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Peter Schlumbohm invented a lot of things, but he was absolutely fanatical about refrigeration systems. His pursuit of refrigeration and how to improve it through chemical, mechanical and engineering processes occupied most of his life’s work.
Which led to the invention of a coffee maker.
That coffee maker is the Chemex Coffee Brewer. You see, while Schlumbohm was obsessed with refrigeration, he did invent a lot of things, and one of them was the Chemex coffee maker, which he initially designed in 1939. It was improved in 1940 and improved again in 1941 when it finally was manufactured and sold.
The Chemex is the second oldest, continually sold pour over coffee system after the Melitta system. It’s quite different from the Melitta — or the Hario system — when you get down to the nuts and bolts of it all, as we will do in this How To on the Chemex Brewer. We will dive deep into this history later on, but we want to show you how to use this brewer first!
This How To is part of CoffeeGeek’s Pour Over Event, which is brought to you by Bonavita World and Baratza. For this how to, we’re using Bonavita’s budget-friendly 1.0 Litre Stovetop Gooseneck Kettle ($25) with Baratza’s entry level Encore White Grinder ($140). While we show photos of a vintage (1950s!) Chemex 10 Cup brewer (with hammered glass), for the How To, we’re using the much more budget-friendly 8 Cups Glass Handle Chemex ($45). Of course, we’re using the unique Chemex Square Filter papers as our filtering method. And we’ve chosen an amazing coffee from Batdorf Coffee, their Ethiopian Sidamo Guji, which sadly is very seasonal and no longer available this year (it was beautiful).
How to Brew with a Chemex Brewer
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At first glance, you might think the Chemex works the same way as a Melitta brewer, or a Hario system. But the unique design of the brewer, the extra thick filtration paper, and its configuration of 3 layers of filter paper on one half side of the cone it forms, and 1 layer on the other, all need special care and attention to deliver a superior cup of coffee.
Melitta systems have small ribs inside the filter holder to allow for coffee extraction out the sides of the filter paper as well as the bottom of it’s flat angled point. The ribs also allow some air to escape from the brewing chamber though this isn’t a big “need” with Melitta brewers because there’s usually air gaps between the filter holder and the vessel the coffee is brewed into. Hario systems also have concentric ribs that serve the same purpose.
Chemex is unique in that it is a one piece design and flat glass all around the filter holding area, save for the chute in front of the brewer that you pour coffee out of. If that chute becomes blocked by the filter paper welding itself to the contours of the chute, a seal to the lower chamber will be created, not allowing air to easily escape from. Also, because there’s no way for coffee to freely flow out the sides of the filter paper where it rests against the flat glass of the top chamber, almost all the coffee is extracted through the bottom of the filter cone, down below the narrow neck of the Chemex brewer.
This design makes the Chemex very different from a Melitta or a Hario system. First, your brew times will be longer. Second, you cannot use as fine a grind as you would in an auto drip brewer or a Hario manual pour over system. In fact, as much as we refer to an “espresso” grind, or a “drip grind” or indeed, a “Hario” grind, we really should refer the unique requirements of this brewer grind fineness as a “Chemex grind”. Then there’s a third issue. One needs to observe the filter and ensure the gap between filter paper and the pouring spout chute remains clear of the filter paper material.
There are other considerations too. For example, there seems an equal number of Chemex brewer aficionados who argue both for and against stirring the coffee slurry during the brew. Also, a popular coffee roaster — in their Chemex brewing how to — advocate not even letting all the coffee actually brew into the bottom of the vessel (they suggest removing the filter with it’s still half-full slurry of water and coffee once you brew about 2/3s of your total water volume).
The CoffeeGeek method — which we’ve used since about 2002 with very little modification, and is based on discussions with actual Chemex representatives of that time — aims to deliver the best possible cup with very simple and easily repeatable brewing methods on the Chemex brewer.
