Air Permeance
Measurement of the resistance offered by paper or board to the passage of air under specified pressure conditions provides the objective foundation for iso 5636-3. This method uses the Bendtsen test apparatus to quantify how much air travels through a sheet in a fixed duration when the material is clamped between circular land areas of a defined width. It specifically governs substrates with a high degree of porosity where low resistance values facilitate quick throughput in air flow detectors.
Measurement Protocol
Technicians place the sample on a clean glass plate and lower the measuring head to create a seal against the surface. The device introduces air from a pressurized reservoir and directs the flow through the annular test area into the specimen. A sensor records the rate of volume displacement at a standard pressure difference of one point four seven kilopascals.
Calibrating the air supply line prevents internal friction from skewing the final reading. Proper seating of the weight ensures the contact ring prevents lateral leakage at the edge of the gasket.
Production Variance
Variations in fibre orientation or density across the web change the transmission rate recorded by iso 5636-3 during routine quality audits. Converters monitor these changes because excessive porosity affects the performance of vacuum transport systems and high speed suction feeders on printing presses. If a batch exhibits values outside the target range, the risk of misfeeds or registration errors increases during automatic processing cycles.
A stable outcome provides assurance that the substrate remains uniform enough for consistent vacuum draw during industrial handling.
