What are the primary characteristics of a Penetrant?

The material must be absorptive, to perform blotting action

It must have a fine texture but not be too fine, as this may block imperfections

For colour contrast penetrants it must mask out background contours and colours

It must be easily and evenly applicable

It must form a light and even coat

There must be no fluorescing of the developer when used with fluorescent penetrant

The penetrant bleeding from a discontinuity must easily wet the material

When used with a colour contrast penetrant it must be of a highly contrasting colour. It seems agreed that the best colour is white

It must be readily removable after the test is completed

It must be non-toxic and non-irritant