🧊 Steeped Right: The Complete Guide to Cold Brew Coffee

🧊 Steeped Right: The Complete Guide to Cold Brew Coffee

by REL Coffee | The Chemist’s Journal

Cold brew is often labeled as “easy”—just grind, soak, and wait. But if you've ever tasted cold brew that’s flat, bitter, or overly sour, you know there’s more to it.

At REL, we approach cold brew like a slow extraction experiment. It’s not about speed—it’s about control. Every variable matters: the grind size, ratio, steep time, water temp, and roast profile. In this guide, we’ll walk through each of those and how to tweak them for a better, more balanced cup.

Whether you’re brewing a batch at home or dialing it in for your shop, this will help you get it right.

1. Why Cold Brew?

Cold brew isn’t just iced coffee. It’s brewed cold from the start—usually over 12–24 hours—which creates a smoother, low-acid, high-body drink.

Done well, it’s chocolatey, sweet, and clean. Done poorly, it’s hollow or harsh.

2. Coffee Origin — Base Notes First

Cold brew flattens brightness and elevates body, so some origins work better than others.

Best Choices:

• Brazil – Nutty, chocolate, great base.
• Colombia – Balanced, versatile, adds structure.
• Guatemala – Cocoa, mild acidity, depth.
• Sumatra – Earthy and syrupy (best in blends).
• Ethiopia – Bright and floral, but may get lost unless used carefully or in a blend.

Tip:

• Use washed or honey-processed coffees for clarity.
• Naturals can add funk or overripe fruit—best in small percentages.

3. Roast Profile — Roast Drives Flavor

Cold brew needs more solubility to extract well at lower temps.

Best Range:

• Medium to medium-dark roast
  • Caramel, nutty, cocoa notes shine here.
  • Avoid roasts that are too light—these struggle to extract fully and often taste grassy or sharp.

Roast Tweaks:

• If your cold brew is sour or green → roast slightly longer, or increase development time.
• If it's bitter or flat → roast a touch lighter or reduce drop temp.

4. Grind Size — Surface Area + Contact Time

Grind size controls how quickly flavors extract. For cold brew, you’re steeping for hours—so coarse is best.

Starting Point:

• Grind size: Similar to French press or slightly coarser
  (On a Bunn G3: “Coarse”)
• Too fine = over-extraction → bitterness
• Too coarse = under-extraction → weak or sour

Tip:

• If your cold brew is sharp or astringent, go coarser.
• If it’s watery or hollow, go slightly finer.

5. Ratio — Use a Proven Recipe

We recommend starting with the Toddy standard cold brew recipe:

340g of coffee
1.9L of water
Steep for 12–24 hours, depending on temperature.

This yields a concentrate that’s meant to be diluted 1:1 before serving. It’s strong, sweet, and designed to hold up to ice or milk without tasting watered down.

Adjustments:

• Prefer ready-to-drink strength straight from the brew?
  Try a 1:12–1:14 ratio instead (e.g. 85g coffee to 1L water).
• Want more intensity? Brew with the full recipe but dilute less (e.g. 2:1 or to taste).

6. Brew Time — Patience + Extraction

Cold brew happens slowly. Brew too short and it tastes sour or thin. Brew too long and bitterness can creep in.

Ideal Range (for Toddy or similar systems):

• 12–16 hours at room temperature
• 18–24 hours in the fridge

Keep your variables consistent: same water temp, same brew time, same coffee. That’s how you get repeatable results.

7. Water Temperature — Cold is a Spectrum

Even within “cold brew,” temp affects flavor.

• Room temp (65–75°F): Faster extraction, more roundness.
• Fridge temp (34–40°F): Slower extraction, smoother finish.

Tip:

• Brewing in the fridge? Steep longer.
• Brewing at room temp? Stay under 16 hours for balance.

8. Filtration — Clarity and Clean Cup

After steeping, filter thoroughly to avoid sludge and over-extraction.

Best Methods:

• Toddy-style filters: Built-in paper filter with mesh bottom
• DIY approach: Fine mesh → paper or cloth filter pass
• For extra clarity: pass through a Chemex or V60 filter after initial drain

Cloudy cold brew is often a sign of under-filtering or agitation during draining.

9. Troubleshooting — Common Cold Brew Issues

Conclusion: Cold Brew You Can Count On

Cold brew is patient coffee. It rewards planning, precision, and a few dialed-in variables. You don’t need to guess—you just need a system.

Start here:

• 340g coffee → 1.9L water
• Grind: coarse
• Time: 12–16 hours at room temp
• Dilute 1:1 before serving
• Store cold. Drink within 7–10 days.

Then tweak one thing at a time.

That’s how we do it at REL Coffee.
Not just cold coffee—cold coffee with control.

📌 Summary: Cold Brew Cheatsheet