This International Standard gives a procedure for determining the curl of paper and board using a vertically suspended test piece, and defines the terms used in curl measurement. This International Standard may be used to measure any curl when - the curl formed approximates the arc of a circle; - the curl is stable enough to remain constant during the time required to cut the test pieces and make the measurement. This primarily includes curl in paper or board as received or after exposure to a constant climatic condition, such as a test room or print shop. NOTE 1 The choice of conditioning climate and conditioning time depends on the purpose of the testing. NOTE 2 For papers coated on one side or gummed-label papers, a period of at least 24 h, after production, should be allowed to permit the paper to stabilize before any curl tests are done.