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GRA324 Cobb Test 11 Instrumentation .docx

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Graphic Communications
GRA 324
Chris Kular

Test11 Water Absorption of PaperCobb TestTheoryConcept Paper has varying degrees of porosity due to its composition of unsystematic felted layers of fibre Its composition therefore allows for different states of matter such as liquids and gases the ability to penetrate through a papers structuremaking this property highly significant to the use of paper Ballarpur Industries Limited nd For this test the apparatus called the Cobb Tester will be used to measure the resistance of a paper towards the saturation of aqueous solutionwater which is important for many paper applicationsDefinitions In Regards to Test Water absorbencya measure of the amount of water absorbed by the wetted surface of paper and board materials Leatherdale nd Sizingthe treatment of paper with materials or chemicals to impart the resistance to water oils and other fluids to seal down its surface fibers and to improve its surface strength Wilson 1998 Expected Outcomes and Educational GainsIt is expected that all of the different types of paper will increase in weight due to the water absorbed by the papers fibres Also just by knowing the paper types we can hypothesize that the uncoated papers will have a lesser mass compared to coated The Water Absorption of Paper test shows just how much water is retainedabsorbed and the educational gain is that the degree of sizing that is done to a paper affects whether or not it will have a high or low resistance to water penetration Wilson 1998Importance of testPaper manufacturers have to meet the technical requirements of the papermaking process in order for different types of paper to be reproduced in a way that meets a customers expectations Sizing is one of those requirements There exists three kinds of sizing which can be internal external or surfacesized Sizing materials include starch and rosin which can be added internally externally or both Internal sizing gives paper water resistance while rosin and papermakers alum are used commonly for internal sizing Surface sizing on the other hand controls the absorption of printing ink allowing better and crisper images on the paper surface DejidasDestree 2005The paper manufacturer should know which methods to apply when making paper suitable for different purposes such as packaging paper that requires it to be
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