sticky

In papermaking, a sticky is a microscopic to millimeter-scale adhesive particle suspended in recycled fiber stock. These particles originate from labels, pressure-sensitive tapes, hot-melt adhesives used in binding, and coating materials present in waste paper. When paper is pulped, most adhesive dissolves or breaks into discrete fragments; stickies remain tacky and cohesive enough to cause serious processing problems downstream.

Stickies cause two main failures in paper mills. They agglomerate on hot surfaces, particularly on the heated rollers and dryer cans where fiber loses moisture. This buildup deposits as rubber-like residue that marks the sheet with defects and can jam production equipment. More insidiously, stickies deposit inside the paper web itself during sheet formation, creating weak spots that reduce tear strength and surface quality. The problem intensifies during summer months when higher ambient temperatures keep adhesives in a softer, more aggressive state.

Detection and Prevention

Mills manage stickies through a combination of source control and mechanical removal. Better waste segregation before pulping eliminates labels and heavily taped materials. Flotation cells and hydrocyclones can remove some particles during stock cleaning. Sticky traps, typically heated synthetic screens or rotating drums, are installed near the paper machine to catch particles before they reach the sheet. Despite these measures, complete elimination is impossible when processing mixed waste streams.

The term sticky itself is straightforward and reflects the tactile reality: these particles stick. Papermakers distinguish them from other contaminants like sand, staples, and plastic fragments by their adhesive behavior rather than their composition. A single sticky particle measuring 2 to 5 millimeters can compromise an entire roll of lightweight copy paper, making them one of the most economically damaging contaminants in the recycled fiber industry.