293 Pencil Hardness Tester
- Brand
- ERICHSEN
- Model
- 293
- Origin
- Germany
- Industries
- Paints, coatings
Features
Pencils of graded hardness are moved over the paint film at a fixed angle and load to determine coating hardness.
The Model 293 Pencil Hardness Tester consists of the instrument body, a set of standard pencils, a special pencil sharpener and a sheet of abrasive paper. Pencils of different hardness grades are moved over the paint film at 45° to the horizontal with a force of about 7.5 ± 0.1 N (the instrument also has 5 N and 10 N settings). When the softer pencil leaves a writing mark and the next harder grade leaves a clear scratch in the coating, these two pencil grades give the pencil hardness – for example 2H…3H means the 2H pencil writes on the surface and the 3H pencil slightly scratches the coating.
The Model 293 is technically in line with the Wolff-Wilborn method, keeping force and angle constant throughout the test. It is simple to operate and removes the influence of the operator on pencil pressure.
The Model 293 Pencil Hardness Tester consists of the instrument body, a set of standard pencils, a special pencil sharpener and a sheet of abrasive paper. Pencils of different hardness grades are moved over the paint film at 45° to the horizontal with a force of about 7.5 ± 0.1 N (the instrument also has 5 N and 10 N settings). When the softer pencil leaves a writing mark and the next harder grade leaves a clear scratch in the coating, these two pencil grades give the pencil hardness – for example 2H…3H means the 2H pencil writes on the surface and the 3H pencil slightly scratches the coating.
The Model 293 is technically in line with the Wolff-Wilborn method, keeping force and angle constant throughout the test. It is simple to operate and removes the influence of the operator on pencil pressure.
Test procedure
1. Preparing the pencil: ① sharpen the pencil so that about 5 mm of lead protrudes; ② hold the pencil vertically with the lead on the abrasive paper (400 grit) and grind the lead flat with a sharp edge.
2. Fitting the pencil: ① turn the instrument's levelling post downwards so that it and the two wheels are level; ② pull the handle outwards, insert the pencil, select the required force setting and let the tip touch the bottom. Release the handle and the pencil is held in place.
3. Testing: place the instrument on the test panel, lift it slightly and turn the levelling post upwards, so that the pencil tip and the two wheels are level. Lower the instrument gently, taking care not to damage the tip. Holding the axle between thumb and forefinger, push the instrument across the panel at about 10 cm/s.
When the softer pencil leaves a writing mark and the harder one just scratches the coating, these two pencil grades give the pencil hardness.
