A Simple Guide to Chemex Paper Filters

The Chemex is a beautiful glass coffee pot, but it's just a simple container. The real magic comes from the special paper filter that goes inside it.

The filter was designed by a chemist. Its thickness and the way it's made are what create the famous clean taste of Chemex coffee.

This guide will walk you through everything about the Chemex paper filter. We'll cover the different types, how to use them, and why they work so well.

Types of Chemex Filters

To understand Chemex filters, you need to know three things about them. This includes their material, their shape, and their product code.

White vs. Brown Filters

The biggest choice you'll make is between white and brown filters. This isn't just about looks. It changes the flavor of your coffee and how you brew it.

• White Filters: People call them "bleached," but Chemex doesn't use harsh bleach. They use an oxygen-cleansing process with hot water baths. This removes any papery taste from the filter.
• Brown "Natural" Filters: These filters are brown because they skip the oxygen-cleansing step. They only get hot water baths.
• How They Taste: The brown filters can make your coffee taste woody or like cardboard. To avoid this, you have to rinse them with a lot of hot water before brewing. The white filters taste much more neutral, so most people prefer them for better-tasting coffee.

Both types of filters can be put in your compost bin.

Filter Shapes: Square, Circle, and Half-Moon

The different filter shapes can be confusing, but the choice is pretty simple.

• For large brewers (6-cup and up), Chemex says that square and circle filters work the same way. The choice is just about what you prefer.
• Square Filters (FS-100): These are the classic ones with two points that stick up. Many people like them because the points make it easy to lift the hot, wet filter out of the brewer.
• Circle Filters (FC-100, FP-1): Some people like these because they sit flush with the top of the coffee pot for a cleaner look. The FP-1 filters come unfolded so you can fold them yourself.
• Half-Moon Filters (FP-2): This shape isn't a style choice. It's a smaller filter that you must use for the small 3-cup Chemex brewers. They are sold unfolded because of their smaller size.

Although Chemex says the square and circle filters work the same, some people find that the square ones drain much slower.

What the Product Codes Mean

The product codes are an easy way to know what you're buying.

• FP-2 / FP-2N: These are the small Half-Moon filters for the 3-cup brewer. FP-2 is the white version, and FP-2N is the brown (Natural) version.
• FS-100 / FSU-100: The "S" is for Square. These are the large filters. FS-100 is the white version, and FSU-100 is the unbleached version.
• FC-100: The "C" is for Circle. This is the large, pre-folded white circle filter.
• FP-1: This is the large, unfolded white circle filter.

Which Chemex Filter Size Do I Need?

A lot of people get confused by Chemex sizing. Here's the most important thing to know: there are only two sizes of Chemex filters.

The system is split into two groups of brewers. And a Chemex "cup" is about 5 ounces, not the standard 8.

The Two Filter Sizes: Small and Large

• Small Brewers (3-Cup Models)
  • This group includes the small Chemex brewers like the Classic (CM-1C) and the single-cup Funnex (CM-FNX).
  • These brewers only work with the small, unfolded Half-Moon filters: FP-2 (white) and FP-2N (natural).
• Large Brewers (6-Cup and up)
  • This group includes all other Chemex models: the 6-cup, 8-cup, 10-cup, and 13-cup brewers.
  • All of these brewers use the exact same large-size filter . The cone angle is the same on all of them, only the pot below is bigger.
  • This one-size-fits-all filter comes in four styles: square (FS-100), unbleached square (FSU-100), circle (FC-100), and unfolded circle (FP-1).

This is why you can't find a "10-cup filter." You're just buying the same FS-100 filter that also fits the 6-cup and 8-cup models.

Quick Chart: Brewer and Filter Matching

This table gives you a quick guide for buying the right filter.

Can I Use Regular #2 or #4 Filters?

People often ask if standard #2 or #4 cone filters work in a Chemex. The answer is no . Those numbers are for a totally different sizing system used in automatic drip coffee machines.

• Why They Fail in a Chemex:
  1. Shape: Regular filters often have a flat bottom seam. This shape doesn't fit the Chemex's true cone shape.
  2. Strength: These filters are thin. They aren't strong enough to hold the weight of wet coffee grounds in a Chemex and can rip or collapse.
  3. Purpose: Using a thin, generic filter misses the whole point of a Chemex. The thick, special paper is what makes the coffee so good.

Where to Buy Chemex Filters

Finding Chemex filters can sometimes be tough because they're popular and can sell out. It's best to check both big stores and local shops.

Big Stores and Online Shops

These stores are convenient, but they are often the first to run out of stock.

• Amazon: Sells all types but they are often sold out.
• Crate & Barrel: A good place to check for both brewers and filters, but stock can be unreliable.
• Williams Sonoma: Carries several types of filters.
• World Market: Often has good prices but can also be out of stock.
• Target: You can buy Chemex filters on Target's website, but it's very rare to find them in the actual stores.

Buying directly from the Chemex website can be expensive because of high shipping costs. This pushes more people to buy from other stores, which makes them sell out faster.

