Cold Brew Coffee

Cold brew definitely tastes different to hot brewed coffee that has been chilled. Some compounds in coffee are only soluble in high temperatures and therefore they don’t get extracted. Typically people call cold brew ‘less acidic and less bitter’. That can be a good or bad thing, depending on the coffee.

I use the same grind I use for filter coffee. Some people go as coarse as a french press grind. Apparently it’s better to use coffee that is a couple weeks past roasting to let it degas. You definitely want it freshly ground, though.

I use a 1:11 coffee to water ratio, which is ready to drink. Some people make a stronger concentrate like 1:5, then top it up with boiling or cold water for either hot or cold coffee. I tried this once and topping it up to 1:11 tasted watered down.

The only challenge with cold brew is filtering.1 You can essentially put the coffee and water together and leave it for 12–24 hours. After brewing it’s almost impossible to filter more than 300–400 ml through a paper filter before it gets clogged. My theory is that the total dissolved solids are high enough to block the filter even if the liquid looks almost clear.

I landed on what I think is an effective and simple solution: a cotton sack. The cotton is fine enough to filter coffee fines but it let’s liquid through. I bought a product called a CoffeeSock. They come in different sizes but I got the 64 oz version that fits perfectly in a 2 quart (almost 2 liter) wide mouth mason jar. They sell the jar and sock as a kit. I also got a lid for the jar that makes pouring easier.

155 g medium ground, medium roast coffee
1,700 ml cold water
  1. Measure out 155 g of coffee beans and grind medium-coarse.2
  2. Put the CoffeeSock inside the jar, folding the top over the rim, and fill with ground coffee.3
  3. Pour 450 ml of water over the coffee and let it bloom for a minute.4
  4. Pour in the remaining water (1700 ml should fill the 2 quart jar), tie up the top of the sock and put the lid on the jar.
  5. Leave it for 12–24 hours at room temperature.5
  6. Pull the sock out of the liquid. Give it a little squeeze to help it drain, but don’t use much force.
  7. Tip the coffee grounds out of the sock and rinse it under the tap.
  8. Pour your coffee through the sock one more time to filter out the small amount of fines that got through during brewing.
  9. Refrigerate until chilled.
  10. I serve it straight up or over ice. A splash of cream is sometimes nice.

  1. Before I found the CoffeeSock I tried a fine mesh filter that was sold as a coffee filter but this wasn’t fine enough. I almost bought a vacuum filtration kit but the sock seems like the perfect tool for the job. ↩

  2. This is a 1:11 coffee to water ratio. If you have a different container size just fill it most of the way to the top and divide the weight of the water by 11 to get your coffee weight. E.g. 1200 g/ml water—divided by 11—is 110 g of coffee. Or if you have a set amount of coffee, multiply the weight by 11 to get your water weight. ↩

  3. The CoffeeSock is made for brewing in. It does a good job because it also keeps the coffee suspended in the water. But if you wanted to make a big batch you could simply mix the coffee and water in a large container to brew then use the sock (or some other fine cotton) as a filter. ↩

  4. I use a 1:2 to 1:3 coffee to water ratio for the bloom. I tried using off the boil water for the bloom to bring out some more acidity. It definitely impacted the flavour and the result was nice—still closer to cold brew than chilled coffee. But I’d like to do a side by side to see whether I want to keep trying this. ↩

  5. It’s pretty hard to over extract coffee with cold water. I’ve found it tastes pretty similar after 12 and 24 hours (but starts to get a bit muddy after 36). I just aim for 12 but don’t worry if it goes over. You can also brew in the fridge. I didn’t notice much difference between the fridge and the bench. The lower temperature of the fridge might give you an even smoother cup (perhaps too smooth). ↩