With so many coffee filter options, you might be confused hearing terms like micron or particle size and wonder what it even has to do with coffee. Don’t worry; we’ll clear it up for you. The word micron is short for micrometer, and it is a tiny unit of measurement.
One micron is one-millionth of a meter or 0.001 millimeters. Most people cannot see things smaller than 40 to 50 microns, such as bacteria. For comparison, one strand of hair averages around 70 microns.
When it comes to coffee, the term microns (represented as μm or um) refers to the pore size of a filter; larger pores mean a larger micron number. A 20-micron filter, for example, will catch particles 20μm in size and larger.
The Importance Of Coffee Filter Size
Not only are coffee filters different shapes and sizes to accommodate several kinds of brewers, but the micron rating is vital if you’re particular about how your coffee tastes.
Filtered coffee is popular because it produces a clean taste. Health-conscious coffee drinkers also love this method because it catches oils that may harm your health.
Coffee filters, in particular paper and cloth ones, can catch diterpenes, compounds that may raise cholesterol levels. If you’re in fairly good health and don’t drink excessive amounts of coffee, this doesn’t mean unfiltered coffee is bad for you, but it’s good to know if you want to keep an eye on your cholesterol.
The micron size of the coffee filters will influence how many diterpenes are caught and the flavor of your coffee. The smaller the filter, the crisper and purer the coffee will taste. Larger micron filters will allow more oils and small coffee grounds through, attributing to a more robust drink.
The micron rating of coffee filters can range from 10μm up to a few hundred, but the average seems to be between 10μm and 20μm, especially for paper filters. The most influential factor in determining the micron size is the material of the filter; for example, a metal filter will typically have a larger micron size than a paper one. This is because the fibers in paper and cloth are more tightly woven together.
Coffee Grind Sizes
Below are the recommended grind sizes for the most common brewing methods, even if they don’t require coffee filters. Although you’re free to experiment, sticking to these figures will help you deliver the classic flavor profiles associated with each of these coffee beverages.
- Turkish coffee: 100μm
- Espresso: 200-400μm
- AeroPress: 300-500μm
- V60: 500μm
- Moka pot: 500μm
- Chemex: 700μm
- French press: 1000μm
- Percolator: 1000μm
- Cold brew: 1000-1500μm
Types Of Coffee Filters and Their Micron Size
Paper coffee filters are the most common. Since they’re single-use, they’re the most convenient.
The micron size for paper filters is the smallest, typically ranging from 10μm to 20μm. Paper coffee filters leave coffee with a light, refreshing feel as they catch most of the oils and sediments.
Aside from standard paper filters, you can find filters made from bamboo. It’s unclear if the micron size differs from standard paper filters and bamboo, but they are growing in popularity as bamboo grows quicker than trees, making it easier to replenish. Learn more in our bamboo vs. paper filter guide.
Metal coffee filters are usually made from stainless steel. Gold tone filters are simply stainless steel filters with gold plating.
These filters are reusable, which makes them popular among eco-conscious coffee drinkers. Metal filters usually have larger pores, typically coming in at 50μm to 200μm. For example, metal filters for an AeroPress are 178μm.
Using metal filters results in coffee with a richer mouthfeel as they do not catch oils. The downside is that the more absorbent paper filters can also prevent some unsavory flavors from developing in coffee, but metal filters can’t. To avoid this, always use high-quality coffee.
Cloth filters are also reusable. They’re a good in-between as they tend to catch more sediments than metal filters but still allow some oils through that contribute to a more robust coffee taste.
Although there is little data on the exact micron size of cloth filters, they are usually made from a blend of cotton and hemp. The micron size of cotton fabric is generally between 11μm to 22μm, while hemp ranges from 16μm to 50μm, so cloth filters should fall between these ranges.
Components of filters, such as the dripper cone from a V60 or the rim of metal filters, may be plastic, but it’s uncommon to find fully plastic coffee filters. This is because plastic can impart odd tastes in your brew, which increases with time as this material can absorb flavors and aromas.
They’re also rare due to potential health concerns. Bisphenol-A (BPA) is often added to make plastic more resilient, but excess exposure has been linked with infertility, cancer, metabolic disorders, and more.
Heating BPA, including from the coffee brewing process, can cause more of this chemical to leach out. According to the FDA, up to five milligrams of exposure to BPA per kilogram of body weight is safe per day.
These days, BPA is less common due to its bad reputation, but some BPA-free plastics may also be harmful. Since plastic is so prevalent in our daily lives, a coffee filter is unlikely to be the biggest culprit of BPA exposure.
If you do find a fully plastic filter, they’re usually a multi-purpose basket that you can also use to steep tea or strain water when cooking. Nylon mesh filters can range from 11μm to 160μm, but some may be even larger.
Some paper filters will contain small amounts of polypropylene (PP) plastic to help them retain their shape, but it’s unclear if this will alter the micron rating.
Choosing The Right Coffee Filter
Depending on your brewing method, you might be limited in coffee filter choices.
