By Mark Prince
You may have never heard of siphon coffee making. Then again, you may have read about it in the New York Times and thought it was some $20,000 gizmo used by crazy coffee nerds in San Francisco. You may have heard of it under a plethora of other names – vacpots, vacuum brewed coffee, siphon brewer, siphon vacuum coffee, and all sorts of word combinations.
This brewing method fell out of favour in the US and Canada by the 1960s, and with only a few holdovers making devices for the next few decades. Most of the major brands that used to make siphon coffee makers eased them out of production during that time, including General Electric, Silex, Sunbeam, Cory and others. Still, the brewing method maintained a hard core set of fans, maybe just in the hundreds, or dozens, and a few manufacturers continued to produce them: Bodum has continuously made a siphon coffee maker since the 1970s. Cona, out of the UK, has been making them since before World War II. Nicro, a commercial small appliances maker, was manufacturing them right up through the 1970s when demand finally disappeared, at least for cafes and restaurants.
In the late 1990s, a bunch of coffee nerds started talking up the joys of siphon coffee makers, or “vacpots”, in places like alt.coffee and with the aid of rudimentary photos and pretty basic short video clips, a new (albeit small) generation of people cottoned on to this brewing method, if not for anything else than the show it provided.
And now, well into the first decade of the 21rst century, and some 160 years after the siphon coffee maker was first invented in France and Germany, the technique is set to explode (figuratively, not literally) with almost everyone in the specialty industry taking interest. Peter Guiliano, the famed green bean buyer for Counter Culture Coffee and acknowledged as one of the best cuppers in the business today, lists the siphon coffee method as one of his favourite ways to make coffee.
Back in 1998, I saw my first ever siphon coffee maker in action. I make no joke about this – it was a seminal moment for me in coffee. I was very much into all things espresso at the time, and I still recall the first time I brewed a cup. I’d been reading about vacpots for a few years – mostly in the newsgroup alt.coffee, but also in books like Ken Davids’ Joy of Coffee – but it wasn’t until I stumbled upon a used Bodum Santos in a flea market that I bought one, took it home and set it up for the first brew.
Almost everything about using a vacuum coffee maker is sensory involved: aromas, fragrance, motion, touch, action. Grind the coffee, add it to the top vessel. Add cold (or hot) water to the bottom. Put the bottom on a heat source. Add the top vessel with its attached siphon. Watch. Liquids defy gravity. The brew gurgles, but it’s not boiling. Remove from heat source. Watch the coffee move back down, or “south”. Watch the bottom vessel’s brewed coffee gurgle as air is drawn through the spent grounds to release the built up vacuum. Remove top vessel. Smell. Ahhh. Pour. Taste. More ahhhh.
So much science. So much sensory involvement. So much fun. And the taste… Do it right, and you’ll wonder not at the fact that so many specialty industry leaders consider this “the best”.
How Do Siphon Coffee Makers Work
A vacuum coffee maker works on the principle of expansion and contraction of gases – actually one gas, water vapour – is what allows the device to brew a full infusion style of coffee and filter the grounds efficiently, leaving a generally clean, pristine cup.
Siphon coffee makers are made up of four parts: the bottom container where the water initially sits and the brewed coffee eventually rests; a top container that has a siphon tube attached to it (and a hole in the bottom of the vessel), where the coffee brewing takes place; a type of sealing material (usually a rubber gasket) to help create a partial vacuum in the lower vessel while brewing is taking place, and a filter, which can be made of glass, paper, metal, or cloth.
There is also a heating source, and there’s usually three types – a cloth-wick alcohol burner (slowest), gas or electric stovetop (faster), or a specialty butane burner (fastest). There are additional heating devices, including the halogen burner system that is part of the $20,000 setup that Blue Bottle Cafe in San Francisco has for their siphon coffee makers.
Once the siphon coffee maker is assembled, heat is applied to the lower container. As it heats up, some of the water is converted to a gas – water vapour. A gas occupies a lot more space than its liquid or solid variant, and it can expand as more heat is applied. Gas can be compressed, but only to a point, whereas liquids do not compress. The water vapour continues to expand and it seeks some relief from all the compression it’s starting to have. The only escape route out of the bottom vessel is the siphon tube traveling up to the top, but the problem is, there’s a lot of liquid blocking its way. So what does the gas vapour do? It pushes the water up the siphon tube!
