Removable, permanent & high-tack adhesives all refer to how strong the glue on the back of your stickers or labels are.
We also refer to them; low, medium, and high strength adhesives.
A popular measure of strength is 'peel adhesion' (read more here). Typical values for each category of adhesive are:
- Removable adhesive = less than 19 N/25mm (1")
- Permanent adhesive = 20-28 N/25mm (1")
- High-tack adhesive = 29 N/25mm (1") and up
The most common adhesive used on stickers & labels is an acrylic, solvent-based, pressure-sensitive adhesive. Pressure-sensitive means they stick more when more pressure is applied.
Manufacturers of self-adhesive label materials will vary the strength of the glue in 2 ways:
- The tackiness of their adhesive
- The thickness of the adhesive
To increase the tackiness, manufacturers use a slightly different adhesive formulation that will stick more.
However, the 2nd way manufacturers vary the strength is through-thickness.; this sounds counter-intuitive, but it works.
Most adhesive coatings on the back of labels are approximately 20 GSM; this can increase to over 40 GSM for heavy-duty purposes. Especially where the surface that's stuck too is rough.
If only 40% of the label's glue touches the surface, adding more adhesive to fill the gaps works brilliantly.
Here's some further reading if you want to learn more about adhesives used for labels & stickers:
- Why do stickers have varying adhesive strengths?
- How do I know what is removable, permanent and high-tack adhesive?