When you brew coffee and hot water pours through the grounds, the filter allows the rich flavor into your coffee pot or mug, while keeping the grounds separate. It’s a morning ritual we barely think about, but I got to thinking about the wide variety of coffee filter types, and whether this plays an important role in determining the quality of coffee.
Does it affect the flavor? What are coffee filters made of, and does the material impact the taste? What about the different shapes and sizes?
Let’s break down some interesting details about this simple yet vital component of a good brew.
How coffee filters work
The purpose of a coffee filter is fairly straightforward: after the hot water has dissolved the flavor compounds of the coffee beans, and absorbed their taste, color, and aroma, the filter separates this liquid from the grounds. This filter is often (but not always) made of disposable paper—thin and porous enough to allow liquid through, but not the tiny grains of coffee. Essentially, a filter traps the grounds and other particles that you don’t want to drink. The filter you choose influences what gets into the coffee and what stays out.
What coffee filters are made of
Just as the type of coffee bean influences flavor, so does the filter material. The most common coffee filter types are paper, metal, and cloth.
Paper coffee filters
Paper coffee filters are one of the most commonly available filters. You can easily find them in any grocery store. They are used in drip coffee makers and are both highly absorbent and tightly woven, removing the majority of excess oils and grounds for a cleaner liquid. Without these particles, coffee may seem more acidic, but this is a matter of perception.
Paper coffee filters are typically available in a cone shape or a basket shape (above), and in different sizes for compatibility with your coffee maker. Melitta coffee filters, among other brands, are available in white, natural brown, and bamboo.
How to use a paper coffee filter
There are several ways to use a paper coffee filter, depending on the brewing method. Using a paper coffee filter with a coffee maker is the most universal method. These appliances are relatively affordable and found easily in many stores. After setting up the coffee maker, you fill up the water tank and insert the paper filter into the pull-out compartment. Then, measure out the desired amount of coffee and pour the grounds into the filter. Replace the compartment and turn on the coffee maker to brew.
Other methods use paper coffee filters as well, such as pour-over. This method requires a cone filter and a cone. You start by bringing the water to a boil separately. Place the paper filter inside the cone and saturate it with hot water. Place the cone on a pot or mug, measure the coffee grounds into the filter, and pour in the water, allowing water to extract compounds from the coffee grounds as it passes through and emerges into the pot or mug.
What kind of paper are coffee filters made of?
Coffee filters are typically made with paper that weights 100 grams per square meter. Melitta also offers bamboo-based paper filters. The type of paper impacts the brewing process, as the coffee filter pore size plays a role in what makes it through.
Bamboo coffee filters by Melitta.
Why are some paper coffee filters brown and some white?
The filter’s color depends on whether the paper is bleached (white) or unbleached (brown). While neither of these options will affect the quality of the coffee, unbleached filters are more environmentally friendly. Bleached coffee filters take paper away from its natural color, which is brown.
Metal coffee filters
Metal coffee filters provide a different experience from paper filters. The mesh inevitably has larger pores, so it doesn’t block as much of the natural oils or small grounds of coffee. Even the best metal coffee filter will allow some particles and residue through, but that’s not necessarily a bad thing. The coffee filter pore size is still tiny, which makes the particles barely noticeable.
Many people find that this extra body, and the accompanying oils that get through, actually give you a much richer taste and fuller mouthfeel than you get with a paper filter. Certain flavors only present themselves when the oils are present, offering a sweetness that paper filters remove.
How to clean a metal coffee filter
Metal coffee filters can be tricky to clean. When cleaning coffee filters, you should consider both daily upkeep and monthly deep cleaning. On a daily basis, old coffee grounds need to be tossed into the garbage or compost pile, and the filter needs to be washed with soap and water. If there are any grounds that get stuck in the filter holes, they should be wiped out or plucked out.
These daily washings are enough to prevent too much buildup, but a monthly deep cleaning session is needed to keep coffee fresh. You can do this a few ways:
- Soak the filter in soap, water, citric acid, and hydrogen peroxide for four hours.
- Boil the filter in white vinegar and water mixture (1:13) and allow it to soak overnight.
- Clean the filter with a coffee filter cleaner (like Urnex Espresso Machine Cleaning Powder).
After this wash, make sure to thoroughly rinse and wash with soap and water as a final step.
Cloth coffee filters
The least common coffee filter material is cloth, although these filters have a lot of benefits. Like paper filters, cloth filters do a great job of capturing all the coffee grounds. However, as with a metal filter, you still get all the oils that contribute to the coffee’s flavor. By brewing coffee with this material, you get a rich cup that contains no unsavory grains or particles.
While cloth can provide a good middle ground between paper and metal filters, upkeep is a chore. Between each brew, these filters need to be washed, but you shouldn’t let them become too dry or too moist. Usually, cloth filters last for about 30 brews before the micro-grounds and oil start to permeate the taste of the coffee. However, they can be used for about 100 brews safely.
Coffee filter shapes
Just as the material plays a role, so can the shape of the coffee filter. Coffee filters are available in cone, basket, and disk shapes for different brewing styles.
Cone coffee filters
Cone filters are the best coffee filters for pour-over brewing methods. They come in different sizes, depending on the type of coffee maker used. While a size No. 1 fits the one-cup coffee makers, the size No. 6 filters are meant for 10-cup coffee makers. There are No. 2 and No. 4 sizes in between. Consult the instructions for your coffee maker to find out which one you need.
