It was an American chemist called Peter Schlumbohm who invented the Chemex brewer and it was released by the Chemex Corporation in 1942. This was at a time when 64% of all household coffee in the States was made using a percolator.
The Chemex brews coffee using the infusion method, which makes it most similar to drip coffee in terms of body and taste. Chemex filters are a little thicker than those used by other pour over methods such as the Hario V60. The result is a slower brew which produces a richer cup of coffee. Although not as rich as the French Press, the Chemex does produce a sediment free cup of coffee that will impress anyone used to the weaker taste of most filter drip coffee machines.
Grinding and dosage
For the grind I always say somewhere between a V60 drip and a Cafetiere is about right. If the grind is too course it will run straight through, giving a weak taste. If it is too fine it will clog up and will result in a muddy taste. Check out our grind guide for more information.
GEEKY ALERT!: For the dosage - a digital scale will help with consistency. Using a 17 to 1 brewing ratio (17 parts water to one part coffee) a Chemex will hold 0.51 ltrs of water for every 30 grams of ground coffee. Or just round it down use 0.5 ltrs of water. Once you know you have the correct amount of coffee and water, you can focus in on perfecting your grind.
Step by step Chemex brewing
1. Heat Water
You will need not only the 0.5 ltrs of water used for the brew but some extra water to rinse the filter.
2. Grind Coffee
Grind 30 grams of coffee. What grind is best? Start with something a little more coarse than drip, but finer than a Cafetiere. Again, see our grind guide for further information.
3. Insert Filter
Place the square filter inside the Chemex.
TOP TIP: The side with the three sections should be just over the Chemex lip used for pouring.
Once the water is warm, rinse the filter and discard the water from the rinse. This helps aid extraction and also serves to pre-heat the carafe.
4. Add Coffee
Place the ground coffee inside the filter.
5. Pour Water
The initial pour is very important. Instead of pouring all the water onto the grounds (as you would with a Cafetiere), only pour enough water to saturate the beans. Chemex states that wetting the grounds allows them to “bloom”. The importance of this step is to get all the coffee in contact with water. After you wet the grounds wait a further 20-40 seconds. During this time trapped carbon dioxide (CO2) escapes from the grounds, this is the bloom and will give you a cleaner and better extracted coffee.
6. Stir (optional)
At this point, you can stir the coffee with a wooden spoon.
7. Add the rest of water
Continue adding water gradually. Don't be tempted to fill it to the very top. Always allow at least an inch of room at the top. Stop pouring the water when you’ve reached your desired amount of coffee. Using a digital scale will prevent you from using too much water.
Once the water has passed through the filter, remove the filter and serve. Don't forget to put you used coffee ground on the garden as they deter slugs (slugs don't like coffee and I don't like slugs!).
Like other manual coffee brewing methods, it is your responsibility to keep any extra coffee warm. Besides chugging the remaining coffee quickly, a good idea is to transfer any extra coffee to a thermal flask for later.