A Visible Problem
As Scotch whisky exports expanded during the 1960s and 1970s, a quality issue emerged. Whisky that appeared clear in Scotland would become cloudy when shipped to distant markets or when consumers added ice. This "chill haze" presented challenges for the industry as international sales increased.
Filtration Approaches
The whisky industry faced competing requirements. Some companies applied extensive filtration to ensure their whisky remained clear under all conditions, but this resulted in spirit that had reduced flavour and character. Others used minimal filtration to preserve taste, but their whisky would cloud during long-distance shipping or refrigeration.
Identifying the Cause
Using gas chromatography equipment, Jim Swan identified the specific compounds responsible for chill haze. This allowed the industry to understand the chemical basis of the problem, though identification alone did not provide the complete solution.
Scientists and blenders conducted experiments testing different filtration temperatures, filter types, and processing times. Laboratory notebooks from 1972 document systematic evaluations where each whisky was assessed for both clarity and the effects of filtration on aroma and flavour.
Rather than developing a single method for all whiskies, the work produced guidelines that allowed distilleries to predict whether their spirit would be prone to chill haze. This enabled them to apply appropriate levels of filtration based on the characteristics of individual whiskies.
Industry Impact
This systematic approach addressed the commercial problem while contributing to understanding of how fermentation, distillation, and filtration affected whisky quality. The ability to balance clarity requirements with character preservation became an established component of whisky production.