The test pens contain, similar to the test inks, fluids of defined surface tension. The surface energy of the material to be checked is determined simply by applying a stroke of ink with the tip of the felt pen. The accuracy of the measurement is, like the one of the test inks, 1mN/m.

The test pens are available in a set of 8 pens from 30 to 44 mN/m.

On special demand also bigger or smaller values are available.