This is how the brewing water “defies gravity” and gets up top past the installed filter and starts saturating the coffee grounds. Heated (though not boiling) water will continue to force itself up the siphon tube until the vapour gas in the bottom vessel can have direct access to the siphon. By design, all vacuum coffee makers do not have siphons that sit flush with the bottom vessel: there’s always a couple of millimetres of clearance (or more). This leaves some water in the bottom vessel which serves two purposes – protects the glass (if it boiled dry, glass would superheat and could crack), and has a continuing source of water to turn into – you guessed it – more steam, vapour, gas!
This is a desirable thing. Once the water in the bottom vessel is lower than the siphon tube, water vapour starts pouring up the siphon into the top chamber. This does two things – it keeps the liquid all up in the top vessel where the full-saturation brewing is taking place, and it continually heats the top vessel, maintaining near-ideal brewing temperatures (90C and 95C (185F and 204F)). As the vapour bubbles pass through the top liquid, it may appear that the active brewing is “boiling” but in fact it isn’t under normal brewing conditions. If you leave the siphon coffee maker long enough, eventually the top vessel water temperatures will reach 100C, but this takes a very hot heat source and five or more minutes of brewing time in most cases.
Once the brewing time is completed (different sized siphon coffee makers require different brewing times), the heat source is removed and more simple physics take over. Remember that gases expand when heated and that gases also compress under pressure. When heat is removed, the gases start to contract and shrink. Eventually all the gas in the bottom vessel contracts enough that it starts to create a partial vacuum of pressure (negative pressure), and it start pulling the brewed coffee back down, through the filter.
Another thing is going on as well – phase change. Some of the gas vapour starts changing back into its liquid form: water. This is almost like a miniscule turbo boost for the contraction of gas and vacuum forming, aiding the pull of the brewed liquid back down to the bottom vessel. At first it starts slowly, but as you watch, things will pick up speed and unless the coffee filter has been excessively clogged, the last half of the water travel down south will happen twice as fast as the first half did.
The effect is so efficient that once all the liquid has passed back down to the bottom vessel, air is drawn through the grounds up top, drying them out, to fill the vacuum void in the bottom vessel and balance out the pressure to normal room atmospheric pressure. For some, this is how the siphon coffee maker got one of its names – the ground coffee is literally “vacuumed” dry.
How to Use a Siphon Coffee Maker
Enough preamble – here’s the reason you’re reading the article – the visual how-to. This is our preferred method for using a siphon coffee maker, but it is by no means the only way to brew with these devices. In fact, there’s plenty of debate online today by people who have newly discovered these devices, and how different things like stirring techniques, steep times, and even the use of cold vs. preheated water can affect the taste. Some of these theories and practices are interesting to try out, while others seem like a bit of fluffery with no real effect on the cup at best, and a detrimental effect on the cup at the worst.
The most important things to note about using a siphon coffee maker are a) using fresh roasted, fresh ground coffee; b) grinding just before brewing (no wait time in between – so grinding is one of the things you do last); and c) maintaining and monitoring heat during the brew.
You don’t need expensive equipment to make vacuum brewed coffee at home. I do just fine with a $30 Yama 5 cup stovetop model (that includes a nice cloth filter and five spare cloths) as I do with my $150 Hario Nouveau and my $50 butane burner. In this how to, I’m using one of the smallest siphon coffee makers I own – the two cup (8 ounces) Yama “Classic” model. In fact, this is the first time I’ve ever used this particular vacuum coffee maker, part of my collection of over 50 models.
After the visual how-to, We’ll provide some information on the variety of filters available, starting points on how much coffee to use, how long to brew, and how to super-tweak your vacuum brewed coffee experience to get an even better taste for your taste buds.
The Traditional Setup
Here’s a Yama 2 Cup glass and alcohol burner vacpot with a cloth filter and bamboo stirrer. It comes with the alcohol burner, but we’ll be using a butane burner for this how to.
