Pencil hardness

Plot the Points and Draw the Lines and Curves. Using a sharp, hard pencil, plot the experimental points as small dots, as accurately as possible. Draw small circles (or squares, triangles, etc.) of uniform size (2 or 3 mm) around the points in ink to give... 

Reference books list the Mohs hardness for many known minerals and a simple scratch test with a hardness pencil can be used with any unknown materials (providing there is a large enough surface available for scratching). It is conceivable to reverse the situation in that the scratching is done with a particle (or particles) of the material under test, on a surface made of the reference material but no standard procedure is known to the author. 

The substance mixture to be separated and, if necessary, a reference substance, is applied with a micropipette as a spot or band to the start line on the plate which has been sprayed with buffer the start line is at right angles to the applied electric field and is chosen according to the expected direction of migration of the substances. The start points can be marked with a metal or hard pencil. Neighbouring points should be 2—3 cm from each other and the diameter of the spots less than 1 cm. 

A commonly used quick characterization of relative hardness is provided by the pencil scratch test [25] in which a series of standardized, sharp pencils are drawn across the coating at a specific angle to find the softest one that causes a scratch. Thus, coating hardness is reported as that of the scratching pencil (e.g. 4B-4H). The test is obviously subject to a certain amount of subjectivity, since it depends on the force applied to the pencil, the pencil consistency (i.e. different manufacturers of pencils make pencils of slightly different hardness), pencil sharpness and inclination. For this reason, pencil hardness should only be used as a comparative measure of coating hardness, when the same person performs the test on a variety of coatings with the same pencils. 

Hardness Pencil hardness (D3363-74) and Rocker Sward hardness (ASTM D2134-66)... 

Figure 2.22 Photo of a hardness pencil holder that holds the pencil at a precise angle.

E-coat Hardness (pencil) ASTM D3363 Hardness... 

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