Filter cake washing is a purification method for particulate products in liquids. This process is mostly one step of a sequence in a solid-liquid separation process. For soluble products not only the mechanical transport mechanisms in washing but also the dissolution process of the product must be considered in order to describe the washing process appropriately. An unconsidered dissolution may cause problems and often severe product loss depending on the material properties. This paper presents several methods of soluble solids washing including filter cake washing by pressure and centrifugal forces as well as moving bed washing. The advantages and drawbacks of each method are discussed to evaluate the suitability of its technical application. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.