Pulp and Paper Canada

Development of an accelerated curl testing method for mill use

May 4, 2017  By FPInnovations

May 4, 2017 – The market for printing and writing (P&W) paper is becoming increasingly competitive with declining demand. As a result, papermakers are paying more attention to performance in the pressroom.

Researchers from FPInnovations’ Web Performance group were recently asked for help from a member company that was facing curl issues for its P&W paper. In addition to poor appearance of printed paper, curl may cause converting issues at the pressrooms, thus leading to customer complaints and significant production loss. FPInnovations’ expertise was requested in order to develop a uni- form, accelerated curl test to be used by the member company in an attempt to implement a reliable, predictive method for quality control at the company’s mills.

The approach first consisted of understanding the key requirements for a curl testing method to be successfully used at the mills. Following consultation with mills of the member company, it was identified that the curl method should require minimal resources, provide results that are less operator-dependent, and be a strong predictor of end-use curl performance.


FPInnovations experts used their proven, 20-hour in-house curl method to efficiently predict and solve curl issues, as a basis for developing the accelerated curl test. Through modification of the existing method and validation of results, FPInnovations was able to provide an accelerated three-hour testing method by measuring curvature of paper strips upon ambient humidity cycling, without compromising accuracy. Several hours of brainstorming and pooling expertise led to the development of a device that could adapt to various mill situations, while performing efficiently and being cost effective. FPInnovations also offered on-site training and provided support for successful implementation of the method. Benchmarking of papers collected from each mill of the member company validated the accelerated curl testing method and identified further curl improvement opportunities using the new curl testing method.

To date, the testing units have been delivered and installed at two beta sites, leading to an important reduction in customer claims. The two sites are now using this method on a daily basis and the results are very positive. Installation at a third mill is in progress.

For more information, please contact Javad Saberian, researcher in FPInnovations’ Web Performance group, at javad.saberian@fpinnovations.ca.

This column was originally published in the Spring 2017 issue of Pulp & Paper Canada.

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