There are few things more disappointing than a bad coffee to start your day. Whether it’s bitter, watery, or bland, a poor brew can be traced back to two main factors: the grind size and the dose. These need to work together perfectly to deliver the balanced flavour and body you expect from great coffee. If the grind is too fine, water struggles to pass through, resulting in bitterness. Too coarse, and the water runs through too quickly, leaving you with a thin, sour cup.

Grind Size and Texture

The grind size determines how quickly water moves through your coffee and how much flavour it extracts. For espresso, the grind should be fine and even to create the right resistance. For brewing methods like French press or cold brew, coarser grinds are essential to avoid over-extraction and bitterness.

Over-Extraction

A grind that’s too fine packs tightly when tamped, forcing water to move through slowly. This prolonged contact results in dark, bitter flavours and an oily texture.

Under-Extraction

A grind that’s too coarse leaves large gaps for water to flow through too quickly. This short brewing time produces a coffee with a thin body and sharp, acidic flavours.

Finding the Ideal Grind

There’s no single perfect grind for all coffee, it depends on the brewing method. A quality grinder allows you to adjust precisely, or you can buy freshly ground coffee to your preferred size.

Coffee Dose

The dose is the amount of coffee used, which influences the strength and balance of the final cup. Using too much can cause over-extraction; too little can lead to under-extraction.

Over-Extraction

Packing in too much coffee especially with a fine grind creates resistance against the water, slowing extraction and resulting in bitterness.

Under-Extraction

Too little coffee, or a grind that’s too coarse, means water passes through quickly, creating a weak, sour brew.

The Correct Dose

The Specialty Coffee Association (SCA) recommends a ratio of 1:18 - that’s 1 gram of coffee for every 18 grams of water, as a guide. However, you can adjust this to taste and method.

Perfecting Your Home Coffee

The grind size and dose work hand in hand to create balance in every cup. Understanding and adjusting both will help you avoid bad coffee and enjoy consistent results. If you’re grinding at home, invest in a quality grinder to get the size right every time. At Merlo, we can also grind your coffee to the exact size you need when you order online or in-store, helping you brew specialty coffee with the perfect flavour and texture, every time.