Chemex Brewing Guide: Ratio, Technique, and Step-by-Step Instructions

The Chemex is the most elegant coffee brewer ever designed. Its iconic hourglass shape, invented by chemist Peter Schlumbohm in 1941, has been in the permanent collection of the Museum of Modern Art since 1943. More importantly, it brews exceptional coffee.

The Chemex's defining feature is its proprietary filters — 20-30% thicker than standard paper filters. These heavy filters trap oils, fine particles, and waxes that pass through other filters, producing a cup that's remarkably clear, bright, and clean. If you want to taste the origin character of a specialty coffee without distraction, the Chemex delivers it.

This guide covers everything you need: equipment, the right Chemex ratio, grind size, step-by-step instructions, and how to troubleshoot common problems.

What you need

Essential equipment:

• Chemex (6-cup is the most versatile; 3-cup for one person, 8-cup for brewing large batches)
• Chemex filters (square or pre-folded; proprietary — standard filters won't work)
• Gooseneck kettle (pour control matters more with Chemex than any other method)
• Burr grinder (hand grinder for $40-60 or electric for $100+)
• Scale with timer (essential for repeatability)
• Fresh coffee (whole bean, roasted within 2-4 weeks)

Why a gooseneck kettle matters: The Chemex's large cone requires a slow, controlled pour to keep the coffee bed saturated evenly without overflowing. A regular kettle's wide spout pours too fast and creates uneven extraction. A gooseneck kettle ($30-50) is the most important Chemex upgrade.

Total beginner investment: $120-180 (Chemex $40-55, gooseneck kettle $30-50, hand grinder $40-60, scale $15-25).

The Chemex ratio

The Chemex's thick filters mean slightly less extraction efficiency compared to other pour over methods. This calls for a standard to slightly stronger ratio.

Recommended Chemex ratio: 1:15 to 1:17

Start at 1:16. It's the SCA (Specialty Coffee Association) standard and the most balanced starting point. Use the Brew Calculator to calculate exact doses for your Chemex size.

Adjusting for taste:

• Stronger, more body: 1:15 — more coffee relative to water
• Lighter, more delicate: 1:17 — less coffee, more transparency

Chemex grind size

Chemex requires medium-coarse grind — between French press (coarse) and standard pour over (medium). The thick filters slow drainage, so a slightly coarser grind prevents over-extraction.

Target grind: 700-900 microns, or grind index 48-56 on the BrewMark universal scale.

Translate to your grinder with the Grind Converter:

• Comandante C40: ~24-28 clicks
• Baratza Encore: ~22-26
• Fellow Ode Gen 2: ~5-6
• 1Zpresso JX: ~28-33 clicks
• Hario Mini Mill: ~24-28 clicks

Visual reference: Chemex grind should look like coarse sand — chunkier than table salt, finer than sea salt. If you see fine powder mixed in, your grinder may produce inconsistent particle sizes.

Step-by-step brewing instructions

Step 1: Heat water

Bring water to a boil. While it heats, weigh your coffee (30g for the recipe below).

Target water temperature: 200-205°F (93-96°C). If you don't have a thermometer, let the water sit 45 seconds off boil. Light roasts benefit from the hotter end; dark roasts from the cooler end.

Step 2: Prepare the filter

Open the Chemex filter and place the thicker side (three layers) toward the spout side of the Chemex. This creates an opening for air to escape during brewing.

Rinse the filter with a full cup of hot water to:

1. Remove paper taste
2. Preheat the Chemex
3. Seal the filter against the glass

Discard the rinse water. The Chemex will feel warm to the touch — that's correct.

Step 3: Add coffee grounds

Measure and grind 30g of coffee to medium-coarse (grind index 48-56). Pour the grounds into the center of the filter. Give the Chemex a gentle shake to level the bed.

Place the Chemex on your scale and tare to zero.

Step 4: Bloom pour (0:00 to 0:45)

Start your timer. Pour 60g of water (2× the coffee weight) slowly over the center of the grounds, spiraling outward to wet all the coffee evenly. Don't pour against the filter walls.

Let the coffee bloom — you'll see it puff up and release CO₂ as a dark crust. This is called degassing, and it indicates freshly roasted coffee. Wait until 0:45.

Why bloom? Freshly roasted coffee releases CO₂ that can prevent even extraction. The bloom lets CO₂ escape before you add the remaining water. If there's no bloom (no puffing), your beans are stale.

Step 5: First main pour (0:45 to 1:30)

Starting at 0:45, pour 150g of water in slow, steady spirals from the center outward. Keep the pour low and controlled. Aim to add 150g over 45 seconds — that's a slow, deliberate pace.

Maintain the water level about 1 inch below the top of the filter. Don't pour so fast that the filter overflows.

Step 6: Second main pour (1:30 to 2:30)

At 1:30, pour another 150g of water using the same spiral technique. Slow and steady. Your total water so far: 60 + 150 + 150 = 360g.

Step 7: Final pour (2:30 to 3:00)

At 2:30, pour the remaining 140g of water to reach your target of 500g total. Keep the spiral pattern consistent.

