After longer periods of storage, filtered beer loses its clarity and brilliance, especially when it is cooled, to the point that haze or a sediment layer forms in the beer. In order to eliminate sensitivity to cold and to avoid undesirable haze or turbidity, beer is often treated with clarifying agents, which allow beer to remain free of haze for months longer than it would without such treatment. Because it is valuable to gain some insight into the stability of packaged beer as early as possible, methods of analysis have been developed that provide information immediately after the packaging process regarding the propensity of a beer to form haze.
A defined amount of formaldehyde is added to beer. Haze forms in the beer which is correlated with "warm days".
Valid for all non-turbid beers
The formation of haze is forced through the addition of formaldehyde and storage at 0 °C. The difference in the turbidity formed and the turbidity at the beginning is compared.