Bendtsen Smoothness and Porosity Tester for Paper

What is the Bendtsen Smoothness and Porosity Tester for Paper?

A Bendtsen instrument measures surface roughness and air permeability from the rate of air flow over or through the sheet under a defined pressure difference. Both parameters relate to print quality and to ink penetration in printing and coating grades.

Overview

In the roughness mode, a circular measuring ring is pressed against the sheet under a defined load and air flows between ring and surface, so a rougher sheet passes more air. In the porosity mode, air flows through a defined area of the sheet at a set pressure difference and the volume rate is recorded. Both measurements need clean surfaces, a stable pressure source and reference standards, namely calibrated plates of known roughness and perforated discs of certified air flow, used to check each scale. Results are displayed as roughness in micrometres and permeability in millilitres per minute, and conditioning the specimen is essential because both properties change with moisture.

How does it work?

Mechanical paper tests apply a controlled force or deformation to a conditioned specimen and record the load or the extent of damage. Tensile testing pulls a strip at constant rate and records breaking force, elongation and tensile energy absorption, from which indices are calculated using basis weight. Tearing resistance is measured by the energy absorbed when a specimen with a pre-cut slit is torn by a pendulum or a falling weight. Folding endurance counts the number of double folds a strip withstands under tension before it breaks. Surface and absorbency tests use different principles: water absorbency is determined by the mass of water taken up by a defined area during a timed contact, smoothness by the air flow between a measuring ring and the sheet surface, and porosity by the air flow through the sheet itself at a defined pressure difference.

What are the key features?

• Measuring ring for surface roughness
• Defined pressure difference for air permeability
• Certified reference plates and perforated discs
• Stable air supply with filter and regulator
• Digital display with statistics
• Separate heads for the two measurements

What are the technical specifications?

A typical bendtsen smoothness and porosity tester for paper configuration offers roughness range of 0.1–4.0 µm, roughness resolution of 0.01 µm, air permeability range of 0.1–1000 mL/min, pressure difference of 1.47 kPa roughness, 1.0 kPa porosity, measuring ring load of Per the method and reference standards of Calibrated roughness plates and orifices. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Bendtsen Smoothness and Porosity Tester for Paper is used in print quality assessment of coated papers, smoothness control for gravure and offset printing, air permeability checks of filter and vent papers and process control after calendering. Across the wider Paper Quality Analysis class, laboratories also deploy it for tensile strength and elongation of packaging papers, tearing resistance of sack, tissue and bound papers and water absorbency of sizing and coating grades.

Which standards and certifications apply?

Relevant standards and methods include ISO 1924-2, ISO 1974, ISO 535, ISO 8791-2, ISO 5626, ASTM D828, TAPPI T494, TAPPI T414, TAPPI T441 and IEC 61010-1. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Condition specimens to the standard atmosphere, usually 23 °C and 50% relative humidity, before every mechanical test, because strength properties change sharply with moisture. Cut specimens with sharp dies or blades and reject those with damaged edges, since a nick initiates premature failure. Keep grips clean and aligned, and verify load cells with certified masses or a reference load cell at defined intervals. For absorbency and surface tests, control the water temperature, contact time and pressure difference, and clean measuring rings and plates, because deposits change the flow. Record basis weight, test direction, specimen count and conditioning with every result so that indices can be recalculated.

How do I select the right Bendtsen Smoothness and Porosity Tester for Paper?

Choose a Bendtsen instrument when the specification names roughness and air permeability, which is common for printing papers and filter media. Confirm the range covers both your smoothest and your roughest grades, and check the availability of certified reference plates and orifices for routine verification of each scale.

How does it compare with other Paper Quality Analysis variants?

Select the test that corresponds to the specification you must meet and to the failure mode you are investigating. Tensile testing is fundamental for packaging, bag and label papers because it defines strength in the principal load direction. Tearing resistance is important for papers that are handled, punched or bound, and for tissue and sack grades. Internal bond, folding endurance and tensile energy absorption matter for papers that are creased or repeatedly flexed. Water absorbency is specified for papers that are glued, coated or used outdoors, while smoothness and porosity are specified where print quality and ink penetration matter. Each instrument should be capable of the exact conditions named in the standard, since test length, strain rate and contact area change results appreciably.