Hoffman Scratch Hardness Tester

To operate, attach riders to the scale arm at the numbered positions. The carriage is held down firmly by hand and moved in the opposite direction, to cause a trailing scratch. The large standard rider loads 100 g per division, while the small rider loads 25 g per division. This small rider may be used for making low-range measurements involving small increments of pressure, or it may serve as a vernier with the large rider in making more precise medium-range measurements.

Scratch Hardness
The force necessary to cut through the film to the substrate.

Adhesion
The force required to scrape a path through the film, when the stylus begins its motion on an uncoated portion of the panel.