The filter is installed by dropping it in the top vessel, and pulling the beaded metal cord down and hooking it on the bottom of the siphon. This keeps everything in place.
Adding Hot Water
We recommend starting with off-the-boil water to speed things up. You can start with fresh cold water, but in blind tastings, it doesn’t make a difference, as long as the water is high quality.
Hot Water to Begin
Another argument for starting with hot water – if you start with cold water and assemble everything before heating, some water will creep up the siphon long before its temperature is optimal for good extraction.
Add Freshly Ground Coffee
Grind just before brewing – not minutes before. We’re using the amazing Finca Matalapa from Intelligentsia Coffee in this brew. Grind is just slightly finer than drip.
Insert Siphon Vessel
Gently insert the siphon vessel portion into the bottom glass container, taking care to not knock the siphon (it can chip if you’re excessively reckless). Ensure a good seal with the rubber gasket.
Add Your Heat Source
We’re using a small butane burner ($30-$50) which is very efficient and has a controllable flame, which is important for the brewing process. Right now, it’s running on high.
Kick Up Stir, Part 1
As the water starts moving up to the top vessel, give a few stirs to fully saturate the grounds. At this point you also want to lower the flame a bit.
Kick Up Stir, Part 2
Continue stirring to fully saturate and mix the grounds with the water, and further reduce the flame on the burner. The idea is to have just enough flame to keep the water up top, keep the production of some steam or vapour “bubbles” to pass through the brewing coffee. We don’t want the top boiling – just brewing.
With different sized vacpots (and different heating methods), different steep times are required. Because we’re controlling the flame to a minimum for a “gentle” brew, we’re steeping this about 70, 75 seconds.
Removing Heat Source
With a standalone siphon coffee maker, completely remove the heat source (don’t just turn it off) to start the kick down phase. We recommend removing it completely so there’s no residual heat coming up from the burner to slow down the kick down.
Kick Down Begins
As the vapour gas in the bottom vessel starts to contract, shrink, and change back to water, it creates a partial vacuum of negative pressure, and pulls the brewed coffee through the filter back to the bottom vessel.
Kick Down Almost Complete
The kick down is almost complete, and things have sped up a bit. Some recommend wrapping a wet cloth around the bottom vessel to speed up the kickdown further, but we do not recommend this – it can result in cracked and imploding glass.
At the end of the kick down, air is sucked very rapidly through the spent coffee grounds to fill the vacuum in the bottom vessel, resulting in bubbling and turbulence. This is the indicator that your brew is done.
Removing the Siphon Vessel
At this point, you can carefully remove the siphon vessel portion of the vacpot, placing it in the lid / built in stand.
Ready to Drink
Your siphon coffee maker experience is done, and you’re ready to enjoy some fantastic coffee!
What Kind of Filters Exist for Siphon Coffee Makers
When you buy a new siphon coffee maker it comes with a filter, and usually some replacements for the filter material. There are a wide range of filters that have been made in the past and are continued to be made today, and many of them can be used to replace the filtering device that came with your brewer if you’re not happy with it. Here’s a breakdown of the most common filters available today.
Cloth (with ceramic and/or metal shaper and spring): sometimes a double piece of cloth material – one piece has a coarse, heavy thread makeup, the other piece has more of a felt, fine threading. These are usually circular, with a stitching on the outer edge and a tie string looped through in order to secure the filter to a ceramic or metal part that acts as the “hard part” of the filter at the top of the siphon tube. Cloth can be used up to a hundred times or more, with care, and cloth filters can be fairly easily obtained.
Some believe you get the best overall cup from a clean cloth filter (as compared to other filters) because unlike paper, cloth filters allow the most volatile oils from the coffee grounds to pass through.
My cleaning regimen for cloth filters has changed over the years. Cloth filter assemblies should be cleaned right after use with a soft brush and running water, and then soaked in a solution of oxyclean and boiling water. Rinse well after, and store dry.
This will not harm the cloth like bleach will, and it comes out sparkling white and odor free.
