Wicking

The wicking test focuses on the wire insulation's propensity for drawing fluids into the wire. This can be a concern particularly for applications in which a wire/cable may be regularly exposed to fluids (e.g. wheel well of an aircraft). This test is not common on most wire types, but is found within the MIL-W-81044 (Polyalkene insulated wire) and Spec 55 (XL-ETFE) style wire insulations and should be considered for new insulating material types to identify problems prior to implementation in any application.

In particular, the wicking test measures how far a dye travels up a vertically mounted wire between the jacket and primary insulation. The pass/fail criteria is specification dependent and is typically less than 0.5inches.