Cold Brew Coffee Ratios, Time, and Grind Size: How to Determine Parameters and Recommended Coffee Beans

In the depths of summer, it's almost a disservice to coffee lovers not to keep cold brew in the refrigerator. But with so many beans on the market, which ones suit cold brew? And how should it be stored—how long does it actually keep? FrontStreet Coffee answers these questions one by one.

Cold brew coffee, as the name suggests, extracts coffee in cold water. Because the water temperature is low, the resulting coffee lacks the bitterness of hot extraction, leaning instead toward sweet and sour notes with a more pronounced fermented character. And precisely because the water is cold, extraction takes far longer than with hot water.

Cold brewing has a long history. Japan is said to have been drinking cold-brewed tea as early as the 17th century, and the Dutch—then the great seafaring nation—adapted the technique to coffee, avoiding dangerous open flames on long voyages and solving the problem of getting hot water at sea.

Today, many specialty shops, FrontStreet Coffee included, keep dedicated cold coffee equipment on hand. Cold brew's smooth, sweet character is exactly what a hot afternoon calls for, which is why it has drawn so much attention.

At FrontStreet Coffee, "cold coffee" actually covers two methods: ice drip and cold brew. Both are served at FrontStreet Coffee outlets to suit different tastes.

Right next to the espresso machine sits the ice drip tower. It consists of a water reservoir, a regulating valve, a coffee chamber, a serpentine tube, and a carafe for the finished coffee.

For ice drip, FrontStreet Coffee typically picks beans with bright acidity, such as its Guji lot.

FrontStreet Coffee Ice-Drip Recipe

Coffee: 60 grams
Coffee-to-Water Ratio: 1:10
Water Temperature: 0–4°C
Grind Size: 80% pass-through on a #20 standard sieve
Extraction Time: 6–8 hours

1. Set a round filter paper in the coffee chamber and moisten it.
2. Press the paper's edge firmly against the chamber wall, add the ground coffee, and level the bed.
3. Place a second round of filter paper on top of the coffee bed.
4. Start a slow pre-infusion with a small amount of ice water, poured from the center of the top paper.
5. Fill the reservoir with an ice-water mixture and set the drip valve to roughly 7 drops per 10 seconds.
6. When the drip finishes, seal the coffee in a glass bottle and refrigerate it overnight so the flavors meld into a thicker, smoother texture.

Why the 1:10 ratio? Because tastes differ—some want richness, others refreshment. At 1:10 the coffee starts concentrated, and FrontStreet Coffee typically serves it over one or two ice cubes. As the ice melts, the strength falls to a level that suits lighter palates, so one ratio accommodates both.

The second filter paper on top of the bed serves a purpose too: without it, dripping water would carve craters into the grounds and cause uneven extraction.

Of course, without a proper ice drip tower at home, most people can't make ice drip. But iced coffee is still easy—cold brew is the go-to.

FrontStreet Coffee Cold Brew Recipe

1. Pour the ground coffee into a sealable glass bottle.
2. Add room-temperature or ice water at a 1:10 coffee-to-water ratio, making sure all the grounds are thoroughly wetted.
3. Seal the bottle and refrigerate for 8 to 12 hours.
4. Once extraction is complete, filter the coffee into a clean sealed bottle and store it in the refrigerator.

Customers at FrontStreet Coffee often ask: which has more caffeine, cold brew or an iced Americano? The common assumption is that cold extraction, being gentle, must pull less caffeine. In fact the opposite is true. Because water stays in contact with the grounds for many hours, extraction runs long—and over that time, caffeine release adds up. Cold brew actually contains more caffeine than an iced Americano.

When choosing beans for ice drip, FrontStreet Coffee favors lighter roasts with fuller acidity, since fruity sweet-sour notes are most pleasant at low temperatures. Distinctive process beans work wonderfully too—Sherry beans, aged in whisky barrels, produce an ice drip with rich fermented wine aromas and real character.

For a brighter, more refreshing cup, FrontStreet Coffee recommends the Guji beans. The result tastes like chilled mixed berry juice—flavors of berry and passion fruit, a gentle fermented aroma, and an addictive sweet-tart finish.

These remarkable beans come from the Buku Abel washing station in the Guji growing region. Guji coffees are usually natural-processed, which is where their lush berry character comes from.

In 2017, DW company entered this Guji lot in that year's TOH competition and won first place in the Ethiopia natural category. Beijing green coffee merchants then brought it to mainland China, and thanks to its lingering strawberry-and-cream flavor it was named "Hua Kui"—literally "flower champion," the best among flowers. That same year, at the China Brewers Cup, competitor Li Jianfei used this coffee to beat a field that included many Gesha entries, taking an impressive second place—and Hua Kui's fame was sealed.

The ice drip FrontStreet Coffee makes with these beans opens with layered berry-juice notes and a long, creamy aftertaste. As the ice melts and the strength eases, the fermented character softens, but the sweet-tart berry core stays outstanding to the last sip.

FrontStreet Coffee Recommendation

Both of these coffees are ideal for home cold brew, too. The Hua Kui lot, with its natural-process sweetness, yields notes of magnolia, creamy strawberry, dried mango, guava, and black tea when cold-brewed—the florals intensify while roasty bitterness all but disappears.

For maximum juice, go with FrontStreet Coffee's Kenya "Cherry Tomato": SL28 and SL34 from Thika, K72 double-washed and light-medium roasted. Cold extraction lays out cherry tomato, snow pear, dark plum, and prune in full—low bitterness, vivid acidity, and a long, fragrant finish over ice.