Tack: Definition and Role in Choosing an Adhesive

Tack: the immediate stickiness power of an adhesive

Tack refers to the immediate stickiness power of an adhesive, meaning its ability to adhere to a surface upon simple contact, without prolonged pressure or waiting time. It is one of the three fundamental properties used to characterize an adhesive in labeling, alongside adhesion, which measures the force required to peel off the label after prolonged contact time, and cohesion, which measures the internal strength of the glue itself against shear stress.

High tack means a label sticks almost instantly as soon as it comes into contact with a surface, even under light and brief pressure. This property is especially sought after on high-speed automated production lines, where the contact time between the label and the product is extremely short, often just a fraction of a second as it passes under an applicator arm. Insufficient tack in this type of application results in poorly fixed labels right from the start, which may partially peel off even before reaching the next stage of the packaging line.

Conversely, a more moderate tack may be desired for certain specific applications, notably repositionable labels or linerless rolls, where too high a tack would encourage unwanted sticking between the roll’s layers or prevent any later repositioning of the label without damaging the surface. The choice of tack level for a product should therefore always be based on the actual usage context, rather than a systematic search for the highest possible tack.

Tack is also sensitive to temperature and the condition of the receiving surface. A cold surface, such as a product coming directly out of a refrigerated chamber, mechanically reduces the effective tack of an adhesive, which explains why applications in cold environments often require adhesives specifically formulated to maintain sufficient tack at low temperatures, like certain Hotmelt adhesives known for their performance under these conditions. Similarly, a dusty, greasy, or wet surface significantly reduces effective tack, regardless of the intrinsic quality of the adhesive used.

For a professional buyer, asking their supplier for details about the tack level of a product, in addition to simply specifying the type of adhesive, allows for a much more precise choice of label according to its real application context, especially when application speed or temperature conditions are critical constraints on the production line involved.