deinkability

Deinkability is a property of printed paper and mixed fiber streams that describes how easily inks can be removed during recycling. It reflects the effectiveness of the deinking process in separating ink particles from fiber during pulping and subsequent flotation or washing steps, in order to produce pulp suitable for new paper products.

Deinking typically involves pulping the recovered paper, followed by chemical and physical treatments such as washing, surfactant-assisted flotation, and air or froth flotation. Flotation deinking is the most common method in graphic paper recycling, where ink particles attach to air bubbles and rise to the surface to be removed as froth, while the cleaned fibers are recovered for repulping.

Several factors influence deinkability. Ink chemistry and printing technology (toner-based electrophotography, offset inks, inkjet inks, UV-curable inks) affect how easily pigments detach from fibers. Paper substrates, coatings, binders, fiber type, age, and the presence of printed images on coated papers can also affect deinking performance. Advances in inks and coatings continue to challenge deinking in some recycle streams.

Standards and measurement: Deinkability is evaluated with standardized test methods such as the INGEDE deinking protocol, which quantify ink removal efficiency and fiber yield. Other indicators include post-deinking brightness, residual ink content, and the quality of the recovered fiber.

Applications and implications: Recycling mills assess feedstock deinking performance to determine end-use suitability, pulp yield, and product quality. Higher deinkability generally improves recyclate quality, reduces processing costs, and supports environmental goals by enabling more recycled content in paper products. Challenges include evolving inks and coatings that resist ink removal, necessitating ongoing process optimization.