Your Best Bet: Local Coffee Shops

If you're searching for "Chemex filters near me," your best option isn't a big department store. You'll have better luck at a specialty coffee shop.

• The "Secret" Stash : High-end coffee shops and local roasters often use Chemex to serve their coffee.
• Why it Works: Since they need the filters for their own business, they usually stock them for customers to buy too. They are often the last place to run out when big stores are empty.
• What to Do: The best thing to do, especially during a shortage, is to call your local coffee shops. This is the most reliable way to find filters right away and supports a local business.

How to Use a Chemex Filter

The Chemex filter is very thick, and the glass brewer is smooth. Because of this, you have to use a specific technique to avoid problems.

The whole process is designed to prevent two main issues: clogging the filter and creating an airlock. Following these steps is important for a good brew.

What Filter to Use with Chemex?

Here's a quick reminder on sizing.

• For 3-cup brewers, use the FP-2 or FP-2N half-moon filters.
• For 6-cup and larger brewers, use any of the large filters (like the FS-100 or FC-100 ).

Folding the Unfolded Filters

• For Half-Moon (FP-2):
  1. Fold the half-moon in half to make a quarter circle.
  2. Find the small tab at the corner and fold it in.
  3. Fold it in half again to make a wedge.
  4. Open the cone so there are three layers of paper on one side and one layer on the other.
• For Unfolded Circle (FP-1):
  1. Fold the circle in half.
  2. Fold it in half again to make a quarter-circle.
  3. Open the cone with three layers on one side and one on the other.

The Most Important Step: Placing the Filter

This is the key to a successful brew.

• The Rule: Place the filter in the brewer with the 3-layered side facing the pouring spout.
• Why it Matters: The smooth glass of the Chemex can create a vacuum seal when the thick paper gets wet. This "airlock" stops the coffee from draining. The spout is the only place for air to escape, and the thick, 3-layer side of the paper keeps the filter from collapsing and sealing it off.

Should You Rinse a Chemex Filter?

Yes, you should always rinse the filter with hot water. This is a required step for a few reasons.

1. Flavor: Rinsing washes away any papery taste. This is very important for the brown filters but is also a good idea for the white ones.
2. Heat: The big glass pot can cool down your brew water, leading to weak coffee. Rinsing with hot water preheats the brewer.
3. Sticking: The rinse helps the filter stick to the glass walls. This keeps it from shifting when you add your coffee grounds.

After you rinse the filter well, pour out the rinse water through the spout. Be careful not to move the filter.

What Grind Size is Best for Chemex?

The right grind size is medium-coarse .

• Why it Matters: The Chemex filter is 20-30% thicker than regular filters, which slows down the water flow.
• What Happens: If your coffee grounds are too fine, the small particles will clog the paper's pores. This can stall the brew, making it take too long and causing your coffee to taste bitter.
• The Right Grind: The grind should be coarser than what you'd use for a normal drip coffee maker, but finer than for a French Press.

How to Stop Your Chemex From Clogging

If your brew stalls, it's usually because of an airlock or a clogged filter.

• Symptom: The water in the filter is draining very slowly or not at all.
  • Problem 1: Airlock
    • Cause: The filter has sealed against the glass and blocked the spout. This can happen if you put the 1-layer side against the spout by mistake.
    • Solution: Gently lift the edge of the paper to let air escape. You can also place a chopstick in the spout before brewing to keep an air channel open.
  • Problem 2: Clogging
    • Cause: The coffee grind is too fine, or your grinder made too many fine particles. These tiny bits have choked the filter.
    • Solution: There's not much you can do for this brew. Next time, just set your grinder to a coarser setting.

Chemex Filter Alternatives

Since the filters can be expensive and hard to find, many people look for other options. It's important to know the difference between reusable filters and emergency substitutes.

Reusable Filters: Metal vs. Cloth

Using a reusable filter isn't really a substitute. It's a choice to change your brewing method completely .

• Paper (The Standard): The Chemex paper filter removes all oils and fine grounds. This makes a very clean, crisp, and bright cup of coffee.
• Metal (like the Able Kone): A metal filter is the opposite of paper. It lets all the oils and many fine grounds pass through.
  • Taste: This gives you a richer, full-bodied, and heavier cup of coffee.
  • The Tradeoff: This full body can hide the more delicate fruity and floral flavors of the coffee.
• Cloth (like the CoffeeSock): Cloth filters are somewhere in the middle.
  • Taste: They trap the grounds like paper but let some of the oils through, creating a balanced cup.
  • The Tradeoff: They are hard to clean. You have to rinse them well, boil them sometimes, and store them wet in the fridge to keep them from getting gross.

Can I Use a V60 Filter in a Chemex?

It's not a good idea, as it usually doesn't work well.

1. Fit: V60 filters have a slightly different cone angle and can fall into the pot.
2. Thickness: The V60 filter is much thinner. This makes the coffee brew much faster and taste different, more like a V60 coffee than a Chemex.
3. Airlock: The thin paper is also more likely to collapse and seal the spout, causing an airlock.

