Curl Tester

Determination of Curl on Paper and Board


TechPap Curl tester - An instrument concept targeted at the accurate detection and measurement of curl
  • The Curt Tester performs static and dynamic measurements of a sample to investigate the kinetics and relaxation phenomena of curl for a short time scale.
  • The sample can be tested at different climate conditions with a RH accuracy of 1% or lower.
  • The instrument is based on the ISO 11556 standard: "Paper and Board Determination of curl using a single vertically suspended test piece".

Figure 1: Curl Tester Chamber
The Device

Why is curl sensing necessary?

The finished production of paper and board may have curl defects which are not immediately apparent upon visual inspection. For certain curl defects to be shown it may be necessary to expose the sample to a change in humidity (either higher or lower humidity). This type of humidity change is very common with storage centers, in warehouses, during shipping or in almost any paper or board application. Humidity can also change in paper or board during printing or converting processes or simply when being used for its intended purpose.
Therefore, it is crucial to know the tendency for a product to curl or twist as soon as possible so that paper machine adjustments can be made to manage the propensity of curl to occur and to maintain quality of the reel.

Application Domains

  • All types of paper and board production including copy papers, coating basepapers, single or multiply board, specialty paper, etc...
  • Improved control of the production processes
  • Development of new products and research for existing products
  • Benchmarking of production for quality control

Figure 2: Test Sample Inside the Test Chamber
Figure 3: Air Humidity Generator


Curl tester brochure in English


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