Compared to other organic and inorganic crystals, protein crystals are much more sensitive to any kind of mechanical stress. The present work focuses on the influence of compressive stresses during cake Filtration on lysozyme crystals. Crystals of two different morphologies, isometric and needle-shaped, are considered. Breakage of both crystal types is observed. However, not only the extent, but also the type of breakage mechanism differs for the two types of crystals. Isometric crystals only exhibit breakage of edges away from the whole crystals, whereas needles are broken totally. Compressibility and general cake resistance of needle-shaped crystals are higher than those of isometric crystals. It can be concluded that the breakage of crystals contributes to the general compressibility and resistance of filter cakes, but the influence of absolute size and morphology is much higher. (c) 2014 Elsevier Ltd. All rights reserved.