Basket coffee filters
Basket coffee filters are commonly made to fit nearly every model of basket coffee mater. The shape is much like a large cupcake wrapper, and it is likely the image that most people think of when coffee filters are mentioned. While their opening towards the top is wide, the bottom of this filter is flat and wide.
Cone vs. basket filter
You might be wondering if the taste of your coffee would change if you switched from a cone to a flat bottom coffee filter.
The answer, according to coffee scientists at the UC Davis Coffee Center, is yes!
They recently conducted a study on this very question. They partnered with Breville, a company that makes coffee makers and whose Precision Brewer can brew with either a cone or a basket filter. They tried it with both, and kept all other variables such as roast level, water temperature and flow rate exactly the same.
Participants in their study tasted the coffees and were able to tell the difference. They described different flavor notes depending on the shape of the filter.
The researchers are still trying to learn why this happens. They know that a change in filter shape changes how the water flows through the grounds and therefore how the coffee molecules are transferred into the water. They are investigating the details of that process.
Disk coffee filters
The disk filter is mostly used in AeroPress brewers, though they sometimes are used to replace filters for Fresh press machines. They are significantly smaller than the others on this list, and their sizing varies according to the coffee maker with which they are intended to be used.
Coffee filter sizes
It is important to choose a filter that serves the number of cups that you want to brew.
Cone filters are sized by numbers, depending on the amount of coffee each one is meant for. Most automatic coffee makers can brew four to six cups (No. 2), eight to 12 cups (No. 4), and 10 cups (No. 6) at a time. (Note that these are small, five-or-six ounce cups rather than the 12-ounce “Tall” cup you would get at Starbucks.) Two-cup non-electric makers can use the No. 2 cone filter. Anyone who wants to brew a single cup of coffee will need a size No. 1.
Basket coffee filters have a standard size, although anyone who wants to brew fewer than six cups of coffee will need to seek out junior-size basket filters.
Brand-specific coffee filters
Filters for Chemex have up to 30 per cent more weight than other brands, allowing them to remove the finest of particles like cloth filters can. However, these filters also remove oils and fats, using a cone shape to filter water through the grounds. They produce a very clear cup of coffee.
AeroPress coffee makers generally use the brand’s paper filters, although a metal replacement is available and preferred by some. AeroPress paper filters are fully compostable and they are not designed for any other brewer.
Hario V60 filters
Hario V60 uses a standard cone shape with a single large hole at the bottom of the dripper. Their branded filters are made of natural pulp, and no chemicals are used to create them. While a trapezoid filter could be used in a pinch, the company states that “delicious coffee” can only be made with their filter.
Coffee filter substitutes
Waking up to grind your coffee only to find that there are no filters can throw off an entire morning. Fortunately, there are a variety of household items that can act as a coffee filter substitute.
Paper towel coffee filter
Perhaps the most accessible and direct alternative is to grab a paper towel or napkin and fold it into your coffee maker to cover the space the filter would have.
Toilet paper coffee filter
Toilet paper can work this way as well and may shape to fit more easily into the coffee maker. However, be careful dumping the coffee grounds as this filter substitute can fall apart and make a mess.
For a reusable coffee filter substitute, try using a scrap of cloth in your coffee maker. Muslin or fine grain cheesecloth provide a dense enough material to trap the grounds while allowing full flavor coffee to seep through, but other tightly woven cloth will do.
Sock coffee filter
In a real pinch, people have been known to use a (clean!) sock. Environmentally friendly and portable, you can skip the coffee maker and simply put the grounds inside the sock, holding the sock over a pot or mug, and pour hot water directly through the sock.
Cloth options can all be washed and reused, so you’ll always have a backup on hand.
Coffee filter FAQ
Do coffee filters affect taste?
Coffee filters do affect the taste of coffee, but not in a way that will be obvious to everyone. The quality and shape of the filter both play a role in flavor. Anyone who is particular about taste should prioritize the quality of filter over a low price.
Do coffee filters go bad?
Filters generally don’t come with an expiry date. If you’ve had filters sitting for a long time and want to use them up, there are several ways to ensure they don’t go to waste. Try using them as disposable snack bowls for pretzels, popcorn, etc. Filters carry no lint so they make excellent screen cleaners for phones and computers. And you can use them to remove sediment when you pour the last of the wine.
Can you reuse coffee filters?
Most coffee filters can be used several times before they stop giving you the quality of coffee you want. Just rinse them immediately after use and leave them to dry. If you want to replace your coffee filter less often, buy a metal filter that can be used for years.
Can you compost a coffee filter?
Yes. Both the coffee filter and its used coffee grounds can be put in the compost pile. Decomposition happens relatively fast, especially if the filter is buried rather than kept near the top where it can dry out.
Will paper towel work as a coffee filter?
You can use a paper towel as a coffee filter in a pinch. Measure two tablespoons of coffee into the paper towel and slowly pour hot (but not boiling) water over the grounds, allowing the liquid to strain into a cup.
Will coffee filters filter water?
Yes. If the water is particularly dirty, the filter will eventually become clogged and water will have a hard time passing through. That’s when it’s time to change to a new filter. Even after filtering, water should be boiled before consuming to kill pathogens such as bacteria and viruses.