Hegman gauge

A Hegman gauge, sometimes referred to as a grind gauge or grindometer, is a device used to determine how finely ground the particles of pigment (or other solid) dispersed in a sample of paint (or other liquid) are. The gauge consists of a steel block with a series of very small parallel grooves machined into it. The grooves decrease in depth from one end of the block to the other, according to a scale stamped next to them. A typical Hegman gauge is 170mm by 65mm by 15mm, with a channel of grooves running lengthwise, 12.5mm across and narrowing uniformly in depth from 100 μm to zero. A Hegman gauge, sometimes referred to as a grind gauge or grindometer, is a device used to determine how finely ground the particles of pigment (or other solid) dispersed in a sample of paint (or other liquid) are. The gauge consists of a steel block with a series of very small parallel grooves machined into it. The grooves decrease in depth from one end of the block to the other, according to a scale stamped next to them. A typical Hegman gauge is 170mm by 65mm by 15mm, with a channel of grooves running lengthwise, 12.5mm across and narrowing uniformly in depth from 100 μm to zero. 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 'pepperyness' 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 mils or micrometres. Hegman units are defined in terms of an inverted size scale as shown below: Determining the fineness of a 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.