5.1 Pencil hardness measurements have been used by the coatings industry for many years to determine the hardness of clear and pigmented organic coating films. This test method has also been used to determine the cure of these coatings, especially when using forced dried heat.

5.2 This test method is convenient in developmental work and in production control testing in a single laboratory. It should be recognized that the results obtained may vary between different laboratories when different manufacturer’s pencils as well as when different substrates are used. To improve test result reproducibility for a specific group of tests, it is recommended to utilize drawing leads or pencils made by the same manufacturer and from the same batch. If drawing leads or pencils from the same manufacturer and from the same batch are not available at the time of subsequent evaluations, it shall be noted on the test report.

Note 3: Using leads or pencils made by different manufacturers or from the same manufacturer but different production batches, may result in significant variation for leads within the same pencil hardness scale.

5.3 This test method has been found to be useful in providing relative rankings for a series of coatings that exhibit significant differences in film hardness. Caution should be used when attempting to compare coatings of similar film hardness.

5.4 This test method may not be appropriate for coatings applied to a wood or other softer substrate in which results may be more a function of substrate deformation than coating hardness.

5.5 If this test method is used as a basis for purchase agreement, maximum precision will be achieved if a given set of referee pencils be agreed upon between the interested parties.

1.1 This test method covers a procedure for rapid, inexpensive determination of the film hardness of an organic coating on a metal or similarly hard substrate in terms of drawing leads or pencil leads of known hardness.

1.2 This test method is similar in content (but not technically equivalent) to ISO 15184.

Note 1: Other procedures are available to measure permanent deformation of organic coatings under the action of a single point (stylus tip) including but not limited to Test Methods D2197, D5178, and G171.

1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.