Two glass globes stack on a stand with a tube running between them and a flame underneath. Water climbs uphill into the top globe, coffee comes back down into the bottom one, and anybody standing in your kitchen stops talking until it's over.
The siphon also makes one of the cleanest cups you can brew at home. Coffee steeps in full immersion at the top, then passes through a fine filter on the way down, and very little else gets you both.
So why does so much siphon coffee disappoint? Usually because of three habits taught in almost every set of instructions, including the ones that came in the box with your brewer. We brewed the same pot over and over on a five-cup Yama, weighing the water going in and the coffee coming out, checking temperature at every stage, and reading the results with a refractometer. The recipe below landed at 1.42% TDS and 19.9% extraction, which is where coffee tastes the way it should.
How a Siphon Coffee Maker Works
The siphon, also called a vacuum pot or vac pot, moves water with pressure instead of gravity or a pump.
When you heat the water in the sealed lower globe, steam forms above it and has nowhere to expand. It presses down on the water and pushes it up the tube into the upper chamber. A little water always stays behind in the lower globe, and you'll want to remember that, because it does more work than you'd expect.
Cut the heat and the steam condenses back into liquid. All that steam collapses into a few drops, the pressure inside the lower globe falls below the pressure of the room, and the atmosphere pushes down on the open upper chamber and sends your coffee back through the filter.
Water moves toward whichever side is pushing less. Heat the globe and the inside pushes harder, so the water climbs. Cool it and the room pushes harder, so the coffee drops back down.
What You'll Need
- A siphon brewer. We tested on a five-cup Yama, which holds about 23 ounces despite what the name suggests.
- A metal filter to replace the cloth one that came with it
- A kettle or dispenser that holds at least 24 ounces of hot water
- Burr grinder
- Gram scale
- Thermometer, at least for your first few brews
- A stirring paddle made of wood, plastic, or silicone
- Fine-mesh strainer for cleanup
- Your smallest burner, or the burner that came with the brewer
- Freshly roasted whole bean coffee
Skip the metal spoon. Metal utensils scratch hot glass, and the paddle from an AeroPress works well if you already own one.
Siphon Coffee Ratio and Grind Size
Use a 1:16 coffee-to-water ratio by weight, the same ratio that works across nearly every brewing method. You may run across older siphon advice calling for a much stronger dose, sometimes 2 grams of coffee per ounce of water. We tested it and found no reason for the exception. At 40 grams of coffee to 627 grams of water, extraction came in at 19.9% and the cup tasted balanced.
Grind coarse. On a Baratza Encore, start at setting 30, which puts you in French Press territory, not drip.
If that sounds too coarse for a brewer with a fine filter and a one-minute steep, the reason is temperature. A siphon holds your water at roughly 205°F for the whole immersion, longer than almost any other method sustains that kind of heat. Hot water pulls flavor fast, and a coarse grind slows it back down.
Not sure where your grinder lands? Our coffee grinding guide walks through particle size across every brewing method.
Step-by-Step Siphon Brewing Instructions
- Fill the lower globe to the 5 cup line with 200°F water. Start hot, never cold.
- Secure the metal filter in the upper chamber, hook the chain, and press the upper chamber into the lower one until the gasket seals.
- Set the brewer on your smallest burner at medium heat.
- Watch the water rise into the upper chamber, then wait for it to reach 205°F. Expect one to three minutes.
- Turn the heat down as the water gets close. This slows the last stretch and keeps the brewer from bouncing around on the burner.
- At 205°F, add 40 grams of coarsely ground coffee. Stir about ten seconds, just enough to wet every ground.
- Just before the one minute mark, give it five strokes to sink any grounds still floating on top, then cut the heat.
- Slide the brewer onto an unused burner or the counter. This speeds up the drawdown.
- Drawdown starts after about a minute and takes another 90 seconds. You'll know it's finished when the coffee in the lower globe stops bubbling.
- Wiggle the upper chamber free, rest it in the stand, and pour. Your coffee will still be at least 190°F.
Total time from flame to pour is about six minutes.
Three Mistakes That Ruin Siphon Coffee
1. Starting With Cold Water
Water that starts cold has to climb to brewing temperature on the burner, and you pay for every one of those minutes in evaporation and waiting. Cold starts are the main reason siphon brewing has a reputation for taking fifteen minutes.
