In the field of printing paper smoothness measurement, the Bekk method and the Bendtsen method are two widely used traditional methods. Both evaluate the smoothness of the paper surface by measuring the rate at which air flows through the gap between the paper and the measuring head under certain conditions, but there are differences in principle, conditions and applicable scenarios. Smoothness directly affects the uniformity of printing ink transfer and print quality, so it is important to choose a method that meets the actual production and quality control needs.
Buick assay
The Buick smoothness meter is based on the "deflated time method". Its core principle is to measure the time it takes for a volume of air to pass through the paper in contact with the ring glass anvil at a certain level of vacuum. The longer the time, the smoother the paper surface and the slower the air leakage. This method is usually suitable for medium to high smoothness paper, and its test conditions are relatively mild and sensitive to the surface structure of the paper. The calculation formula can be expressed as:
Smoothness value = k × t
where t is the deflating time and k is the instrument constant. During the test, the specimen is subjected to a certain pressure to ensure close contact with the glass anvil.
Bentson's assay
The Benterson smoothness meter is based on the "airflow rate method". The core principle is to measure the air flow through the gap between the paper and the measuring head per unit time under a specific pressure difference. The greater the flow rate, the rougher the paper surface and the easier it is for air to pass through. This method is more sensitive to the microscopic unevenness of the paper surface, especially for medium to low smoothness or large roughness. Its measurements are usually read directly in milliliters/minute.
Parameter comparison
| Contrast dimensions | Buick style method |
| Measurement principle | Measure fixed volume air leakage time |
| The results show | Time (seconds) |
| Applicable smoothness range | Medium to high smoothness paper |
| Sensitivity to pressure | higher |
| Test speed | Relatively slow |
| Main criteria: | GB/T 456、ISO 5627 |
| Contrast dimensions | Bent's method |
| Measurement principle | Measures air flow at constant differential pressure |
| The results show | Flow rate (mL/min) |
| Applicable smoothness range | Medium to low smoothness or rougher paper |
| Sensitivity to pressure | Relatively low |
| Test speed | Relatively fast |
| Main criteria: | GB/T 22363、ISO 8791-2 |
Actual selection of printing paper
Which method is more practical to choose requires comprehensive consideration of paper type, printing process requirements and quality control system.
If the main production or use of coated paper, high smoothness offset paper, etc., its smoothness is high, the Buick method can better distinguish its nuances, and its concept of "degassing time" is well related to the "contact closeness" of ink transfer during the printing process, and the data may be more in line with the actual printing suitability evaluation.
If it mainly involves paper types with relatively low smoothness or surface roughness that need to be paid attention to, such as newsprint, writing paper or some packaging cardboard, the special method can more sensitive to reflect the microscopic unevenness of the surface because of its direct measurement of airflow passing ability, which is of practical significance for controlling printing leakage and ensuring uniform ink coverage.
In addition, the actual choice also needs to consider industry practices and supply chain coordination. For example, a particular printing customer or paper specification may explicitly require test data from one of these methods as a basis for acceptance. Laboratory testing efficiency, cost, and historical data accumulation are also practical factors. The Benterson method is typically faster to test and is suitable for production sites that require rapid feedback.
Conclusion
Both the Buick method and the Bentson method are effective methods for determining smoothness, and their applicability depends on the specific application scenario. For the smoothness control of printing paper, it is recommended to first choose the method according to the paper type to which the product belongs and the provisions of mainstream industry standards (such as national standards and customer agreement standards). If the standard allows or conditions are met, a comparative test of the two methods can be carried out to analyze the correlation between their data and the actual printing effect, so as to establish a quality control benchmark that is more in line with their own production reality. Smoothness data can be analyzed in combination with other physical indicators (e.g., roughness, porosity) to provide a more comprehensive assessment of the printability of the paper.
References
1. Determination of smoothness of paper and cardboard (Buick method): GB/T 456-2002[S]. Beijing: China Standard Press, 2002.
2. Determination of roughness of paper and cardboard (Ben Te Sheng method): GB/T 22363-2008[S]. Beijing: China Standard Press, 2008.
3. ISO. Paper and board — Determination of smoothness (Bekk method): ISO 5627:1995[S]. Geneva: ISO, 1995.