Alkalinity in Water

What is alkalinity in water? In the context of coffee, alkalinity is a measure of the water's ability to neutralize acids. While total hardness measures calcium and magnesium, alkalinity specifically tracks the presence of bicarbonate and carbonate ions. These ions act as a chemical buffer, preventing the pH of your brew from dropping too rapidly during extraction.

When you brew coffee, the water interacts with the organic acids present in the roasted beans. If your water has very low alkalinity, these acids can dominate the cup, leading to a sharp, sour, or thin-tasting experience. Conversely, if the alkalinity is too high, it will neutralize too much of the coffee's acidity, resulting in a flat, dull, or chalky cup that lacks the vibrant character the roaster intended.

For specialty coffee, the Specialty Coffee Association (SCA) recommends an alkalinity level of approximately 40 mg/L (as CaCO3). This range is generally considered the "sweet spot" for balancing the bright, fruity notes of high-quality beans with the necessary body and mouthfeel. It allows the coffee's natural acidity to shine without becoming aggressive or unpleasant.

In practice, managing alkalinity is one of the most effective ways to improve your home brewing. If you find your coffee consistently tastes sour regardless of your grind size, your water may be too soft or low in alkalinity. If it tastes muted or "muddy," your water might be too alkaline. Many enthusiasts use mineral-added water packets or reverse osmosis systems to dial in these specific numbers, ensuring that the water chemistry supports, rather than hinders, the flavor profile of the coffee.