I  Cold Brew

Lab file · From the literature

What actually changes between cold brew and a French press?

Short answer

At room temperature, 8 hours matched the French press for strength and caffeine, with higher pH and less titratable acid. The fridge brew came out weaker.

Literature review1 source · Updated 2026-10-04

Key numbers
Strength, room-temp cold brew (23 °C, 8 h)
2.95% TDS[1]
Strength, French press (10 min)
2.95% TDS[1]
Strength, fridge cold brew (4 °C, 20 h)
2.71% TDS[1]
Brew kept by 1 g of spent grounds (approx.)
2g[1]
Illustration of a glass French press with its plunger raised beside a clamp-top glass jar of steeping cold brew, both in cross-section with loose grounds suspended in the coffee, steam above the press and a thin frost line on the jar.

The data

A 2023 study from the University of Guelph took one Colombian medium roast and brewed it every way that matters here: loose grounds in water at fridge, room and warm temperatures, at four ratios, and at five grind sizes. Then it put three brews side by side: cold brew from the fridge, cold brew from the counter, and a French press [1].

Temperature sets the pace

Warmer water extracted faster. After 5 minutes at a strong 1:3 ratio, the 4 °C brew had reached 3.6 % dissolved solids, against 5.8 % at 37 °C. By 18 hours the gap had mostly closed, though the fridge brew still trailed [1].

Warmer water gets there faster; 18 hours narrows the gapTotal dissolved solids after 5 minutes and after 18 hours of loose-grounds immersion at three temperatures, 1:3 ratio
  • 5 min
  • 18 h
2468Total dissolved solids (%)4 °C (fridge)4 °C (fridge), 5 min: 3.6 %3.64 °C (fridge), 18 h: 6.2 %6.223 °C (room)23 °C (room), 5 min: 5.1 %5.123 °C (room), 18 h: 6.8 %6.837 °C (warm)37 °C (warm), 5 min: 5.8 %5.837 °C (warm), 18 h: 7.0 %7.0
2468Total dissolved solids (%)4 °C (fridge)4 °C (fridge), 5 min: 3.6 %3.64 °C (fridge), 18 h: 6.2 %6.223 °C (room)23 °C (room), 5 min: 5.1 %5.123 °C (room), 18 h: 6.8 %6.837 °C (warm)37 °C (warm), 5 min: 5.8 %5.837 °C (warm), 18 h: 7.0 %7.0
Data table

Values in %

5 min18 h
4 °C (fridge)3.66.2
23 °C (room)5.16.8
37 °C (warm)5.87.0

Re-plotted from values reported in section 3.1 of source [1].

The pace is the surprising part. With loose grounds, every temperature passed 90 % of its 18-hour strength within an hour. Bag-steeped studies, like the one behind our steep-time file, took closer to 7 hours. The authors put that down to the bag slowing things. They also note that the compounds behind body (polysaccharides, proteins, melanoidins) probably keep dissolving well after the fast part is done.

Grind did what the textbook says, with loose grounds: after 5 minutes the finest grind (282 µm) was at 93 % of its final strength and the coarsest (1,057 µm) at 61 %. That’s the opposite of the bag result in our grind-size file, and it’s a good reason to treat that one as a bag result.

Cold vs hot, same coffee

For the head-to-head, all three brews were made in a French press at 1:6: 20 hours in the fridge, 8 hours on the counter, and 10 minutes with just-off-boiling water. The counter cold brew and the French press came out at the same strength, 2.95 %. The fridge brew reached 2.71 % even with 20 hours [1].

At matched strength, the cold brews still had a higher pH and less titratable acidity:

pH: both cold brews sit higher than the French pressSame coffee at 1:6. Lower pH is more acidic.
5.15.25.35.4pHFridge, 4 °C, 20 hFridge, 4 °C, 20 h, pH: 5.385.38Room temp, 23 °C, 8 hRoom temp, 23 °C, 8 h, pH: 5.345.34French press, 10 minFrench press, 10 min, pH: 5.185.18
5.15.25.35.4pHFridge, 4 °C, 20 hFridge, 4 °C, 20 h, pH: 5.385.38Room temp, 23 °C, 8 hRoom temp, 23 °C, 8 h, pH: 5.345.34French press, 10 minFrench press, 10 min, pH: 5.185.18
Data table
pH
Fridge, 4 °C, 20 h5.38
Room temp, 23 °C, 8 h5.34
French press, 10 min5.18

Re-plotted from values reported in Table 1 of source [1]. All three differ significantly by the authors' Tukey test.

