The focus of this article is on empirical modelling of filter cake washing. The filtration experiments introduced in this paper were conducted by using a pilot-scale (0.1 m(2)) filter press according to the basic principles of factorial designs. Five different variables of the filtration, pressing, cake washing, and air drying stages were considered in the tests and the examined product characteristics were the overall capacity of the filter and the purity of the cake. The results obtained from the tests were used for creating different kinds of regression models for explaining the influence of the studied variables on the success of the cake washing process. The goal of the modelling strategy for the cake washing was to determine the simplest empirical models and compare these with theoretical equations complemented with linear terms. It was found that the empirical equation could model the results more accurately than the theory-based equations could.