!
Just don’t use vinegar: vinegar, or acetic acid, will descale your machine (almost any acid will) but it will make your coffee taste like vinegar for weeks. Because there are porous surfaces in your brewer, the vinegar can leach into those surfaces and linger for a long time.
Truly, the best advice I can give is just to descale regularly! One friend suggested descaling every time the pack of coffee filters runs out — that’s a great visual indicator (that’s about every 50 brews, which my friend estimates is about once every two months).
I descale every month because this is my area of expertise and a monthly task is much more feasible for me than doing it when the coffee filters run out (I will 100% just ignore that or say something like, “I’ll do it tomorrow.”). Descaling is the single-best thing you can do to preserve the longevity of your brewer and keep it running well for years to come.
How do you descale your coffee machine? Tell us your tips in the comments below.