Titratable acidity: lower in both cold brewsAcid neutralized when titrating to pH 7.0, as grams of acetic acid per liter
0.800.850.900.951.00Titratable acidity (g/L)Fridge, 4 °C, 20 hFridge, 4 °C, 20 h, Titratable acidity: 0.86 g/L0.86Room temp, 23 °C, 8 hRoom temp, 23 °C, 8 h, Titratable acidity: 0.87 g/L0.87French press, 10 minFrench press, 10 min, Titratable acidity: 0.97 g/L0.97
0.800.850.900.951.00Titratable acidity (g/L)Fridge, 4 °C, 20 hFridge, 4 °C, 20 h, Titratable acidity: 0.86 g/L0.86Room temp, 23 °C, 8 hRoom temp, 23 °C, 8 h, Titratable acidity: 0.87 g/L0.87French press, 10 minFrench press, 10 min, Titratable acidity: 0.97 g/L0.97
Data table

Values in g/L

Titratable acidity
Fridge, 4 °C, 20 h0.86
Room temp, 23 °C, 8 h0.87
French press, 10 min0.97

Re-plotted from values reported in Table 1 of source [1]. The two cold brews don't differ significantly from each other; both differ from the French press.

Caffeine and chlorogenic acid in the counter cold brew were statistically the same as in the French press. The fridge brew had less of both, in line with its lower strength. The cold brews were also lighter in color and slightly less viscous [1].

Why your yield is smaller than your water

Spent grounds hold on to brew. From preliminary runs, the authors estimate each gram of grounds keeps about 2 g of liquid. The stronger the ratio, the bigger that loss is as a share of the batch. At 1:3, only 6.8 % of the coffee’s mass ended up in the brew you could pour off, against 16.56 % at 1:11 [1]. That ~2 g figure is the same one our calculator uses for expected yield.

At strong ratios, the grounds keep a big share of the brewActual extraction yield after 18 h at 23 °C, counting only the brew that drains off
05101520Actual extraction yield (%)1:31:3, Actual extraction yield: 6.80 %6.801:61:6, Actual extraction yield: 13.64 %13.641:91:9, Actual extraction yield: 16.10 %16.101:111:11, Actual extraction yield: 16.56 %16.56
05101520Actual extraction yield (%)1:31:3, Actual extraction yield: 6.80 %6.801:61:6, Actual extraction yield: 13.64 %13.641:91:9, Actual extraction yield: 16.10 %16.101:111:11, Actual extraction yield: 16.56 %16.56
Data table

Values in %

Actual extraction yield
1:36.80
1:613.64
1:916.10
1:1116.56

Re-plotted from values reported in section 3.2 of source [1]. The authors estimate about 2 g of brew stays in each gram of spent grounds.

How they measured it

Sixty grams of coffee per batch, from a single roast batch, ground on a burr grinder and sized with a particle size analyzer. For the timing runs, loose grounds were stirred into tap water in sealed glass beakers at 4, 23 or 37 °C, sampled at 5, 10, 30 and 60 minutes and 18 hours, and paper filtered. Strength was read on a coffee refractometer. pH was measured directly, and titratable acidity by titrating to pH 7.0. Caffeine and chlorogenic acid were measured by HPLC. Differences in the cold-vs-hot table were tested with Tukey’s test. There was no tasting panel.

Limits

  • No tasting. "Less acidic" here means pH and titratable acidity. The authors suggest that explains why people find cold brew less acidic, but they didn't test it.
  • The paper never says how many times each brew was repeated, or whether its ± figures are standard deviations or standard errors.
  • The French press is described as 720 g of water on 60 g of coffee, which is 1:12, while the paper calls it 1:6. Matching strength suggests 1:6, but we can't confirm which number is the typo.
  • The French press used the coarsest grind. The paper doesn't say what grind the two cold brews used.
  • The timing experiments sampled at 5, 10, 30 and 60 minutes, then jumped to 18 hours. Nothing in between. So it can't tell 8 hours from 12 from 18.
  • Those timing runs were at 1:3, far stronger than anything you'd drink. The weakest ratio tested was 1:11; ready-to-drink recipes run weaker still.
  • One Colombian medium roast from one batch, in Ontario tap water. Different beans, different water: we don't know.
  • Loose grounds reached most of their final strength within an hour here, much faster than bag-steeped studies. The authors blame the bags. They didn't test bags side by side, so that's a strong guess, not a result.

Takeaway

For cold brew as strong as French press, room temperature gets there: 8 hours at 1:6 matched it. In the fridge, expect a weaker brew at the same ratio, so use more coffee or more time. Either way, expect higher pH and less titratable acid than hot. At 1:6 this is concentrate strength, so dilute to taste.

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Related gear and coffee

Sources

  1. Wang, X. & Lim, L.-T. (2023). Effects of grind size, temperature, and brewing ratio on immersion cold brewed and French press hot brewed coffees. Applied Food Research 3, 100334. doi:10.1016/j.afres.2023.100334Peer-reviewed

Charts are re-plotted from numbers printed in the sources' text and tables, never traced from their figures. How we pick and handle sources: about the Lab.