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CO₂ is introduced into the beer so that a specific volume of foam is produced. The mean retention time of the bubbles in the foam serves as a measure for the foam stability, which is calculated as the relationship between the time required for the foam to collapse and the logarithm of the relationship between the volume of the collapsed foam and the foam still present [1–3].

This method is frequently applied in instances when the influence of carbon dioxide content on foam formation in the beer is to be eliminated.

In determining the foam stability with the Steinfurth Foamtester SFT, the time required for the foam to collapse in a graduated cylinder is measured.

The pressurization is carried out in such a way that the container does not require degassing. The attempered beer is injected into the measuring cylinder through a nozzle, and in the process, foam is formed. The foam stability is determined by several optical sensors detecting the time necessary for the beer/foam interface to pass by them. The precise metering of a predetermined quantity of beer, the entire process of executing the analysis and displaying the results as well as cleaning and conditioning of the measurement cylinder are performed automatically.

The measurement with the NIBEM Cling Meter (fig. 1) is normally performed immediately after the NIBEM foam stability measurement and serves to provide additional information on foam quality. 

After the preset timer has expired, a scan head is introduced into the Haffmans standard glass while the glass is rotated slowly at a fixed level, in order to ensure that the foam has collapsed a minimum of 48 mm. An LED on the back of the scan head emits light. The diffused light, which reflects off of the inside of the glass, is read by a sensor and recorded.