The Zestron Flux Test indicates carboxylic-based flux activators through a color reaction. The test is an important supplement to the ionic contamination measurement, as non-visible flux residues can be easily detected. 

Additionally, The Zestron Flux Test helps to visualize the local distribution of contamination with flux residues which in turn ensures an improved component reliability assessment. Residues based on halogenated activators, however, cannot be detected with the Zestron Flux Test Kit.