Watch out for heat loss on the way into the globe. Our dispenser is set to 200°F, and by the time that water passed through a pitcher and into the glass it measured 170°F. Aim higher than your target and use as few containers as you can.
2. Adding Coffee Before the Water Arrives
Plenty of siphon instructions tell you to load the grounds at the start. Don't. Two separate things go wrong.
You lose track of your brew time. Water doesn't arrive all at once. It starts creeping up the tube as soon as there's pressure behind it, so extraction begins the moment the first water touches your grounds, at whatever temperature it happens to be, and keeps going for as long as the climb takes. In our testing, the stretch between a full upper chamber and 205°F ran anywhere from one to two and a half minutes, and that's after the water finished rising. Load early and you could be several minutes into extraction before your brew officially begins. That carefully timed one minute steep is now one minute plus a number you never wrote down.
You also lose flavor before you start. Grounds sitting in an empty upper chamber are suspended in glass directly over boiling water, heating up with no liquid to carry that heat away. The coffee bakes, aromatics escape, and then the first water to reach those grounds is the coolest water of the whole brew.
Let the water get up there first, then add your coffee.
3. Stirring Too Much
Stirring moves extraction further than grind size or brew time in a siphon, and most people never think of it as a variable at all. Our early tests used about thirty seconds of stirring plus a second stir and produced 23.6% extraction, past the point where coffee starts tasting harsh. Cutting back to ten seconds up front plus a quick five-stroke stir brought it to 19.9% at the same grind and dose.
Heavy stirring causes a second problem too. It pushes fine particles into the filter, which slows your drawdown or stalls it completely.
How to Tell When the Water Hits 205°F
Timing the climb won't work, because it depends on your burner, your starting water temperature, and your altitude. Our own runs varied by more than a minute using the same equipment.
Watch the water instead. Below brewing temperature it bubbles. At 205°F the bubbling backs off and the surface turns into a roll. The change is obvious once you've seen it happen.
Use a thermometer for your first few brews and pay attention to what the surface looks like when it reads 205. After that, your eyes will do the job.
The water arrives cooler than you'd expect because it never boiled. It only needed enough steam pressure beneath it to make the climb, and that happens well below 212°F. We measured water arriving in the upper chamber at 180°F. What heats it the rest of the way is that small amount of water left behind in the lower globe, still over the flame, still making steam and pushing heat up the tube.
Fresh Coffee Floats, and What to Do About It
Coffee within a few days of roast still holds a lot of carbon dioxide. In a siphon, that gas lifts the bed into a mound that rides on top of the water instead of sitting in it, and coffee floating above the waterline isn't brewing at all.
Brewing with coffee three days off roast, we watched the bed dome up right after the grounds went in and come close to breaching the top of the chamber. Around 45 seconds the mound settled a little, and that's the moment to sink it with a short stir.
Most siphon guides mention a mid-brew stir as an optional touch for even extraction. With very fresh coffee, count on needing it. That stir is what gets the whole dose brewing.
This shows up far more with coffee roasted to order than with coffee that's been sitting on a shelf. Our guide on how to keep coffee fresh covers what's happening inside the bag.
Controlling the Drawdown
Your coffee keeps extracting the whole time it drains through the filter, which makes drawdown part of your brew time whether you count it or not. Most siphon recipes quote a steep time measured from grounds-in to heat-off and skip right past the two or three minutes that follow.
You can control it. Leaving the brewer on the burner it was heated on gave us a two minute drawdown. Moving it to an unused burner right after cutting the heat brought that down to a minute and fifteen. The glass cools faster, pressure drops faster, and the coffee finishes draining sooner.
That's roughly 45 seconds of extraction you can remove any time your cup is coming out too strong.
You'll know drawdown is done when the coffee in the lower globe stops bubbling. The spent grounds come out nearly dry, which is why a siphon returns more of your water than most brewers.
Heat Control and the Dancing Brewer
Once your coffee is in, aim for a calm roll. If large bubbles are breaking hard across the surface, turn the heat down.
A gas burner on medium was enough to make our flat-bottom brewer vibrate across the stovetop and start drifting off center, and we ended up holding it in place. That's more excitement than anyone needs from a glass vessel full of 205°F water. Turning the burner down solves it.
