Pencil Hardness Tester

1. Application

The hardness of a coating film is a critical quality indicator in the paint manufacturing and coating application industries. Since the 1980s, the pencil scratch method has been internationally recognized as a standard testing method for coating hardness. In China, this method has also been widely adopted in coating research and industrial production.

This Pencil Hardness Tester (also called Pencil Hardness Gauge) is designed and manufactured in accordance with the national standard GB/T 6739-2006 “Paints and Varnishes — Determination of Film Hardness by Pencil Test”. The instrument can be used both in laboratories and on construction sites, and it allows hardness testing of coatings in any direction.

2. Technical Specifications

3. Operating Instructions

Sample Preparation: Typically, a smooth tinplate panel (120 × 50 × 0.2–0.3 mm) is used, or a substrate specified by the product standard.

Pencil Preparation: Carefully remove the wood around the pencil tip with a sharpener to expose a 3 mm cylindrical lead core. Avoid loosening or damaging the lead.

Instrument Setup: Place the tester on a flat surface. Insert the prepared pencil into the holder at a 45° angle so that the pencil edge contacts the surface. Tighten the screw to secure the pencil.

Testing Procedure: Place the tester on the coated sample. Apply uniform force so that the pencil tip either scratches or indents the coating. Move the tester forward at 1 mm/s. Start with the hardest pencil and draw five scratches, each about 3 mm long, with each grade of pencil.

Result Evaluation: The hardest pencil that does not damage the coating surface indicates the coating hardness, in accordance with GB/T 6739-2006 standards.

4. Maintenance & Care

After each test, clean the instrument thoroughly.

Store the tester in its protective case in a dry environment.

Avoid moisture or contamination to ensure long-term precision.