ISO 8791-2

Introducing ISO 8791-2 – Industrial Physics 

ISO 8791-2 is an ISO international testing method that’s used to determine the roughness / smoothness of paper and board using the Bendtsen method.

Bendtsen roughness is a measure of the rate at which air will pass between a flat circular land and a sheet of paper or board. This is when it’s tested under specified conditions and at operating pressure and it’s expressed in milliliters per minute.  

The ISO 8791-2 testing principle

This roughness test and porosity test is based on a leak principle. A paper or paperboard specimen is clamped between a flat glass plate and a circular metal head. Air is then forced through the sample and the rate of airflow between the paper and head is measured in ml/minute. It’s a commonly used roughness testing technique with an adjustable testing time and water pressure.  

This ISO testing method is applicable to paper and board samples which have Bendtsen roughness values between about 50 ml/min and 1200 ml/min. It’s not suitable for soft papers which allow the land to make a significant impression on the surface. It’s also not a suitable roughness testing approach for high-air-permeance papers which allow a significant flow of air to pass through the sheet. The same goes for roughness testing of papers which won’t lie flat under the measuring head. 

Apparatus for ISO 8791-2 bendtsen testing 

There are certain pieces of apparatus that you will need to carry out a successful ISO 8791-2 roughness test, all of which Industrial Physics can provide you with.  

Compressor: the compressor generates air at a pressure of about 127 kPa. Filters can be used to ensure that the air is clean and free from oil.  

Pressure stabilizing reservoir: the pressure stabilizing reservoir shall have a volume of no less than 10 liters, installed between the compressor and the manostat. 

Manostat: the air pressure should be controlled by a manostat at the inlet of the flowmeter. Most bendtsen roughness testing instruments are provided with three interchangeable manostat weights which control air pressure. 

Flowmeter: the flow rate shall be measured by variable-area flowmeters which offer optional flow rate measurements. 

Measuring head: the measuring head consists of an enclosed metal, preferably corrosion-resistant, with an optically flat lower surface. 

Flat plate: a polished flat plate, preferably glass, upon which the test piece is placed for roughness testing. 

Heavy metal weight: heavy metal annulus, or other suitably shaped weight, for keeping the test piece flat around the measuring head.  

ISO 8791-2 bendtsen roughness testing equipment

So, how can Industrial Physics improve your ISO 8791-2 bendtsen roughness testing? 

Technidyne PROFILE/Plus® Bendtsen Roughness with Porosity
The PROFILE/Plus® Bendtsen Roughness with Porosity is a highly-accurate, fully-automated paper roughness and porosity measurement device.  

Technidyne PROFILE/Plus® Roughness Sheffield with Porosity
The Profile/Plus Roughness Sheffield with Porosity accurately and automatically measures surface roughness of paper and air permeance to industry standard methods.  

Need ISO 8791-2 roughness testing solutions? Get in touch

We’ve learnt a thing or two about roughness testing and smoothness testing over the decades. Now Industrial Physics is recognized as a brand that likes to bring new, innovative bendtsen testing equipment to market. 

We like to share our knowledge and we’re here to help you to answer your questions about roughness testing. Across the knowledgebase section of our website we publish lots of blogs on related subjects. For example, why not have a look at this blog that explores the main types of roughness testing? Then you could follow up with this article which delves further into how to test the physical and optical properties of paper. 

If you have any questions about ISO 8791-2 and how we can help you with your bendtsen roughness testing, then please just get in touch!

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Your global test and measurement partner for ISO 8791-2