Why is wastepaper de-inked before it is used for printing-grade paper?

Wastepaper is de-inked before it is used for printing-grade paper to ensure the final product meets the necessary quality and aesthetic standards for printing applications.

When wastepaper is processed for high-quality uses, such as printing-grade or other white papers, the presence of printing inks and other foreign materials must be removed to achieve the desired whiteness and purity. During the de-inking process, the wastepaper is pulped with hot water and chemicals—most commonly caustic soda—to separate and disperse the ink from the cellulose fibres. Following this, the stock is washed to remove the dispersed ink and chemicals, and in some cases, it is further bleached to improve its whiteness.12

In contrast, recovery processes for lower-quality products like boxboards or coarse papers do not require de-inking, as the presence of ink does not interfere with the functional requirements of those materials.1