Brewers like AeroPress and Delter require small circular filters. Paper is the most common choice, but you can find reusable metal versions.
Despite looking similar, these filters can’t be used interchangeably as there are slight variations in the size and texture of AeroPress and Delter filters. Learn more in our AeroPress vs. Delter guide.
Chemex and V60 are both pour-over methods brewed using cone-shaped filters. However, the filters used in a Chemex brewer are thicker. The bigger filter is why Chemex coffee tastes cleaner than V60, as it can absorb more oils.
Conical filters brew stronger coffee because the brewing process is slower. The coffee is also more evenly extracted as all the grounds gather in the center, making it easier to saturate them fully.
Flat Bottom Filters
Cone and flat bottom filters can be used in electric drip coffee brewers. Both of these kinds of filters come in different sizes depending on how many servings of coffee you want to brew.
Flat-bottomed filters don’t fit well in Chemex and V60 brewers. Although you could use these filters, since the coffee makers are conical themselves, they could easily shift and spill the grounds during the brewing process.
Flat bottom filters also may not extract evenly if the water doesn’t saturate the coffee grounds equally.
Hario Siphon Filters
Siphon brewers notably use thick cloth filters. However, you can use paper or metal ones. The unique filter likely contributes to siphon coffee’s full-bodied yet crisp drinking experience.
Bleached Vs. Unbleached Filters
Whether your paper coffee filter is bleached or unbleached doesn’t impact the micron size, but it is something many coffee connoisseurs consider. Most coffee lovers don’t notice a difference in taste between these kinds of filters.
Bleached filters have been treated with oxygen or chlorine. Some health-conscious coffee drinkers prefer to steer clear of them; research from the ‘80s noted that dioxins in bleached filters could harm health. With that said, they are generally regarded as safe, as very little chlorine is used these days.
The larger concern for many coffee drinkers is the environmental impact. Filters treated with chlorine are less eco-friendly as the manufacturing process can create toxic by-products.
As mentioned earlier, filters with a smaller micron number will make for lighter, cleaner-tasting coffee as they catch more natural oils and grounds. Larger micron filters can achieve that if you like coffee with a rich, full body and deeper flavors.
Impact Of Coffee Ground Size On Filter Choice
Depending on the size of your grinds, you might be limited to certain filters. Using a large micron filter with very fine coffee grounds is a recipe for disaster; if the ground coffee is finer than the filter, it will spill through.
Using fine grounds with a large micron filter also results in under-extracted coffee as it escapes before the flavors are fully developed.
Conversely, extremely small grinds can clog fine micron filters as the coffee clumps together while you add the water. To avoid this, grind a little coarser.
Coffee Roasts And Brewing Methods
Coffee roasts also play a role in grind size and brewing methods, but you can use your knowledge about coffee filters to make some unique beverages.
One of the reasons dark roast is used to brew quick cups of coffee, like espresso, is because it’s more soluble; this allows for the flavors and caffeine to be extracted quicker than light roasts. As finer grounds are required for these methods, they also brew quicker due to the increased surface area. The combination of the quick brewing method and fine grounds prevents astringent and burnt flavors from developing in the brew.
However, by using the micron size of filters to your advantage, you can use filtered coffee brewing methods to make dark roast shine. Since larger micron filters brew a little quicker than finer ones, you can use these to get a rich dark roast flavor profile while reducing the bitterness developing in the coffee.
Another example of playing around with roasts, grind size, and filters is using quick brewing methods for light roasts. Light roasts are typically best brewed with slow methods, like drip coffee, as they need more time to extract the flavors. However, if you’d like to use a quicker method, such as an Aeropress, with a light roast, you can use finer grinds for easier extraction with a metal filter to ensure the full floral flavors can still come through.
The Final Word
There are so many kinds of coffee filters to cater to the tastes of all coffee drinkers. There are different filters for each brewing method, and the material helps determine the taste of the final brew.
Consider your grind size when choosing a filter to ensure your coffee can brew correctly; the grounds must be larger than the microns in your filter. After that, you can experiment with filter materials, shapes, and pore sizes to create your perfect cup of coffee.
Who Invented The Coffee Filter?
The coffee filter was invented by Melitta Bentz in the early 1900s. She was seeking a way to make a cleaner cup of coffee as, in those days, people waited for the grounds to sink to the bottom of the cup. She poked holes in her son’s blotting paper, and the rest is history.
What Is The Best Coffee Grinder?
A burr coffee grinder is your best option for more control over your grind size. These grinders are more consistent than blade grinders and can be calibrated to meet the grind size requirements for all brewing styles. The ability to create even grounds means smaller particles won’t escape through your filter.
Why Are Coffee Filters Bleached?
Paper coffee filters are usually bleached to give them a cleaner appearance, which makes them look more desirable to customers. Some coffee drinkers also feel these filters have a less paper-like taste.
Why Do We Grind Coffee Beans?
Although you could make coffee with whole beans, it’s a slow, wasteful process. Coffee beans are ground to increase the surface area. This allows for more flavors to be extracted from a single coffee bean.