A malt sample (50 g) is mechanically separated into its hard and crumbly constituents. The grains are pressed against a rotating sieve drum for 8 minutes by a roller with constant spring pressure. The crumbly parts fall through the wire braiding. Glassy grains and hard broken parts remain in the sieve drum. As far as the hard malt components are concerned, a distinction is made between partial hyaline and whole hyaline. The individual fractions are weighed and converted to a percentage. The percentage values are a constituent of the malt specification between breweries and malthouses.
Excessive glassiness has a detrimental effect during the mashing and lautering process. Deficiencies occur in the brewing process in wort clarification, fermentation, maturing and filtration, whereby climate and variety-related influences can occur.