The TAPPI T 558 standard specifies a method for determining the surface wettability and water-absorption of sheet materials (e.g. paper, Cardboard, etc.) using an automatic contact angle tester. This method evaluates the ability of liquids to adhere or wetting the sheet surface and the degree to which liquids are absorbed by the surface by measuring the contact angle of droplets on the surface of the material. The contact angle ranges from close to 0 ° to close to 180 ° and is suitable for a variety of liquids and sheet materials. This standard is widely used in papermaking, printing, Encasement and other industries to optimize paper coatings, evaluate paper printability, test paper waterproof performance, etc., to help improve product mass and process control.