Paper is an incumbent part of many industries. In some industries, it is used as raw material. In other, it is used for packing. And, most importantly, it is used for dissemination of information and promotional materials in the form of magazines, books, newspaper, flyers. Every industry has different specifications as per industrial requirements. Also, the process of recycling helps in repeated use, but this degrades the quality of paper to some extent. How useful this paper is for different industries can be estimated with different tests.
Why is paper testing important?
Without assessing the properties of the raw material, it cannot be incorporated in the production cycle. To evaluate the suitability of the paper for the application, it is important to perform a stringent testing process using machines like Cobb sizing tester, dart impact tester, opacity checker and so on.
Dart impact test
This test determines the behaviour of the paper when an object of specified weight is made to fall free on the specimen. A missile style dart is very important part of this test. It is magnetically attached with the dart holder. To perform the test, the magnetic field is made to vanish by pressing the button. As the magnetic field becomes zero, the dart falls on the specimen clamped on the hollow holder. The machine is designed in such a way that dart follows a straight path when falling from the height without any deviation.
Bursting strength test
In this test, a hydraulic pressure is applied to the sample via rubber diaphragm. The bursting strength tester applies a pressure on the sample until it ruptures. The sample is clamped strategically on the fixture to avoid any slippage during the test. The medium for applying hydraulic pressure is glycerine. Presto offers multiple models of this machines, with data logging feature and computer connectivity. In advanced model, manual clamping is replaced by pneumatic clamping to avoid any slippage of sample.
The gloss reflection of paper is an important quality parameter. Especially when the raw material is being chosen for catalogues and magazines. Now, why you need to assess the gloss value every time you receive the printing material. To avoid the discrepancy. Just imagine, a multi-national producer of paints has got its catalogues published and every batch has different gloss appearance. This reflects the negligence towards the minor quality aspects. To maintain the consistency of the paper throughout, glass value plays a crucial role. Moreover, if the texture of the surface varies the printing would appear differently and thus creates a discrepancy in logos and important brand representing features.
A high-quality paper does not allow the light to pass through it. However, some industries demand paper to be translucent or less opaque. Say, a label of the plastic jar has colourful candies inside, which is the main attraction of the product. Now, the manufacturer wants the translucent label to be published. Any changes in the opacity of the label can impact hugely on the appearance of the packing. Any change in the opacity has to answer by the quality control manager of the labels. Thus, to keep the uniformity in the opacity of the paper, opacity tester plays a key role.
Scuff resistance tester
Due to friction, the labels might lose their prints or may get abraded. Scuff resistance tester checks the friction resistance property of the paper. Along with this, it gives a fair idea about the colour fastening properties as well. The paper which is not coated with the plastic film has comparatively rough surface. The rougher the surface is, the more friction it produces. In this test, two samples of same paper are clamped on the fixture facing each other. The number of rotation is preset. After the test is complete, a visual inspection is done to assess the behaviour of the paper.
Cobb sizing tester
When it comes to paper, Cobb value holds a lot of importance. It tells about the tendency of the paper to retain the absorbed water. This is a very simple test, performed manually. The paper is clamped on the fixture. A Cobb sizing tester has a steel ring cavity to hold the water. This cavity is placed in the paper and leaves to rest for some time. The paper is then removed and excess is water is drained out using stainless steel roller. The difference in weight of the sample before and after the test is Cobb value of paper. As paper is used as raw material for numerous packings, if it retains water, it would affect the contents packed inside.