Let’s talk about how much coffee to use. Chemex advises “1 rounded tablespoon per 5 ounces brewed”. In metric, that is roughly 8.5g (a level tbsp is 7g) per 150ml of coffee desired. That is 1g of coffee per 17.5ml of water, or a ratio of 1:17.5. Put another way, it’s 5.75g per 100ml brewed. This is one area we differ from Chemex, and it could be due to Chemex basing this ratio on much darker roasts than are the norm today.
At CoffeeGeek, we advise using a ratio of 6.5g of coffee per 100ml of water used, and we grind it about 3 clicks coarser than our normal pour over grind (on the Baratza Encore grinder). The grind looks like slightly fine kosher salt. The grind, being coarser, requires a larger dose than Chemex’s 75 year old recommendations. It also needs to be a larger dose because of modern roasting techniques and roasting levels. Based on this, because we’re brewing a 700ml batch for this How To, we’re using 45.5g of coffee.
For this How To, you will need:
- a Chemex Brewer (we’re using an 8 cup glass handle model for this demonstration)
- good, freshly roasted coffee
- a quality grinder
- a scale — even a budget scale like the $16 one we’re using here
- a pour over kettle
- a timer (your smartphone will do)
- optionally, a chopstick or a stir stick. The chopstick is a trick some use by placing it in the Chemex before brewing, so it creates a barrier to the filter paper, preventing it from sticking to the Chemex’s pour chute.
The Steps to Brewing Chemex Coffee
History of the Chemex
As mentioned in the preamble, Peter Schlumbohm was a prolific inventor, but his life passion was — believe it or not — refrigeration. He was absolutely obsessed with inventing a cheaper, more efficient, smaller way to create and install refrigeration in every household. It would probably pain him if he were alive today to see that he’s entirely known for his Chemex coffee brewer invention.
The Chemex did come out of his dream for better refrigeration. He believed he was headed to a serious breakthrough on it in 1939, but didn’t have the money to make it realise. He sought out investors and could only find people who would take half of his inventions and half of his company and profits. That didn’t suit Schlumbohm, so he turned to his other, minor inventions and patents. In his words, “To afford that refusal (of the businessmen who wanted half of his refrigeration invention), I had to take an appraising look at the other arrows in my quiver. There was this new patent for the coffeemaker, with its broad appeal. Within a week, I had sold half-an-interest in it for $5000 and planned to license it.”
After going through wartime hoops, the Chemex Corporation was up and running by 1942, and Corning Glass Ware was contracted to manufacture the first units. Besides designing the brewer, Schlumbohm was also its primary marketer; his strength of will and persuasion convinced giants like Macy’s to sell the brewer, almost from day one.
The Chemex gained immediate popularity. It’s design embodied the Bauhaus style ethic, which was immensely popular during that time period. Being made entirely of glass and wood (no metals), it resonated during a time period when all metal was being directed towards the US war effort. In 1942, the Chemex brewer appeared on the cover of the Museum of Modern Art’s ‘Useful Objects in Wartime’ bulletin, and entered into the Museum’s permanent collection.
About the design and filter
Schlumbohm recognized — in early prototypes — that there had to be a good air channel in his one piece design to achieve a good brew of coffee. Initially, his patents showed very complicated venting systems in the design, but he settled on a very simplistic exaggerated pouring spout and chute that would double as an air channel.
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The middle collar of the Chemex was designed to fit all hands — small and large — and went through a lot of testing to find this happy middle ground. Even the choice of wood and the wood’s finish was taken into account to make it comfortable to hold.
You may notice that all Chemex brewers have a little “bump” or button on the front lower chamber, below the spout. On all models except for the 3 cup models, this button indicates the half-volume brew measure. The full measure is just below the collars. The button on the 3 cup model is the “full measure” amount, or max brewing volume for those brewers.