Step 8: Wait for drawdown (3:00 to 4:30)

Stop adding water. Let the coffee drain through the filter naturally. Total drawdown should complete by 4:00-4:30.

If drawdown takes longer than 5:00, your grind is too fine — coarsen up 2-3 clicks next time. If drawdown completes in under 3:30, your grind is too coarse — fine down 2-3 clicks next time.

Step 9: Remove filter and serve

Once the last drop falls, remove the filter and spent grounds in one piece. The Chemex carafe is now ready to serve.

Chemex coffee continues to stay hot in the glass carafe (glass retains heat well) and doesn't continue extracting. You can pour all cups at once or serve over the next 15-20 minutes without significant flavor loss.

Troubleshooting

"My coffee tastes sour or weak"

Cause: Under-extraction — not enough flavor compounds dissolved.

Fixes:

• Grind finer (2-3 clicks)
• Use hotter water (205°F instead of 200°F)
• Pour more slowly during bloom pour
• Use a stronger ratio (1:15 instead of 1:16)

"My coffee tastes bitter or harsh"

Cause: Over-extraction — too many compounds pulled from the grounds.

Fixes:

• Grind coarser (2-3 clicks)
• Use cooler water (198-200°F)
• Use a lighter ratio (1:17 instead of 1:16)
• Shorten total brew time (aim for 4:00 instead of 4:30)

"Drawdown is taking forever (5+ minutes)"

Cause: Grind is too fine — dense bed slows drainage through the thick Chemex filter.

Fix: Go coarser by 3-4 clicks. Aim for total drawdown (bloom to finish) in 4:00-4:30.

"Filter collapsed into the coffee bed"

Cause: Filter wasn't properly seated or water was poured against the filter wall.

Fixes:

• Make sure the three-layer side faces the spout before rinsing
• Pour into the center of the coffee bed, not against the filter
• Pour more slowly — fast pouring creates turbulence that can dislodge the filter

"Coffee tastes papery"

Cause: Filter wasn't rinsed thoroughly.

Fix: Rinse with a full cup of hot water before adding grounds. Pour slowly through the entire filter surface, not just the center.

"No bloom — coffee barely puffs up"

Cause: Beans are past their peak freshness (more than 4-6 weeks from roast date).

Fix: Buy fresher coffee from a local specialty roaster. Fresh beans bloom dramatically. If you're unsure, ask for the roast date when purchasing.

Advanced techniques

The Rao method (continuous pour)

Rather than discrete pour stages, some advanced brewers prefer a single continuous pour after the bloom. After the bloom phase:

1. Pour all remaining water (440g) in a slow, continuous spiral over 2:00-2:30
2. Maintain a very slow, consistent pour rate
3. Aim for total drawdown by 4:00-4:30

This technique produces extremely even extraction but requires good pour control. Master the standard method first.

Temperature by roast level

• Light roast: 205-208°F — denser beans need more heat to extract properly
• Medium roast: 200-205°F — standard range
• Dark roast: 195-200°F — more porous beans extract faster; cooler water prevents over-extraction

Adjusting for altitude

Water boils at lower temperatures at altitude. If you're above 5,000 feet, your water may only reach 200°F at a full boil. Skip the 45-second rest and brew immediately off the boil.

What coffee works best in Chemex?

The Chemex's thick filter makes it uniquely suited for showcasing washed-process coffees — the filter strips out the oils and sediment that can muddy delicate flavors, letting the clean, transparent profile of washed beans shine.

Particularly excellent in Chemex:

• Ethiopian washed coffees — bright acidity, tea-like florals, bergamot notes
• Colombian washed — clean stone fruit, caramel sweetness, moderate body
• Kenyan washed — complex citrus, blackcurrant, tomato savory notes

Less ideal: Natural-process coffees lose some of their characteristic fruit and body when the Chemex filter strips oils. If you love Ethiopian naturals or Brazilian naturals, use a French press or AeroPress where the oils are preserved.

Chemex vs. other pour over methods

Chemex vs. V60:

• Chemex produces a cleaner, more transparent cup; V60 is more nuanced with slightly more body
• Chemex is more forgiving (thicker filters are less sensitive to grind variation)
• V60 gives more control over pour technique; Chemex is more consistent batch to batch
• Chemex scales better for 2+ cups; V60 is optimized for single servings

Chemex vs. French press:

• Chemex: clean, bright, no sediment, oils filtered out
• French press: rich body, more oils, more texture, more sediment
• Use Chemex for washed coffees where clarity matters; use French press for natural-process where richness matters

Tools that make Chemex easier

Gooseneck kettle with temperature control. The most impactful upgrade for Chemex brewing. Pour control is harder with a regular kettle, and temperature precision matters for light roasts.

Scale with timer. Non-negotiable. Pour stages depend on gram-precise water additions.

BrewMark tools:

• Grind Converter — translate grind index 48-56 to your grinder settings
• Brew Calculator — calculate exact doses for any Chemex size or ratio

The Chemex rewards patience and precise pour technique. Get the ratio right (1:16), grind medium-coarse (index 48-56), rinse your filter, and pour slowly in controlled spirals. The result is one of the cleanest, most elegant cups in coffee.