Can I Use Regular #2 or #4 Filters in a Chemex?

No. As we talked about earlier, this will not work. The paper is too thin and will rip, and the shape doesn't fit.

What Can I Use If I Run Out of Chemex Filters?

These are last-resort methods and are not recommended because they can be unsafe and make bad coffee.

• Paper Towel: This is a common trick, but paper towels aren't made for food. They can contain chemicals, glues, or bleach that can get into your coffee. They also tear easily and can leave fibers in your drink.
• Clean Cloth Napkin: A safer option is a clean, tightly woven cotton or linen towel. This works like a DIY cloth filter and is a much better choice than a paper towel.

Why Are Chemex Filters Special?

So why go through all this trouble for a specific paper filter? The reason is simple: it makes a unique cup of coffee and might even be healthier for you.

The "Bonded" Paper

The filter is a piece of lab equipment. The chemist who invented it based it on laboratory-grade paper.

• The Thickness: The key feature is that Chemex filters are 20-30% thicker and heavier than other coffee filters.
• The Function: This thick paper is made to remove things you don't want in your coffee. It traps bad fats, oils, bitterness, and all the fine coffee grounds.

The Result: A Super "Clean Cup"

By filtering out all the oils and grounds, the Chemex filter makes a coffee with a very special taste.

• Taste Words: People describe the coffee as "exceptionally clean," "crisp," and "very mild."
• Flavor: By removing the sludge, this method lets the coffee's delicate fruity and floral flavors really stand out. Many people find it tastes sweeter, with no bitterness at all.

A Healthier Brew? The Link to Cholesterol

This is the biggest science-backed benefit of using a Chemex filter.

• The Science: Coffee beans have natural oils that contain compounds called diterpenes.
• The Health Risk: One of these compounds, cafestol, is known to raise your cholesterol levels, especially the "bad" LDL cholesterol.
• Problem Brewing Methods: Unfiltered coffee, like from a French Press or Turkish coffee, is very high in these compounds.
• The Paper Filter Solution: Paper filters are very good at trapping these compounds.
• The Chemex Advantage: Because Chemex filters are the thickest paper filters available, they are extremely good at removing the cafestol.

The "richness" that people like in French Press coffee comes from the oils that the Chemex filter is designed to remove. So, the "clean cup" from a Chemex is not just a taste preference. It can also be a healthier choice .

Are Chemex Filters Really Necessary?

Yes. The filter is the most important part of the brewer. Using a different filter won't make a Chemex hybrid brew; it will just make a bad cup of coffee.

• V60: Uses a thin filter and a cone with ribs. This is designed for a fast flow, letting more oils and fine particles through.
• Chemex: Uses a thick filter and a smooth cone. This is designed for a slow, controlled filtration where the paper does all the work.

They are two different ways of making coffee. You can't get that classic clean, oil-free Chemex taste without the Chemex filter.

Common Problems and Questions

The biggest frustration for Chemex owners, besides learning the brewing method, is that the filters can be hard to find.

Why Are Chemex Filters So Hard to Find?

The filter shortages aren't a new problem. They happen because of how the company is set up.

1. High Demand: The popularity of specialty coffee and more people working from home has made demand for Chemex filters go way up.
2. Manufacturing Limits: This is the main issue. Chemex is a small company that makes its filters in-house in the USA. The process is very manual, and they are already making as many as they possibly can.
3. Supply Chain: The whole operation depends on a specific type of wood pulp and their own factory. If anything disrupts that, like a factory shutdown or a shortage of wood pulp, their entire filter production stops.

The company's small-scale process is what makes the filters great. But it also means they can't easily make more when demand is high.

What People Are Saying

Here's a final summary of what experts and regular users think about the Chemex filter.

White vs. Brown Filters: The Verdict

The feedback here is very clear. The white, oxygen-cleansed filters are much better .

The brown filters, even with a lot of rinsing, give the coffee a papery or woody taste. This unwanted flavor hides the nice flavors of the coffee beans. If you care about taste, the white filters are the way to go.

A Note on Filter Quality

This is an important point for anyone buying Chemex filters today. There are many reports from people online saying that Chemex filters have been getting thinner over the years.

• The Complaint: People who have used Chemex for a long time say that new filters feel much thinner and smoother. They don't have the same thick, rough texture they used to.
• Why This Breaks the System: This is a huge problem because the entire Chemex brewing method relies on the filter's thickness.
  1. It Causes Airlock: The thinner paper is more likely to collapse into the pour spout.
  2. It Causes Clogging: When the paper collapses, it creates the exact airlock problem the 3-layer technique is supposed to prevent.
  3. It Causes Slow Brews: This leads to the coffee stalling and brewing for way too long. The result is bitter, over-extracted coffee.

While Chemex has denied any changes, the complaints from users are very common.

This is a big deal. If the filters are actually thinner, it ruins the whole point of the Chemex system. The thick filter is the one thing that makes it special.

The original Chemex filter is an amazing product. But just be aware that many people have reported this drop in quality and the brewing problems that come with it.