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Last week we talked about cold brew and learned that despite the trend of the last decade it’s an old beverage dating back to the 1600s. Concurrent with the widespread cold brew market growth there has also been a rising interest in iced coffee within the coffee industry that’s beginning to expand. 

In part two of our cold coffee series we’re looking at flash chilled iced coffee. Tune into the livestream on Wednesday at 10:30 to brew along with Brian! 

In part two of our cold coffee series we’re looking at flash chilled iced coffee. Tune into the livestream on Wednesday at 10:30 to brew along with Brian! 

I should clarify. Iced coffee can be as simple as pouring left over coffee from the morning over ice. This was common practice in cafes for years before cold brew became popular. Often hot brewed coffee was chilled in the fridge and poured over iced when ordered. It was both bitter and intense, and often flat and stale. Excellent for the caffeine hungry or doctoring into a coffee ice cream of sorts but failed to highlight the defining characteristics of interesting coffees as we aim to do with so many other brewing methods. 

Flash chilled iced coffee is the method of brewing hot coffee that is immediately chilled over ice while brewing. It allows us to get the benefits of using heat in the extraction process while the rapid cooling from the ice chills the coffee and dilutes to our desired strength. The result is that it retains more complexity in the cup than your typical cup of cold brew, and it takes just a few minutes instead of 12-24 hours. While cold brew is quite simple iced coffee requires a little more coffee math, so let’s get into it. 

Ratio and Grind 

As always, we start with our ratio. In this case we’re going to use our typical ratio for hot brewed coffee, 1:16. We’re going to using 50% of the brew water as ice that chills and dilutes the coffee. Choose your desired output and divide by two, this is the amount of ice we will be using while the remainder is going to be the brew water. 

We’re also going to grind slightly finer than we normally would for a Chemex. There will be less water flowing through the bed of coffee so we need a smaller particle size that will give up flavor faster in water, while also slowing down the brew rate so that there is enough contact time to fully extract the desired coffee flavors (read more about the role of grind size and brew rate here). 

The example below is using a 1:16 ratio with 50g of coffee, and with 400g ice and 400g water. 


  • Chemex 
  • Chemex filters 
  • Scale 
  • Kettle 
  • Ice 


  1. Rinse your Chemex filter with cold water. 
  1. Set aside the filter for a moment and add 400g of ice (about 1 and 2/3 cups if starting with water before freezing). Replace the rinsed filter. 
  1. Add 50g ground coffee. 
  1. Bloom the ground coffee with ~100g of water just off boil (typical bloom is generally twice the coffee’s weight in water). Wait 45 seconds to a minute. 
  1. Pour in pulses of ~150g of water until a total of 400g (about 1 and 2/3 cups) has been added. We’re aiming for a brew time of about 3 minutes. 
  1. Once the water has completed the draw through remove the filter and swirl to dissolve any remaining ice. Serve immediately over additional ice if desired. Enjoy! 


As with all brew methods there is lots of room to play around here. Frist, the amount of ice is flexible and can anywhere from 30-50% of the total brew. Not all ice is created equal as different freezers are capable of achieving different temperatures. The colder your ice the more effectively it will chill your coffee and the less you will need. 

How do you know you used the right amount of ice? If the ice has almost completely melted and chilled the coffee by the time the brewing is finished then you’re in a good place. If there are still big cubes swirling around yet the coffee is sufficiently cooled then feel free to use less ice next time. Just be sure to adjust the amount of brew water used accordingly 

If you’re interested in changing the brew ratio we recommend upping the dose to 1:15 or 1:15.5. This is for a couple reasons: if you plan on serving your coffee over ice it will dilute further as you drink it. Starting at a higher strength means that additional melting ice will not make the coffee too watery. Also, cold temperatures mute intensity on our palates and using a tighter ratio can make up for some of that intensity. 

Have a question or a topic you’d like to see covered? Shoot us an email at [email protected], or tune in to the livestream Wednesdays at 10:30am, Brian will be taking questions in the chat! 

Scott Klepper
Scott’s first cafe job served Portland Coffee Roasters. He’s still in coffee eight years later because of the people and community. The free coffee helps.