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This method is based upon on the fact that the β-glucan-rich cell walls of the endosperm are progressively broken down during malting. This process can be made visible by staining the cell walls that are still intact with the fluorochrome Calcofluor, which exclusively binds β-glucans starting at a molecular weight of approx. 10,000 D. 

Modification is revealed by allowing the barley kernels, which have been cut in half, to react with Calcofluor (with Fast Green as a contrast medium). The kernels are subsequently examined under UV light (365 nm) in a suitable analyzer device. An intense, bright blue fluorescence occurs where unmodified endosperm cells are present, while the modified parts appear dark blue.

The Kolbach index is used to express the quantity of the nitrogenous substances found in malt, which go into solution under the conditions present during the Congress mash method. It is a measure of the degree of proteolytic modification of the malt and also provides an indication for the quantity of proteolytic enzymes contained in the malt. The Kolbach index is less conclusive than other methods due to its dependence on the total nitrogen content and the provenance of the barley. Therefore, it must always be considered together with the total nitrogen content.

Using this method, a steeping process, divided into steeping and air rests, is simulated. A practice-oriented process (with two and four days of germination) is implemented, which has proven useful for shorter, modern germination processes.