Hardness

The definition of hardness has, in the past, caused misunderstandings within the paint industry. Most coatings are viscoelastic, and hence will indent to some extent. Therefore,
DIN 55 945 defines hardness as follows:

Hardness is the resistance of a coating to a mechanical force, such as pressure, rubbing or scratching.

In practice, different testing methods are used:

Pendulum Hardness

– In accordance with methods described by König and Persoz

Indentation Hardness

– Shore Durometers
– Barcol Impressors
– Buchholz Indentation Testers

Scratch Hardness

– Hardness Meter Dur-O-Test
– Pencil Hardness

For clear communication of test results, the technician needs to document the type of test method used, for example, “Indentation Resistance in accordance with ISO 2815“ or “Damping Time in accordance with ISO 1522“.

BYK-Gardner offers instrumentation needed to perform various hardness tests.