1. n. [Drilling Fluids]

A type of static filtration test for water-based drilling fluid that measures the filtration rate (time for free water to pass between two electrodes) using filter paper as the medium. It is used primarily to indicate filtercake permeability, but data from the test have been used to study how clays and shales react in filtercakes and how brines of various types affect clays in a filtercake.

Alternate Form: capillary suction time test