Paper (with plastic and/or metal shaper): The Hario Nouveau siphon coffee brewer (and other brewers) uses a steel holder/paper combination that is effective and fairly efficient. It can be purchased separately as well. You end up with a coffee filtered in the same method as auto drip, which is a detriment to some because paper can impede some of the more volatile oils and aromas from passing through into the final brew. But hey, you’re brewing at optimum temps with a vac pot, and most auto drip owners can’t say the same. Cleanup is easy – remove filter, rinse over the sink (or shake over the garbage can), untwist the top plastic clamping disc, drop the paper filter, rinse plastic once more, done.
Glass: All glass filters are available to this very day if you can find them – the Cona Glass Rod Filter. But they weren’t the first. A now-defunct but major American appliance brand named Cory made their reputation partially on their “Cory Glass Rod” which ironically was originally created for tea brewing, not coffee. They modified the original Cory Glass Rod, calling the original name of “Cory New Glass Rod” after optimizing its size and shape for coffee brewing. The device is a long glass tube with a bulbous, rough middle. The Cona rod is very similar in shape, but better made. These glass rods sit inside the siphon tube with the bulbous part acting as the filter at the top of the tube. The rough (but not sharp) surface of the middle was the filter – coffee grounds would get trapped in the little channels between the bumps, but liquid would still pass through. In practice, these glass filters allow a fair amount of sediment to pass into the brewed coffee. Some find this beneficial, others do not.
In addition, my experience has been that these glass rods do not work well in smaller siphon coffee makers (3 cups or smaller): the turbulence and lower water volumes allow the rods to bounce around a bit, letting a lot of ground coffee pass through to the vessel below.
Nylon Mesh: Several electric siphon coffee brewers, including the (now defunct) Black and Decker Infuze, or the Bodum Electric Santos, use a one piece filter assembly that has nylon mesh inserts to allow brewed coffee to pass through. These are fairly effecient designs, letting more coffee oils pass through than paper does, but they are quite fragile and easily torn. Cleanup is pretty easy – some are rated as dishwasher safe.
Rare and No-Longer-Manufacturered Filters
I also wanted to cover some other filtering devices that are either quite rare today, or no longer manufactured. Some of these devices are quite efficient at what they do, and hopefully will make a comeback.
Metal (non mesh): Some believe this is the best filter ever created – the Nicro metal filter. It consists of two shallow bowl discs with cutouts on them (cutouts are offset to each other), a center spine that perforates both bowls, and a chain and spring loaded device to secure it to the bottom of your syphon filter. It does let more sediment pass compared to cloth or paper. Cleaning: a no brainer – rinse, dry, drop in dishwasher, whatever. This is the main reason why people love it so much – easiest filter to clean, and still brews a great cup of cup of coffee.
Metal Mesh: These were found in the Sunbeam vacuum brewers from the 1940s and 1950s – models like the C30B used a fine mesh filter as part of their filter assembly. The mesh was a finer web than the typical mesh found in press pots (like Bodums), but they still let a bit more sediment pass compared to non-mesh metal filters or cloth or paper. These filters are circular, with a thin steel spoke frame and rubber around the outer edge.
Glass and Metal: Silex, probably during WWII to fight off shortages, came out with their glass and metal “Silex Lox-In” filter. This was also designed to combat a problem Cory rods had – dancing around and letting grinds pass to the bottom. The Silex has a similar design to Cory rods on top – a spike with a bulbous, rough end, but the bottom was a spring and catch for attaching to the bottom of a syphon tube, thereby (in theory) keeping the filter secure. I say in theory, because I own three of these filters, and all three are terribly designed – part of the bulbous middle part has a seam of solid glass (no rough bumps) and as a result each of them allow a lot of grinds to pass through to the bottom vessel.
On the left is a butane burner which fits most standalone siphon coffee makers. On the right is the standard cloth wick alcohol burner they typically ship with.
When it comes to heating the water in a siphon coffee maker, you usually have two options with some sub-options: either the vacpot is designed for stovetop (electric or gas) use, or for a self-contained heating device like an alcohol wick burner or a butune burner. The shape of the bottom vessel usually tells the tale – if it’s flat, it is designed for stovetop use. If it is round, it’s designed to hang above a heating source.
