Introduction

ASTM International develops and publishes technical standards for a wide range of materials, products, and systems. 

Among these, ASTM D645 is a critical standard used to determine the thickness of paper and paperboard. This test 

method ensures consistency, quality control, and compliance in the paper manufacturing and packaging industries.

Scope and Significance of ASTM D645

ASTM D645 provides a standardized procedure for measuring the thickness of paper and paperboard under specified 

conditions. Thickness is a fundamental property that affects the material’s strength, stiffness, and performance in 

various applications, such as packaging, printing, and labeling.

Accurate thickness measurement is essential for:

Quality Control – Ensuring uniformity in production.

Product Performance – Meeting specifications for durability and functionality.

Regulatory Compliance – Adhering to industry and customer requirements.

Testing instruments:PTT-03 Thickness Tester

Test Procedure

The ASTM D645 test method involves the following key steps:

Sample Preparation – Cut representative samples of paper or paperboard to the required dimensions, ensuring they 

are free from wrinkles, folds, or defects.

Conditioning – Condition the samples in a controlled environment (typically 23°C ± 1°C and 50% ± 2% relative humidity) 

to achieve equilibrium before testing.

Measurement – Use a calibrated micrometer or thickness gauge to measure the sample at multiple locations, applying 

a specified pressure (usually 50 kPa or 7.25 psi).

Calculation – Record the average thickness from multiple readings to ensure accuracy.

Factors Affecting Thickness Measurement

Several factors can influence the results of ASTM D645 testing:

Moisture Content – Paper thickness can vary with humidity.

Pressure Applied – Excessive or insufficient pressure can lead to inaccurate readings.

Instrument Calibration – Proper maintenance of measuring devices is crucial for reliable data.

Applications of ASTM D645

This standard is widely used in industries such as:

Packaging – Ensuring corrugated boards meet strength requirements.

Printing – Maintaining paper thickness for optimal print quality.

Consumer Products – Verifying the thickness of paper-based materials in food packaging, labels, and more.

Conclusion

ASTM D645 plays a vital role in maintaining quality and consistency in paper and paperboard products. By following

 this standardized test method, manufacturers and testing laboratories can ensure that materials meet performance 

expectations and industry specifications. Proper thickness measurement contributes to product reliability, customer 

satisfaction, and efficient production processes.

For more detailed information, refer to the official ASTM D645 standard documentation.