PH1100 Pencil Hardness Tests

The NK durometer performs the Wolff-Wilborn scratch test, measuring the surface hardness of paints and coatings using pencils of different hardness levels under controlled pressure and angle.

The NK pencil scratch test is a precise technique for measuring the surface hardness of paints, coatings, varnishes and inks. This method, based on the Wolff-Wilborn method, ensures repeatable and reliable results through the use of pencils with different hardness grades under controlled pressure and angle conditions.

This test is widely valued in sectors such as furniture, automotive, synthetic resin development and other coating industries.

How does the Wolff-Wilborn test work?

The principle of the test is simple but effective: pencils of known hardness are moved across the coating surface under a fixed load of 750 g and at a 45° angle. The hardness of the film is determined by the pencil that damages the coating.

Advantages of the NK system:

• Minimizes operator errors thanks to its pencil holder that ensures constant test parameters.
• Allows quick pencil changes, reducing downtime.
• Suitable for laboratory testing and industrial quality control.

Step-by-step scratch test procedure

1. Prepare and properly clean the surface.
2. Select the pencil according to the hardness scale.
3. Sharpen the pencil before the test.
4. Place the pencil holder on the sample.
5. Adjust the pencil in the corresponding hole until it touches the surface and tighten the side locking screw.
6. Slide the device 6 to 12 mm over the surface, holding the device by the center of the wheels.

Basic NK durometer equipment

The standard kit includes:

• PH1100 pencil durometer.
• 14 pencils with hardness grades: 6B, 5B, 4B, 3B, 2B, B, F, HB, H, 2H, 3H, 4H, 5H, 6H.
• Test pencil holder.
• Pencil sharpener.
• Transport case.
• Optional: additional set with 7H, 8H and 9H pencils.

Which standards does it comply with?

The NK unit ensures compliance with the most demanding international standards:

• UNE EN ISO 15184.
• UNE 48269.
• ASTM D 3363.
• DIN 13523-4.

Benefits of the NK pencil hardness test

• Reliable measurement of surface hardness and scratch resistance.
• Repeatable results thanks to constant angle and pressure.
• Versatility for different types of coatings and industrial sectors.
• Resource optimization: fewer stops and errors reduce material waste.

Frequently Asked Questions (FAQ)

What is an NK durometer and what is it used for?
The NK durometer is a device designed to measure the surface hardness and scratch resistance of paints and coatings using pencils of different hardness grades.

Which pencils do I need to perform a complete test?
The basic equipment includes 14 pencils (6B to 6H), and optionally harder pencils (7H, 8H and 9H) can be added for more demanding tests.

In which industries is the NK durometer recommended?
It is widely used in furniture, automotive, synthetic resins, varnishes and industrial paints, as well as in quality control laboratories.

How can I choose between the NK pencil test and a pendulum test for my application?
If you need to determine scratch resistance and film hardness, the pencil durometer is ideal. To verify the complete curing of paints or coatings, the Persoz or König pendulum is more suitable.