My preferred heating method by far and away is the specialized butane burner. Some siphon coffee makers usually sell a variant of this, costing anything from $25 up to $60 or more. You can also find these at science stores and woodworking specialist stores. Look for one that has an easily controllable flame – that’s crucial to great siphon coffee.
Alcohol burners are pretty basic and slow. If you don’t use the right type of burning alcohol look for “soot free” denatured alcohol, ethyl or an ethyl / isopropyl mixture that’s high on the ethanol side – isopropyl alcohol (rubbing alcohol) tends burns hotter than ethyl or methyl alcohols, but also burns orange and produces a lot of soot. Soot doesn’t make the vacpot “show” very appealing.
A more recent method is the “halogen burner” system pioneered in Japan with Hario and other manufacturers. These are, in essence, a high wattage (up to 400W) halogen bulb controlled by a dimmer switch. The bodies are fancy and allow for the claw feet of a siphon brewer to sit on an elevated base, with the halogen lamp encased by a grid screen and covered with a red quartz lens (so as not to be too bright). These are nice for show, but slower than butane burners. They do however provide a more gentle heat action.
Grinding and Timing Basics
When it comes to the coffee and the grind, I grind based on the filtering material. If I’m using cloth filters, I tend to grind fine – a fine drip grind or even finer. If I’m using paper, just a normal drip grind is good. If I’m using all metal or glass filters, then I grind a tad coarse. Experiment with your grind to find what works best for you.
Everyone should grind literally seconds before brewing. I’ve seen videos of siphon coffee “experts” walking people through the art of using a vacpot, only to see them grab preground coffee from a container. They may be siphon coffee maker experts, but they’re not coffee experts. Fresh grinding is crucial to a great cup.
This leads me to “timings” All sorts of timings. First timing I want to talk about is the decision on how fast or slow you want your vacpot coffee. If you want it fast and efficient, preboil your water, or use a hot water tower to supply the water used for brewing. If you want to do a brew from cold, fresh water, first fill the bottom vessel with water up to the cup line, and place your heater (preferably the butane heater) underneath and open it up wide, full flame. For 3 cup models, it will only take 3 minutes or less to get the water up to about 75C. You can tell this visually when you start seeing scant whiffs of steam coming off the coffee: it’s not boiling yet, but it’s getting there. Reduce the heat at this point (or remove it temporarily), and grind your coffee. I like using about 8g per “cup” (usually 1 “cup” on siphon coffee makers = 4 US fluid ounces). add the coffee to the assembled top vessel (with the filter in place), and then carefully wedge it into the bottom vessel.
Reapply the heating source, and watch the water start to slowly climb up the siphon. Why do we put the top vessel on only after the bottom water has heated up about 75% of the way? Because this brews a better coffee than if you ground the coffee and assembled everything before first applying heat. If you do it from a cold start, some water will start snaking its way up to the ground coffee by the time the bottom vessel’s water temperature is around 75-80C – this leads to poor initial extraction, something that can degrade the final brewed cup of coffee. You want the initial water that hits the ground coffee to be very hot – 90C or higher. This helps prevent the extraction of excessive sour tastes, and also aids in keeping the caffeine extraction down by 5-10%. (Caffeine = bitters in the cup).
As the water climbs up the siphon, start adjusting your heat source lower – you want it so that, when all the brewing water is “up north”, you have just enough flame to maintain a tepid boil in the bottom – nothing raging or turbulent. This helps again with maintaining a great brewing temperature. If you’re brewing on the stove, do the same thing – if you had your stove set at 7 or 8, turn it down to 3 or 4 on the burning element, or even lower – whatever’s need to just barely maintain the boil and production of water vapour.
How long should you brew for? It’s personal preference – the longer the brew, the stronger (and more bitter) the coffee will be. I like to give 2 and 3 cup siphon coffee makers about 70 seconds of full infusion time – 70 seconds after the last of the water “travelled north” up the siphon tube, I remove the heat source completely. For 5 cup models, a bit longer is good – probably 90-120 seconds (up to 2 minutes). And for 8 and 10 cup models, I give about a full 3 minute infusion time, depending on how controllable the heat source is.