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Pencil Hardness Tester

Pencil Hardness Tester

The purpose of scratch hard­ness tests is to determine the resistance of coating materials or lacquers to scratch effects on the surface.
Generally, scratch hardness is measured by moving a sharp object under a known pressure over the test surface.

Here is informative video on how to properly set up and use a pencil hardness tester, or scratch tester.

Part 1



Part 2




Pencil Hardness Test
(By Kevin Biller)

The pencil hardness test is the most common but also the most inconsistent technique to measure the hardness of a coating. Depending upon your needs and your budget, you have a few options to consider. The easiest solution is to purchase a Wolf-Wilburn testing sled from an instrument company such as Byk-Gardner.

This device eliminates most of the operator error inherent to the free-hand method most commonly used. Regardless, pencils have a fundamental variability in hardness due to lot to lot inconsistency and differences in manufacturers of the pencil.

If you would like a more sophisticated and reproducible hardness test for a coated surface you may want to consider the Sward Rocker hardness tester or the Konig Pendulum hardness tester. The Sward Rocker method employs a technique that relies on the physics that a softer surface affects the amplitude of oscillation of a rocking body. Basically the softer surface dampens a rocking disk more quickly than a harder surface does. Be advised that minor differences in coating thickness can affect your data. ASTM D2134 covers this technique in detail and you can purchase this instrument from Paul N Gardner at:
http://www.gardco.com/pages/hardness/703swardhardness.cfm

The Konig Pendulum hardness method works on a similar principle. With this technique the hardness of a coated surface is measured by tracking the dampening effect it has on an oscillating pendulum. This method consists of placing two stainless steel balls on the coated surface. The balls act as the pivot point at the top of a pendulum. The pendulum is swung from a fixed start position and the number of swings is counted. More elastic or softer surfaces will dampen more quickly and thus swing fewer times. This technique is described in detail is ASTM D4366. You can find this device on Qualitest's website:
http://www.worldoftest.com/pendulumhardness.htm


Kevin Biller
The Powder Coating Research Group
15 W. Cherry Street
Columbus, OH 43215
614-354-1198
www.powdercoatingresearch.com