During lautering, a filtration process in beer production, an inhomogeneous filter cake composed of different horizontal layers is formed. Fine particles settle slower than coarse particles and form a layer on top of the cake. Due to its low permeability, the fine layer acts as a stamp on the compressible bottom layer, thus resulting in cake compression and reduced flow rate (stamp effect). A method to prove the stamp effect and investigate its impact on the filtration was developed. The structure of the cake was preserved by freezing, which enabled sampling from different layers at different filtration times. An optical porosity determination (surface roughness) was established to study the compression. A predominant impact of the stamp effect compared with a less pronounced skin effect was shown. To avoid the stamp effect during filtration, a filtration technique was developed, which includes the removal of fines from the filter cake. •Fine particles form a layer on top of the cake during filtration in the lauter tun.•Optical measurement of the cake porosity via the surface roughness was established.•The top layer acts as a stamp (stamp effect) and compresses the bottom layer.•A filtration technique to remove the fine particles before filtration was developed.