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How do you split water and ice for flash-brew iced coffee?
Published by Ratio Kettle
Count both the hot brew water and the carafe ice in your total water budget. For a 24-gram dose with 384 grams total at 1:16, one starting split is 256 grams of hot water through the grounds and 128 grams of ice in the carafe.
Give the two ratios different names
Only the hot water passes through the bed and extracts coffee. Both the hot water and any melted ice affect the drink. In the example, the hot-water ratio is 256 ÷ 24, roughly 10.7 parts water per part coffee. The planned total including the ice is 384 ÷ 24, or 16 parts.
A recipe labeled 1:11 can therefore describe a very different drink depending on whether the author counts ice. Counter Culture lists its hot water and ice separately. Read both lines before using a ratio from another recipe.
Set up the scale in two steps
Rinse the filter and discard that water before putting ice in the serving carafe. Weigh 128 grams of ice in a heat-safe carafe large enough for the batch. Fit the dripper with the grounds, then tare the whole assembly. Now your last pour should stop at 256 grams on the scale, including any bloom water.
As the brew finishes, swirl the carafe to mix the hot coffee with the meltwater. Note whether ice remains before comparing the strength with a previous brew. Ice left in the glass keeps diluting as you drink.
Diagnose a watery glass
First check the serving ice. An additional 40 grams of ice melting completely takes this recipe from 384 to 424 grams of total input water, changing the planned 1:16 to about 1:17.7. That difference can be large enough to conceal a change you made at the grinder.
For a closer comparison, pour each trial into a chilled empty glass and taste at the same time after brewing. Record dose, hot water, carafe ice and serving ice separately so you can remake the version you liked.