Tag: quality-control

Every municipal supply is required to carry residual chlorine. Chlorine reacts with phenols to make chlorophenols, and microbes turn chlorophenols into chloroanisoles — taint compounds that whisky panellists detect at a few nanograms per litre, below the limit of detection of routine GC-MS. This is why free chlorine in blending water is written as a hard zero rather than a number.

A 2025 study found PFAS in 95% of the American beers it tested, and traced them to the municipal water the breweries used rather than to anything in the brewing. Spirits are reduced to bottling strength with water too — often a third of the finished bottle by volume — and 2026 is the year the rules on that water started to bite on both sides of the Atlantic.

Every bottle of whisky below cask strength is the result of one of two engineering choices. Either the spirit and the water met in a vat, were rested, gauged and corrected — or they met in a pipe, metered against each other in real time, with no second chance. The finished liquid can be identical. What the two routes demand of the water is not.

Drinking-water science says demineralised water is a bad idea — flat-tasting, mineral-poor, and corrosive to pipework. Regulators agree, and several set a minimum mineral content for treated drinking water. So why does every serious proofing specification run in the opposite direction, toward zero? Because the water in a whisky bottle is not the water in a glass, and the arithmetic that governs one has almost nothing to do with the other.

A blending-water specification is a list of limits. A certificate of analysis is a list of claims that those limits were met. Between the two sits a set of standardised analytical methods — conductivity by a three-stage pharmacopoeial test, organic carbon by oxidation, trace ions by ICP-MS and ion chromatography, organisms by culture, and taste by a trained panel — each with its own blind spots. Here is what actually measures what, why two honest certificates can disagree, and the questions that separate an audited supplier from a confident one.

A water softener takes hardness to zero, and a lot of people read that as "the minerals are gone." They are not. Ion exchange swaps calcium and magnesium for sodium and leaves total dissolved solids, alkalinity, chloride, sulphate and silica exactly where it found them — while adding sodium and a chlorine demand of its own. Here is what a softener actually does to water, why that is the wrong answer for spirit reduction, and the one place it genuinely earns its keep in a blending-water plant.