If your siphon came with an alcohol lamp, you'll find you can't adjust it once the brew starts. Wick length, trimmed before you begin, is your only control. A butane burner or halogen beam heater puts a dial in your hand, and it's the most useful upgrade available for the method.
One safety note whatever your heat source: never let the lower globe boil completely dry. That last bit of water is what keeps the glass from superheating.
Best Coffee Roast for a Siphon
Hold any coffee at 205°F for a full immersion and a dark roast turns bitter. Siphons strongly favor light and medium-light roasts, which have room to take that much heat and enough character to fill out such a clean cup.
Washed coffees with floral and fruit character do especially well. A siphon takes out nearly everything except flavor, so delicate notes that get buried in other brewers come through clearly.
We ran our tests on a medium roast, partly to confirm the method holds up outside its ideal range. A lighter roast may want a slightly different grind. Start at the same coarse setting and let taste tell you whether to move.
Siphon Cleanup
Give the upper chamber about ten minutes to cool before you handle it.
Tap as much of the spent coffee into the trash as will come loose, then scrape out what's left with a wooden utensil or a silicone spatula.
Leave the filter clamped in place, hold the chamber over a fine-mesh strainer, and rinse the inside out into the strainer. Coffee grounds should never go down your drain.
Take out the metal filter, rinse it, and let it dry.
Still using the cloth filter that came with the brewer? It has to be stored wet in a sealed bag in the refrigerator between uses or it will sour. That alone is reason enough to switch to metal before your first brew.
Is a Siphon Worth It?
If you don't already own one, spend the money elsewhere. An AeroPress makes excellent coffee faster, with fewer variables to manage and nothing that can shatter. A French Press costs less and takes less practice.
If a siphon is already sitting in your cabinet, save it for mornings with nothing scheduled. Six minutes of brewing gets you a remarkably clean cup, and watching it work never quite gets old.
Frequently Asked Questions About Siphon Coffee
What grind size should I use for a siphon coffee maker?
Use a coarse grind, similar to what you'd use in a French Press. On a Baratza Encore, setting 30 is a good place to start. A siphon holds water at roughly 205°F for the entire immersion, and that sustained heat extracts quickly, so a coarse grind keeps your extraction in the right range.
What is the correct coffee-to-water ratio for a siphon?
Use 1:16 by weight, the same ratio that works for most brewing methods. Our testing used 40 grams of coffee to 627 grams of water and produced 19.9% extraction, near the center of the ideal range. Older siphon guidance calling for a much stronger dose didn't hold up when we measured it.
Should I put the coffee in the siphon before or after the water rises?
After. Adding coffee before the water arrives starts extraction at an unknown time and temperature, and it bakes your dry grounds in a chamber suspended over boiling water. Wait until the water has risen and reached 205°F, then add your coffee.
How long does siphon coffee take to brew?
About six minutes from lighting the burner to pouring, as long as you start with hot water and move the brewer to a cool surface for the drawdown. Starting cold and leaving it on the burner while it drains can stretch that to fifteen minutes.
How do I know when the water is hot enough to add coffee?
Below brewing temperature the water bubbles. At 205°F the bubbling backs off and the surface shifts into a roll. Use a thermometer for your first few brews to learn what that change looks like, then rely on your eyes.
Why is my siphon coffee bitter or harsh?
The usual causes are stirring too much, grinding too fine, or using too dark a roast for the method. Stirring affects a siphon more than most brewers, so cut back to about ten seconds up front plus one short stir mid-brew before you change anything else.
Why did my siphon coffee stall during drawdown?
Too much stirring pushes fine particles into the filter and creates a barrier your coffee can't easily pass through. Grind coarser and stir less. A clogged or poorly seated filter will do the same thing.
Can I use a siphon on a kitchen stove?
Flat-bottom siphon brewers are made for stovetop use. Use your smallest burner so the flame stays within the footprint of the glass. Round-bottom siphons that sit on a stand are built for a small dedicated burner and aren't meant for a kitchen range.
Ready to Brew
A siphon needs your attention more than it needs expensive gear. Start hot, wait for the roll, add coffee after the water arrives, stir sparingly, and move the brewer to a cool burner for drawdown. Those five decisions account for nearly all the difference between siphon coffee worth the wait and siphon coffee that isn't.
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