The borosilicate glass used is flame resistant, so it can actually be kept on a low flame on a gas stove to keep the coffee warm or hot, and was advertised as such early on in the product’s life. If used on an electric stove, a steel trivet must be used between the Chemex and the electric stove coils. I have a late 1950s vintage 10 cup Chemex brewer and it’s glass is very unique: it has a hammered effect on the glass (shallow dimples) and is lighter than the current day Chemex 10 cup model, so over the years, they have changed the glass.
Schlumbohm really spent a lot of time on the filter paper. He discovered that using thicker paper lead to less acidic (less bright) coffees that didn’t upset stomachs as much for those sensitive to that kind of thing; he didn’t know it also reduced the coffee oils making it to the cup, thus reducing the cholesterol extraction from the coffee, but it does, and some see that as a benefit to this day. He also came up with the 3 sides / 1 side filter design for a very practical reason: by having 3 filter paper layers on the spout side of the brewer, it all but eliminated the paper from shaping and adhering to the filter chute area, which meant no problems with air locks in the bottom chamber.
Chemex Tips and Tricks
There’s a lot of advanced tricks and techniques you can use to get a better cup of coffee out of your Chemex, but to be honest, just following the How To above will deliver a fantastic cup: these additional tricks and tips will — at best — only marginally improve your coffee.
The most important tip is to always keep that pour chute clear of the filter material. If it seals up, your brew will stall and be ruined. Some folks like to put a chopstick right into the Chemex (a sanitized clean one) and let it rest in the pour chute; this way, the filter paper has no chance of adhering to the chute area.
We like the 6.5g/100ml ratio of coffee to water in the Chemex, but others have used as much as 7.5g or even 8g per 100ml, and swear by the cup quality. Definitely experiment to see what works best for you, keeping in mind that darker or lighter roasts can benefit from higher or lower doses. Also experiment with the grind fineness, but never, ever use grind as fine as you would use in a Hario; the thicker filter paper, tied with the tight seal of filter paper to the entire upper chamber (except for the chute area) will lead to a clogged, stalled brew in your Chemex.
Lastly, you can use metal filters in a Chemex, like the popular Kone filters, but the Chemex Corp themselves advise against this. Here’s what they have to say: “The paper filters are based on laboratory grade paper and designed specifically to filter out impurities, all unhealthy and bitter elements from the coffee. By using Chemex filter papers one is able to brew coffee as strong as they like, without acidity and bitterness. It is a misconception that metal filters provide a “stronger” cup of coffee, when in fact the coffee produced simply has leftover flavor of the oils and sediments that actually detract from experiencing the full flavor of the beans.”
Our take at CoffeeGeek is the oils blocked by paper filters are actually beneficial to the final cup taste and quality, and should not be dismissed. Chemex’s reason for being is in part the cleaner, less acidic cup. If you want a true Chemex brew, use the paper filters. If you want a fuller, more balanced cup, consider a metal filter like the Kone.
This Chemex How To is part of CoffeeGeek’s Pour Over Coffee Event, a series of articles and how tos, wrapping up with a Master Class on Pour Over Coffee. We’re also throwing in a contest, thanks to two amazing sponsors (Baratza and Bonavita) we have lined up.
For this Chemex How To, we used Bonavita’s budget-friendly 1.0 Litre Stovetop Gooseneck Kettle ($25), which helps bring a home pour over setup to even the most frugal of budgets.
We used Baratza’s entry level Encore White Grinder ($140) for our Chemex How To. This is one of the best bang for the buck grinders out there, and while $140 might seem a lot to some, in the realm of specialty coffee, it’s an absolute steal at that price, considering the performance it delivers, and the after sales service you get on it.
While we show photos of a vintage (1950s!) Chemex 10 Cup brewer (with hammered glass), in parts of the How To, we’re using the much more budget-friendly 8 Cups Glass Handle Chemex ($45). Of course, we’re using the unique Chemex Square Filter papers as our filtering method. And we’ve chosen an amazing coffee from Batdorf Coffee, their Ethiopian Sidamo Guji, which sadly is very seasonal and no longer available this year (it was beautiful).
See our other Guides and How Tos