by DPS Magazine Staff
The recycling of a printed graphic may include de-inking.
De-inking processes are not standardized across the industry and vary regionally. Jeremic says there are three main processes commonly used—alkaline hot wash—using a heated alkaline solution, enzyme-based—using biological catalysts, and flotation—using air bubbles and surfactants.
“In the alkaline hot wash, packaging is placed in a heated alkaline bath. Alkaline agents interact with cured ink to separate it from the substrate. Temperature and use of detergents or surfactants vary between recycling facilities to ensure comprehensive pigment removal,” explains Natasha Jeremic, head of piezo inks, Domino.
Enzyme-based can either be part of the recycling process or a standalone de-inking option. “Enzyme-based de-inking reduces the need for aggressive chemicals. This is particularly well suited to fiber-based materials like paper, because the enzymes specifically target the bonding between cellulose fibers and ink. The enzyme-based approach also works well for plant oil-based inks, where specific enzymes are used to attack the oil,” says Jeremic.
Flotation de-inking, in which air and surfactants separate ink particles from pulp, is another established method that Jeremic considers particularly effective for plant oil-based inks.
Regardless of which of three main processes are used, Dr. Alison Chong, chemistry and materials department manager, Memjet, says de-inking is a critical component of paper and plastic recycling and an important consideration during ink formulation.
“From a materials perspective, inks are most receptive to de-inking when they detach cleanly from the fiber surface and form discrete particles that can be efficiently removed. Highly cross linked or strongly hydrophobic films can be more resistant to separation, which may complicate recovery under standard recycling conditions,” explains Dr. Chong.
Each ink formulation—aqueous, eco-solvent, oil, and UV—has trade-offs in de-inking performance.“Generally, inks that adhere strongly can be more difficult to remove, which can make the previously lauded high durability a challenge for recyclability,” notes Jeremic.
“Aqueous ink features a formulation flexibility that supports cleaner detachment behavior, especially when paired with appropriate primers and substrates,” believes Dr. Chong.
Water-based ink’s lack of water fastness does introduce challenges. “When water is used as the primary washing medium, pigments can dissolve into it, producing colored wash water that can stain or discolor recycled fibers, reducing recyclate quality. As modern water-based inks often contain extremely fine pigment particles to achieve high print quality or run faster, these particles can be difficult to remove and require repeated washing, increasing wastewater volumes,” explains Jeremic.
Solvent-based inks, including eco-solvent, are one of those inks that adhere strongly to substrates, which make them difficult to remove, according to Jeremic.
Oil-based inks, as noted prior, respond well to enzyme-based de-inking. “Enzyme-based de-inking is highly effective for fiber-based materials printed with oil-based inks because the enzymes can specifically target the bonds between cellulose fibers and ink components,” says Jeremic.
Finally, Jeremic says UV-cured inks are among the more challenging to remove because of their highly cross linked, durable, and hydrophobic nature.
Dr. Chong admits that de-inking ability is not determined by ink alone. “The full print construction, including coatings, media, curing conditions, and finishing processes, influences recyclability outcomes.”
Read more on sustainability in ink in Cleaner Printing.
May2026, DPS Magazine
