A Hegman gauge is used by puddling a sample of paint at the deep end of the gauge and drawing the paint down with a flat edge along the grooves. The paint fills the grooves, and the location where a regular,significant "pepperiness" in the appearance of the coating appears,marks the coarsest-ground dispersed particles. The reading is taken from the scale marked next to the grooves, in dimensionless "Hegman units"and/or or micrometers
Determining the fineness of paint's grind is important, because too coarse a grind may reduce the paint's color uniformity, gloss, and opacity. The Hegman gauge is widely used for this purpose because it requires minimal skill and only a few seconds' work.
Hegman gauges are commonly available in the following ranges: 0 to 100 micrometres, 0 to 50 micrometres, 0to 25 micrometres,
0 to 15 micrometers and 0 to 10micrometres