it is often observed in liquid filtration that a used filter medium performs differently to a new one. After a certain time in operation, any filter medium＇s performance declines, and sooner or later the filter medium has to be rinsed off, washed, and eventually replaced. There are many possible causes for this behaviour, a major one being mechanical blockage of the filter pores by trapped particles. This occurrence is commonly referred to as ＇blinding＇, and is an undesirable side-effect of cake filtration. The paper will discuss its effects.