The purpose of this method is to separate contaminants such as shives in mechanical pulp, and stickies, plastics, sand, metal pieces, and flakes in recycled fiber from pulp fibers for subsequent examination and/or quantification. This method employs a screening device and the separation is based on size difference between fibers and contaminants. However, depending on their flexibility and/or geometry, not all of the contaminants that are larger in size than fiber can be captured by the screen. The dimensional limits that separate contaminants from fibers, as well as the time length of screening are arbitrary. Screen plates of various slit widths such as 0.10 mm, 0.15 mm, 0.20 mm, and 0.25 mm have been used in separating contaminants. Only the use of 0.15 mm slit is covered in detail in this method.