Pulp Freeness Testing
Channel: Kevin Martin
Date: 2014-08-05

This video shows a quick demonstration of how paper pulp freeness is tested using two common pieces of lab apparatus: A Canadian Standard Freeness (CSF) Tester and a Schopper-Riegler (S-R) Tester.

Pulp freeness is a measure of how quickly the water can drain from the pulp when a sheet of paper is being formed. The freeness is reduced if the pulp is either very hydrated (so that a lot of the water is actually bound to the pulp and does not drain off) or very fine (so that it clogs the drainage flow more quickly).
Processing the pulp in a Hollander beater helps to hydrate the fibres and make them finer, which allows them to bond more securely in the finished paper to produce a stronger and crisper paper. The freeness tester provides a way to measure the progress of beating.

I explain the general principal of these tests and demonstrate the use of the testers. To obtain truly accurate results the testers should be installed and properly leveled, and the temperature of the pulp sample should be checked. For the CSF test there are tables to convert results taken at nonstandard temperature or fibre quantity to standardized values. There is also a rough conversion between ml of CSF and °SR.

My blog post relating to this video is located at
http://www.papertrail.ca/blog/2014/08/04/freeness-testing-demonstration/